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1

Comparison of ultrasonic and other atomization methods in metal powder production

Bałasz B., Bielecki M., Gulbiński W., Słoboda Ł.

Journal of Achievements in Materials and Manufacturing Engineering

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2023

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Vol. 116, nr 1

11--24

EN

Purpose: Additive manufacturing (AM) research needs new alloys to grow and offer new functionalities. This paper presents a novel powder production method by means of ultrasonic atomisation (UA). Powders for AM can be obtained from gas atomisation (GA) and a comparative study of UA- vs GA-made powders were carried out. To UA explain the pros & cons more clearly, a summary of the processes was added, along with the analysis of the droplet formation physics. Design/methodology/approach: Ultrasonic atomization (UA) with melting raw material by an electric arc. Characterisation of the powders: particle size distribution (PSD), density, and flowability were carried out. Other parameters, such as microstructure, deviation in the chemical composition and powder surface morphology, were also investigated. Findings: The results showed that the UA powder has a finer average particle size with a narrower statistical distribution of particles than those made by the GA method. Because the UA powder has a higher sphericity and lower porosity, Generally, UA offers better-quality powders in terms of properties such as higher tap density, better flowability and low oxygen content. Research limitations/implications: As an example of semi-industrial scale application of the UA system, the Ti6Al4V and TiAl powders were produced after remelting the wire. The UA system is commercially available for processing any metallic material. Practical implications: The test campaign results showed that the Ti6Al4V powder produced by the ultrasonic atomisation has a similar or better quality as those available from large-scale gas atomisation plants. Originality/value: The new method of UA powder production was analysed in terms of key powder parameters. The properties of the titanium-based powder produced this way were analysed with a view to future applications.

2

Thermomechanical processing of CuTi4 alloy

Rdzawski Z., Stobrawa J., Głuchowski W., Konieczny J.

Journal of Achievements in Materials and Manufacturing Engineering

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2010

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Vol. 42, nr 1-2

9-25

EN

Purpose: One of the reasons behind the interest in copper titanium alloys was development of new materials to substitute copper beryllium alloys. The reason for selecting that material for studies was that in the early stages of decomposition of CuTi4 alloy a spinodal transformation takes place and ordering processes begin. Proper selection of heat treatment and plastic working conditions provides possibilities to produce very wide range of sets of properties by formation of the required alloy microstructure. Therefore the main objective of the study was to capture the changes in precipitation kinetics, especially in the relations between supersaturation and ageing or between supersaturaion, cold deformation and ageing in connection to the changes in microstructure and functional properties (mainly changes in hardness and electrical conductivity). Design/methodology/approach: Melting of the charge material was conducted in medium-frequency induction furnace, in a graphite crucible. The melted material after bath preparation was poured into a cast iron ingot mould (with graphite grease applied on the inside) of dimensions 35 x 120 x 250 mm. The ingots after casting were peeled. The treated ingots were heated in resistance furnace at 900şC for 1.5 hour and rolled down on a reversible two-high mill. Findings: Decomposition of supersaturated solid solution in that alloy is similar to the alloys produced in laboratory scale. The observed differences in microstructure after supersaturation were related to the presence of undissolved Ti particles and increased segregation of titanium distribution in copper matrix including microareas of individual grains. The mentioned factors influence the mechanism and kinetics of precipitation and subsequently the produced wide ranges of functional properties of the alloy. Research limitations/implications: Cold deformation (50% reduction) of the alloy after supersaturation changes the mechanism and kinetics of precipitation and provides possibilities for production of broader sets of functional properties. It is expected that widening of the cold deformation range should result in more complete characteristics of material properties, suitable for the foreseen applications. Similar effects can be expected after application of cold deformation after ageing. Practical implications: The elaborated research results present some utilitarian qualities since they can be used in development of process conditions for industrial scale production of strips from CuTi4 alloy of defined properties and operating qualities. Originality/value: The mentioned factors influence the mechanism and kinetics of precipitation and subsequently the produced wide ranges of functional properties of the Cu-Ti alloys.

3

The microstructure and properties of the bainitic cast steel for scissors crossovers

Pacyna J., Bała P., Dobosz S., Kokosza A., Kąc S.

Journal of Achievements in Materials and Manufacturing Engineering

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2010

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Vol. 39, nr 1

19-26

EN

Purpose: The main purpose of the hereby study was the description of microstructure and properties of the new low-carbon Mn-Cr-Mo-V-Ni bainitic cast steel developed in the AGH Laboratory of Phase Transformations for cast mono-blocks of scissors crossovers. Investigations comprise material in as-cast state and after various variants of normalization as well as normalization and high tempering. Design/methodology/approach: Analyses of microstructure, strength properties, impact toughness and crack resistance (KIc) were performed both for material in the as-cast state and after heat treatments. The influence of the initial microstructure on the investigated cast steel hardness – after the normalizing and after the normalizing and tempering – was determined. Findings: Changes in the microstructure of the cast bainitic scissors crossovers were determined and their properties described. Research limitations/implications: The investigations were performed in order to estimate a possibility of applying bainitic cast steels for production of scissors crossovers in the form of monolithic blocks. Practical implications: Application of bainitic cast steels for scissors crossovers in the form of monolithic blocks. Originality/value: Designing of the chemical composition of the bainitic cast steel (Mn-Cr-Mo-V-Ni) and its heat treatment.

4

The influence of heat treatment on microstructure and crack resistance of boron microalloyed steel plates

Opiela M.

Journal of Achievements in Materials and Manufacturing Engineering

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2010

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Vol. 43, nr 1

117-124

EN

Purpose: The work presents results of investigation of heat treatment conditions influence on microstructure and crack resistance of C-Mn constructional steels with microaddition of boron assigned to be used in production of high strength steel plates. Design/methodology/approach: Metallographic observations, heat treatment, hardness measurements, impact strength examinations, fractographic analyses of fracture surfaces of test pieces have been performed. Findings: Dispersive particles of interstitial phases formed on dislocations during the plastic deformation, limiting grain growth of austenite, create the possibility to obtain metallurgical products with fine-grained microstructure giving them high strength and guaranteed crack resistance, also at low temperature. Research limitations/implications: Further research of microstructure in transmission electron microscope as well as complementary impact resistance tests at the temperature lower than -60°C are foreseen to be performed. Practical implications: Obtained results of examinations, especially detailed fractographic analysis of fracture surfaces of test pieces together with chemical composition analysis of revealed non-metallic inclusions and precipitations of secondary phases will make contribution to better understanding of cracking mechanisms in the group of high-strength steels. Originality/value: Performed research revealed that investigated steels present high crack resistance also at low temperature. It can be achieved through proper selection of chemical composition and adequate conditions of heat treatment and plastic working. The presence of microadditions of transition metals deriving from IVb and Vb group of periodic classification of the elements with high chemical affinity to nitrogen and carbon allows producing rolled products with high exploitation properties. Keywords: Metallic alloys; Heat treatment; Microalloyed steels; Heavy plates; Crack resistance

5

Prevention methods against hydrogen degradation of steel

Ćwiek J.

Journal of Achievements in Materials and Manufacturing Engineering

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2010

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Vol. 43, nr 1

214-221

EN

Purpose: of this paper is presentation of mechanisms and forms of hydrogen degradation in steel along with pointing out methods for hydrogen degradation prevention. Design/methodology/approach: Hydrogen degradation of steel is a form of environmentally assisted failure which is caused by the action of hydrogen often in combination with residual or applied stress resulting in reduction of plasticity, load bearing capacity of a component, and cracking. Findings: The sources of hydrogen in steel were presented. Forms of hydrogen presence in metals, mechanisms of hydrogen degradation, and types of hydrogen induced damage were discussed in details. Five specific types of hydrogen induced damage to metals and alloys could be distinguished: hydrogen embrittlement, hydrogen-induced blistering, cracking from precipitation of internal hydrogen, hydrogen attack, cracking from hydride formation. Practical implications: Methods for hydrogen degradation prevention include: selection of suitable material, modifying environment to reduce hydrogen charging, and use of surface coatings and effective inhibitors. Originality/value: Originality the paper outlines the problem of hydrogen degradation of steel and other alloys, delivering knowledge to undertake preventive or remedial actions in order to avoid hydrogen induced degradation.

6

Morphological features of retained austenite in thermo-mechanically processed C-Mn-Si-Al-Nb-Ti multiphase steel

Grajcar A.

Journal of Achievements in Materials and Manufacturing Engineering

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2010

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Vol. 39, nr 1

7-18

EN

Purpose: The aim of the paper is to determine the influence of isothermal bainitic transformation temperature on morphological features and a fraction of retained austenite in a new-developed thermo-mechanically processed C-Mn-Si-Al-Nb-Ti multiphase steel. Design/methodology/approach: The thermo-mechanical processing was realized in a multi-stage compression test by the use of the Gleeble thermomechanical simulator. The steel was isothermally held for 600 s in a bainitic transformation temperature range of 250 to 500°C. A fraction and stereological parameters of retained austenite were determined by a computer image analyser using an optical microscope. The details of the retained austenite morphology were revealed in a scanning electron microscope and using EBSD technique. Findings: The maximum fraction of retained austenite (above 14%) was obtained for the temperatures of isothermal bainitic transformation from 400 to 450°C. Below 350°C, the largest grains of retained austenite located in a ferritic matrix transform to martensite and its fraction estimated by the use of computer image analysis is too high compared to X-ray investigations. Blocky, irregular grains located in a ferritic matrix are a main structural constituent of retained austenite in a temperature range up to 350°C. Increasing the isothermal holding temperature to a range of 400-450°C results in increasing a fraction of fine blocky and layer regions of the ă phase. Research limitations/implications: To describe in detail morphological features of retained austenite in fine-grained multiphase structures, a combination of different methods characterized by various resolution is necessary. Practical implications: The revealed morphological features of retained austenite are of great importance for mechanical stability of this phase during cold straining, affecting mechanical properties of advanced TRIP-assisted steels. Originality/value: Combined colour etching, scanning electron microscopy and EBSD (Electron Backscattered Diffraction) methods were applied to characterize retained austenite in a modern group of thermomechanically processed TRIP steels with Nb and Ti microadditions.

7

Micro-forming of Al-Si foil

Haga T., Inoue K., Watari H.

Journal of Achievements in Materials and Manufacturing Engineering

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2010

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Vol. 40, nr 2

115-122

EN

Purpose: of this paper is as below. The investigation of the ability of the cold micro-forming of non-metallic glass was purpose. The grain of the rapidly solidified aluminium alloy became fine. The aluminium alloy foil with fine grain was used, and the investigation of the micro-formability of this alloy was investigated. Moreover, increase of the forming speed was investigated. The increase of the forming speed was purpose of this study, too. Design/methodology/approach: The nozzle pressing melt spinning method was used to attain the rapid solidification of the non-metallic grass. The Al-14mass%Si, which is hyper eutectic but is close to eutectic, was used. The roll contact surface was formed by V-groove. The cold rolling was adopted for forming. The V-groove was machined at the roll surface. The micro-forming was operated at the cold work. Findings: Micro-forming of the crystal aluminium alloy was able by the cold work. The forming speed was 0.04S to form 10 ěm height. The forming speed could be drastically increased. Research limitations/implications: The angle of the V-groove, which was used in the present study, was only 60 degrees. The effect of the groove angle on the protrusion-height was not clear. The used material was only the Al-14mass%Si. Relationship between the material and protrusion-height was not clear. Practical implications: The die for the micro-forming of the resin could be made from economy material by the conventional cold rolling process at short time. Therefore, the mass production of the economy die for resin may be obtained. Originality/value: The micro-forming of the rapidly solidified non-metallic glass by cold work was original.

8

Investigations of microstructure and dislocations of cast magnesium alloys

Tański T., Dobrzański L. A., Labisz K.

Journal of Achievements in Materials and Manufacturing Engineering

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2010

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Vol. 42, nr 1-2

94-102

EN

Purpose: The microstructures and the dislocation arrangements in the cast magnesium alloy have been investigated using transmission electron microscopy and high-resolution transmission electron microscopy. In this paper are presented also the results of phase morphology investigation of an new developed Mg alloy. Such studies are of great interest for the metal industry, mainly the automobile industry, were the improvement of cast elements quality is crucial for economic and quality reason and depends mainly on properly performed controlling process of the production parameters. There are presented especially the effect of heat treatment on the size and distribution of the precipitation occurred in the matrix. Design/methodology/approach: The basic assumptions of this work are realised an Universal Metallurgical Simulator and Analyzer. The solidification process itself is analysed using the UMSA device by appliance of the Derivative Thermo Analysis. The thermal analysis was performed at a low but regulated cooling rate in a range of 0.2 oC to ca. 3 oC. Cooling curve for the thermal analysis was performed using a high sensitivity thermocouples of the K type, covered with a stainless steel sheath. The data were acquired by a high speed data acquisition system linked to a PC computer. Two different types of samples were used, bulk-cylindrical, and thin-walled cylindrical. Metallographic investigation were made on cross section samples of a engine bloc. Non-equilibrium heating and cooling process conditions were applied to achieve changes in shape and distribution of the phases such as Al2Cu and Si. Findings: During the investigation Dislocation networks are found to increase with deformation in all cases. The dislocation networks have been found in the g- Mg17Al12 phase as well as in the matrix in the investigation magnesium alloys. The crystallographic orientation relationship are: (1 01) .-Mg Ś (10 ) Mg17Al12 and [11 0] .-Mg Ś [111] Mg17Al12. Precipitation of the g-Mg17Al12 phase are mostly of the shape of roads, and the prevailing growing directions are the directions <110> .-Mg. Research limitations/implications: The investigations were performed using standard metallographic investigation as optical, scanning and transmission electron microscopy methods, also electron diffraction methods were applied for phase identification. Originality/value: The originality of this work is based on applying of regulated cooling rate of magnesium alloy for structure and mechanical properties changes. In this work the dependence between the regulated heat treatment, chemical composition and structure of the investigated magnesium cast alloy on the basis of the structure investigations was presented.

9

Image analysis used for aluminium alloy microstructure investigation

Krupiński M., Labisz K., Dobrzański L. A., Rdzawski Z.

Journal of Achievements in Materials and Manufacturing Engineering

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2010

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Vol. 42, nr 1-2

58-65

EN

Purpose: In this work the metallographic microstructure analysis of the investigated AlSi7Cu3Mg aluminium cast alloy was performed for samples cooled with different cooling rate settings. The preformed investigations are subjected to the analysis of cooling rate influence on the phase morphology. Design/methodology/approach: The solidification process itself is analysed using the UMSA device by appliance of the Derivative Thermo Analysis. The influence of the cooling rate on the alloy microstructure was investigated using computer aided image analysis, in this work also the content of particular phases was analysed, as well the percentage of pinholes compared to the chosen cooling rate. Findings: The treated sample is without holes, cracks and defects as well as has a slightly higher hardness value compared to the as-cast material. Research limitations/implications: The investigated samples were made of the cylindrical shape and were cooled in the range of 0.2°C/s to 1.25°C/s. In this work also the derivative thermoanalysis was performed to determine the correlation between the chosen cooling rate and the microstructure as well changes in the derivative curve shape. For alloy cooling with chosen cooling rate as well for the derivative thermo-analysis the UMSA analysator was applied. Practical implications: The investigated material can find its use in the foundry industry; an improvement of component quality depends mainly on better control over the production parameters. Originality/value: The originality of this work is based on applying of regulated cooling rate of aluminium alloy for structure and mechanical properties changes. As an effect of this study it will be possible to understand and to influence the mechanism of structure forming, refinement and nucleation. Also a better understanding of the thermal characteristics will be provided to achieve a desirable phase morphology required for application of this material under production conditions.

10

Derivative thermo-analysis application to assess the cooling rate influence on the microstructure of Al-Si alloy cast

Krupiński M., Labisz K., Dobrzański L. A., Rdzawski Z. M.

Journal of Achievements in Materials and Manufacturing Engineering

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2010

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Vol. 38, nr 2

115-122

EN

Purpose: The application of the UMSA device (Universal Metallurgical Simulator and Analyzer) has allow to determine the liquidus/solidus thermal points of solidified alloy, as well the thermal points, where phase- or eutectic crystallisation occurs. Design/methodology/approach: Investigations were performed using cast aluminium-silicon alloys, known as EN AC-4XXXX according to the PN-EN 1706:2001 standard. The solidification process was investigated using the metallurgical UMSA simulator connected to recording devices equipped with simulating cooling system. For the alloy microstructure investigation the optical microscope and transmission and scanning electron microscope with EDS equipment were used for evaluation of the chemical composition of the phases occurred in the investigated alloy. Findings: Investigation of the interdependences occurred between phase morphology and cooling rate using thermo-analysis has given the main results. Practical implications: In the metal casting industry the improvement of the quality of components depends mainly on proper control over the production parameters. Originality/value: The performed investigations allow to determine the microstructure changes as well the derivative curves in comparison to the cooling rate applied for the alloy.

11

Crystallization kinetics of Zn alloys modified with Ce, La, Sr, Ti, B

Krupińska B., Labisz K., Dobrzański L. A., Rdzawski Z.

Journal of Achievements in Materials and Manufacturing Engineering

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2010

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Vol. 42, nr 1-2

50-57

EN

Purpose: This paper presents the investigation results of cooling rate influence on microstructure of the Zn-Al cast alloy. Thermo-derivative analysis of the investigated alloys was performed using the UMSA device (Universal Metallurgical Simulator and Analyzer). This device makes it possible to characterise the important points of the crystallised alloy diagram including: phase and eutectics crystallisation, as well liquidus/solidus points. The material used for investigation was the ZL8 alloy. Design/methodology/approach: Moreover the analysis of cooling rate influence on the derivative curve changes was performed as a result of the measured crystallisation kinetic changes. For the assessment of the cooling rate influence on the mechanical properties also hardness measurements were performed using the Rockwell hardness device. Findings: The treated sample is without holes, cracks and defects as well as has a slightly higher hardness value compared to the as-cast material. Research limitations/implications: Microstructure and mechanical properties investigations of the investigated alloy was performed for the reason of alloying additives influence on alloy microstructure and properties change, the microstructure was analyzed qualitatively using light and scanning electron microscope as well as the area mapping and point-wise EDS microanalysis. The performed investigation are discussed for the reason of an possible improvement of thermal and structural properties of the alloy. Practical implications: The investigated material can find its use in the foundry industry; an improvement of component quality depends mainly on better control over the production parameters. Originality/value: This work provides better understanding of the thermal characteristics and processes occurred in the new developed alloy. The achieved results can be used for liquid metal processing in science and industry and obtaining of a required alloy microstructure and properties influenced by a proper production condition.

12

Computer models of steam pipeline components in the evaluation of their local strength

Okrajni J., Essler W.

Journal of Achievements in Materials and Manufacturing Engineering

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2010

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Vol. 39, nr 1

71-78

EN

Purpose: The paper discusses the issue of modelling the heating and cooling processes of T-pipes in a power plant pipeline in the start-up conditions of a boiler. The main purpose of this work is the description of the mechanical behaviour of power plant components working under mechanical and thermal loading and validation of the computer modelling methods. Design/methodology/approach: The FEM modelling has been used to describe the local stress-strain behaviour of the chosen component. Findings: The reasons for the presence of high and variable in time temperature gradients in the components of the main steam pipeline include, among other things, variable values of the coefficient of heat transfer between the pipeline material and the medium flowing inside it, which, at this stage of boiler operation, may change its state. Unsteady operation of a pipeline, especially in case of subsequent boiler start-ups, may induce thermal stresses which exceed the values of allowable stress in components of complex shapes. Research limitations/implications: The possibility of applying the durability criteria currently assumed in standards still requires justification and confirmation in laboratory and industrial conditions to be closer to the real components behaviour. In such situation the presented analysis is the part of the complex investigation method which main purpose is increasing accuracy of the TMF process description and thermo-mechanical life assessment. Practical implications: The calculations carried out may constitute a basis for developing a material test parameters which would bring closer the fatigue conditions appearing locally in the analysed components. The method of stress-strain behaviour analysis used in the paper could be useful in the practical cases when the real components mechanical behaviour would be analysed. Originality/value: The main value of this paper is the own method of the mechanical behaviour analysis of the power plant component. This method includes the temperature fields analysis taking into account the boundary conditions based on the operation parameter data and the thermoplastic material model. The material stress-strain behaviour has been treated as the local phenomenon, that could be modelled by FEM.

13

Thermovision systems used to improve a technological process for hot-rolled copper and brass strips

Rdzawski Z., Krupińska B., Musztyfaga M.

Journal of Achievements in Materials and Manufacturing Engineering

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2009

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Vol. 36, nr 2

115-125

EN

Purpose: This paper contains description made on thermovision testing with the use of Inframetrics 760B system. Measurements were executed on the surface of a heat furnace and also on the surface of material heated before and hot-rolled. The results of the investigations in a form of thermograpic pictures were taken down in working environment. Design/methodology/approach: The purpose of this research was to evaluate technological process of heating cooper and brass cakes, and hot-rolled strip in special passes assessment of the temperature modification. For basic criterion estimation of these processes, the maintenance at the demanded final rolling temperature in order to keep up adequate structure and narrow range of mechanical properties variation was accepted. Findings: The process of heating charge material is carried through in order to facilitate its machining in a rolling process. When the material does not obtain the adequate temperature or does not become uniformly heated, internal stresses which cause appearance of the rims of fracture and occurrence of other defects in structure appear in cold rolling, as the next. Because of this there is a need of temperature controlling. Research limitations/implications: If a temperature profile on heated to a hot-rolled cakes is not uniform and does not reach a given level, this can mean forming some defects, which can be revealed during a hot-rolled process, relatively during following technological operations leading to a quality decrease and in a consequence to product disqualification Originality/value: The use of thermovision system in processes of heating cakes evolution and also hot-rolling. These research enable a condition control of thermal furnace and hot-roll processes.

14

Thermo-mechanical fatigue conditions of power plant components

Okrajni J.

Journal of Achievements in Materials and Manufacturing Engineering

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2009

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Vol. 33, nr 1

53-61

EN

Purpose: The main purpose of this work is the description of the mechanical behaviour of power plant components working under mechanical and thermal loading that cause the thermo-mechanical fatigue fracture in selected areas of the component surfaces. Design/methodology/approach: The computer modelling has been used to describe the local stress-strain behaviour of the chosen component. Findings: The values of variable in time temperature strains and stresses in selected points of the power plant header were determined. The points were located at the edges of holes through which water steam is supplied and carried away, where under use conditions the presence of cracks can be observed. That stresses and mechanical strains caused by the influence of a non-uniform temperature field may be significantly higher in comparison with the stresses and strains caused by the pressure inside the analysed component. Tensile thermal stresses of high values are created especially under conditions of sudden cooling during unsteady work of a power unit. Research limitations/implications: The possibility of applying the durability criteria currently assumed in standards still requires justification and confirmation in laboratory and industrial conditions to be closer to the real components behaviour. In such situation the presented analysis is the part of the complex investigation method which main purpose is increasing accuracy of the TMF process description and thermo-mechanical life assessment. Practical implications: The calculations carried out may constitute a basis for developing a material test parameters which would bring closer the fatigue conditions appearing locally in the analysed components. The method of stress-strain behaviour analysis used in the paper could be useful in the practical cases when the real components mechanical behaviour would be analysed. Originality/value: The main value of this paper is the own method of the mechanical behaviour analysis of the power plant component. This method includes the temperature fields analysis taking into account the boundary conditions based on the operation parameter data and the thermoplastic material model. The material stress-strain behaviour has been treated as the local phenomenon, that could be modelled by FEM.

15

The influence of long-lasting annealing on microstructure of AlCu4Ni2Mg2 alloy

Wierzbińska M., Sieniawski J.

Journal of Achievements in Materials and Manufacturing Engineering

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2009

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Vol. 34, nr 2

122-129

EN

Purpose: of this paper was to determine the influence of long-term annealing at elevated temperature on the microstructure and mechanical properties of AlCu4Ni2Mg2 alloy. Design/methodology/approach: The microstructure was observed using optical light (LM), scanning (SEM) and transmission (TEM) microscopy. The mechanical properties were determined on a standard tensile test machine. Findings: It was found that after long time hold at elevated temperature (523 K) the degradation of microstructure of alloy was observed. The microstructural changes consist in increase of size of hardening phases precipitates (Č’-Al2Cu) and changing its shape. These phenomena cause decrease in the mechanical properties of the alloy. Research limitations/implications: In order to complete obtained results it is recommended to perform further investigations of behaviour of AlCu4Ni2Mg2 alloy in 573 K and 623 K corresponding to the maximum values of temperature at which structural elements of piston engines made of aluminium alloys operate. Practical implications: From a practical point of view it is important to realize, that however the Cu (about 4%) and Ni (about 2%) additions significantly influence increasing of mechanical properties of aluminium alloy, nevertheless don’t protect against the degradation of its microstructure and finally from decreasing of strength during machine elements operation. Originality/value: This work has provided essential data about microstructural changes of aluminium alloy proceeding during elements of piston engines operation.

16

Technological plasticity and structure in stainless steels during hot-working

Kuc D., Niewielski G.

Journal of Achievements in Materials and Manufacturing Engineering

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2009

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Vol. 32, nr 2

154-161

EN

Purpose: The high-temperature plastic deformation is coupled with dynamic processes of recovery influencing the structure and properties of alloys. One of crucial issues is finding the interdependence between the hot plastic deformation process parameters, the structure and properties. Design/methodology/approach: Hot plastic deformation was carried out using a torsion plastometer in the temperature range of 900-1150°C at a strain rate of 0.04-4 s-1. The plastometric investigations enabled the determination of the influence of deformation parameters on technological plasticity. Investigations of the samples’ structures were carried out using a light and electron microscope, by a thin film method. A quantitative analysis of structural changes was performed using the „MetIlo” image analysis programme. Findings: Results of the investigations have been provided referring to the influence of the hot plastic deformation process on the microstructure and the substructure as well as technological plasticity of steels of an austenitic, ferritic and ferritic-austenitic structure. Mathematical models were developed which link the deformation process parameters to the grain size obtained after the deformation as well as the mechanical properties determined in a torsion test. Practical implications: The research carried out enabled the understanding of the phenomena taking place during deformation and annealing of the investigated alloy. The results will constitute the basis for modelling the structural changes. Originality/value: The results obtained are vital for designing an effective thermo - mechanical processing technology for the investigated steels.

17

Structure and properties of forming austenitic X5CrNi18-9 stainless steel in a cold working

Ozgowicz W., Kurc A.

Journal of Achievements in Materials and Manufacturing Engineering

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2009

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Vol. 33, nr 1

19-26

EN

Purpose: The aim of the paper is to analyze the influence of the degree of rolling reduction on the structure forming and changes of mechanical properties in cold-rolled sheet-metals of austenitic X5CrNi18-9 stainless steel. Design/methodology/approach: The examinations contained metallographic observations of the structure on a light microscope and on the scanning electron microscope (SEM), researches of mechanical properties in a static tensile test and microhardness measurements made by Vickers’s method. The analysis of the phase composition was carried out on the basis of X-ray researches. In the qualitative X-ray analysis the comparative method was applied. Fractographic tests of the fracture after the decohesion of samples in a static tensile test at room temperature were executed in a SEM. Findings: It has been found that plastic deformation in a cold working of austenitic stainless steel type X5CrNi18-9 induced in its structure martensitic transformation . › .’. The occurrence of martensite phases .’ in the investigated steel structure has an essential meaning in manufacturing process of forming sheet-metals from austenitic steel. Research limitations/implications: The X-ray phase analysis in particular permitted to disclose and identify the main phases on the structure of the investigated steel after its deformation within the range from 10% to 70%. Moreover, the results of the X-ray quantitative analysis allowed to determine the proportional part of martensite phases .` in the structure of investigated steel in the examined range of cold plastic deformation. Practical implications: The analysis of the obtained results permits to state that the amount of martensite phases .` in the investigated steel structure increases with the degree of deformation in the cold rolling. Besides, a good correlation was found between changes of the structure and the effects of investigations of the mechanical properties. Originality/value: Good correlation between changes of the structure and the effects of investigations of the mechanical properties in the austenitic X5CrNi18-9 stainless steel was found.

18

Structure and properties of CuFe2 alloy

Rdzawski Z. M., Stobrawa J. P., Głuchowski W.

Journal of Achievements in Materials and Manufacturing Engineering

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2009

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Vol. 33, nr 1

7-18

EN

Purpose: The objective of this work was to investigate the changes taking place in the structure and properties of CuFe2 alloy caused by combined heat treatment and metal working. The objective of this paper was to describe phenomena related to the formation of functional properties CuFe2 strips, especially for obtaining hardness in 120-140 HV range and electrical conductivity above 35 MS/m. Design/methodology/approach: The investigated material consisted of two industrial melts of CuFe2. Systematic investigations of selected variants of heat treatment and plastic working operations were carried out. The investigations started with description of microstructure and properties in initial state, after quenching, after cold working, quenching and ageing, after quenching and ageing, after quenching, ageing and cold working and after cold working and annealing - omitting quenching and ageing process. Hardness test (HV) and electrical conductivity were determined on strip samples. Typical tension tests and metallographic investigations were also carried out. Findings: Structure and properties of industrial CuFe2 alloy differs significantly from the literature descriptions, especially after quenching process. It could be assumed, that the dissolved in a melting process alloy additives (in this case a part of dissolved iron) might be supersaturated, but some of them might be precipitated. This theory was confirmed by the results of investigation into mechanical properties, microstructure and electrical conductivity. Practical implications: The presented investigation results, besides their cognitive values, provide many useful information which might be implemented in a industrial practice. Originality/value: It was assumed that cold deformation with rolling reduction 70% and annealing at temperature 480oC for 12 hours provided possibilities to reach maximal electrical conductivity 37 MS/m and maximal hardness 136 HV.

19

Pitting corrosion in the wet section of the automotive exhaust systems

Hoffmann C., Gümpel P.

Journal of Achievements in Materials and Manufacturing Engineering

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2009

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Vol. 34, nr 2

115-121

EN

Purpose: In the rear section of the automotive exhaust systems condensates bearing appreciable chloride ion concentrations and often low pH-values together with particles of electrochemical active soot can lead to pronounced pitting corrosion on the inner surfaces. For selection of an appropriate material that can enable cost-effective construction, the corrosion resistance of different candidate grades has to be rated. Design/methodology/approach: The different types of occurring corrosion, both general attack and pitting corrosion demands a combination of evaluation methods of the corrosion attack: mass loss measurements and the measure of the average depth of a certain number of pits with an optical 3D-Measuring System MicroCAD were used. Findings: The two methods for the evaluation of the corrosion attack provide the same ranking of the materials. Both methods are complementary to each other and together they provide a noticeable differentiation between some of the investigated materials. Research limitations/implications: The average depth of the pits gives no information about the entire rate of the corrosion attack, about the total number of the pits and their depth. In the future, research with the same optical 3D-Measuring System MicroCAD and new software will be carried out. This will form a structured analysis of the entire pits for the quantification of the corrosion. Practical implications: A higher quantification of the pitting corrosion leads to a better rating of the different stainless steel grades for using them in the wet section of the automotive exhaust systems. Originality/value: The evaluation of the pitting corrosion by means of the new measurement methods with the optical 3D-Measuring System MicroCAD is more accurate, work fast and is an obligatory complement of the previous methods of evaluation of the pitting corrosion: mass loss and the depth of the deepest pit.

20

Phases morphology and distribution of the Al-Si-Cu alloy

Labisz K., Krupiński M., Dobrzański L. A.

Journal of Achievements in Materials and Manufacturing Engineering

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2009

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Vol. 37, nr 2

309-316

EN

Purpose: In this paper results of phase morphology investigation are presented of a newly developed Al-Si-Cu alloy. Such studies are of great interest for the metal casting industry, mainly the automotive industry, where improvement of cast elements quality is crucial for economic and quality reason and depends mainly on properly performed controlling process of the production parameters Design/methodology/approach: The basic assumptions of this work are realised with Universal Metallurgical Simulator and Analyzer. The solidification process itself is analysed using the UMSA device using the Derivative Thermo Analysis. Findings: During the investigation the formation of aluminium reach (á-Al) dendrites was revealed and also the occurrence of the á+â eutectic, the ternary eutectic á+Al2Cu+â, as well as iron and manganese containing phase was confirmed. This work shows that the thermal modification of the Al-Si-Cu can be quantitatively assessed by analysis of the microstructure evaluation as well as of the cooling curve thermal characteristics. Research limitations/implications: The investigations were performed using standard metallographic investigation as optical, scanning and transmission electron microscopy methods; also the EBSD phase identification method based on the kikuchi lines identification was used. The results in this paper are valuable only for the Al2Cu, Fe and Mg containing phases, and are not performed for the assessment of the Silicon Modification Level. Practical implications: As an effect of this study it will be possible to understand and to influence the mechanism of structure forming, refinement and nucleation. Also better understanding of the thermal characteristics will be provided to achieve a desirable phase morphology required for specific application of this material under production conditions. Originality/value: The originality of this work is based on applying of regulated cooling rate of aluminium alloy for structure and mechanical properties changes. In this work the dependence among the regulated cooling speed, chemical composition and structure of the investigated aluminium cast alloy on the basis of the thermo-analysis was presented.