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1
Content available remote The iron-nickel-molybdenum (Fe-Ni-Mo) electrodeposited alloy on n-type silicon
100%
Fekih Z. , Ghellai N. , Sam S. , Chabanne-Sari N. , Gabouze N.
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tom Vol. 12, nr 1(31)
17-26
EN
In the present work, the electrodeposition of iron-nickel-molybdenum (Fe-Ni-Mo) alloy on n-type silicon (Si) is investigated. A voltamperometric study has been carried out. According to the composition of the solution and of its pH, the properties of final deposit have been investigated and analyzed by X-rays diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Under our conditions an amorphous FeNiMo alloy was formed. The morphology of deposited layer was strongly influenced by the polarization and the molybdenum dominance in the final chemical composition of the deposited film. Moreover, high percentages of molybdenum can be obtained from high molybdate concentrations and grain size increase with increasing Mo concentration. We also noticed that an absence of nickel was accomplished by applying more negative potential.
2
Content available remote Derivative thermo-analysis application to assess the cooling rate influence on the microstructure of Al-Si alloy cast
75%
Krupiński M. , Labisz K. , Dobrzański L. A. , Rdzawski Z. M.
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2010
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tom 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.
3
Content available remote Corrosion resistance of titanium in water solution of hydrochloric acid
75%
Lalik S. , Cebulski J. , Michalik R.
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2007
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tom Vol. 28, nr 6
349-352
EN
Purpose: Most of conducted research in the area of titanium corrosion are concentrated on determine the corrosion resistance in water solution of hydrochloric acid medium at high temperatures. Recognizing of corrosion mechanisms in liquid mediums can lead to obtain corrosion-proof material e.g. by applying passivation phenomenon. In this paper attention was paid to determine the corrosion resistance of titanium in corrosive medium of liquid hydrochloric acid with concentration of 6 and 10%. Research of material susceptibility to surface activation in the pipeline of corrosion processes are conducted. Design/methodology/approach: In the corrosion tests electrolyser, potentiostat "Solartron 1285" and computer with "CorrWare 2" software were used. Results of the research were worked out with "CorrView" software. The potentials values were determined in relation to normal hydrogen electrode (NEW). The temperature of the solutions was kept at 20 °C and 50 °C. The recording of potential/density of current-time curve was conducted for 300 s. Findings: The results of research, which were conducted in 6% and 10% HCl solution, show good corrosion resistance of titanium Gr1 in temperature 20 °C. Tested samples were characterized by susceptibility to surface self-passivation, with the exception of samples tested at temperature of 50 °C in HCl water solution. Damages of titanium passive surface during exploitation can lead to short-lived increase of corrosion rate in higher temperatures. Practical implications: Results of corrosion research allow to determine the durability of titanium in 6% and 10% water solution of hydrochloric acid at temperature 20 °C and 50 °C. Originality/value: The goal of this work was to on corrosion resistance of titanium in 6% and 10% HCl water solutions.
4
Content available remote Computer models of steam pipeline components in the evaluation of their local strength
63%
Okrajni J. , Essler W.
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2010
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tom 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.
5
Content available remote Micro-forming of Al-Si foil
63%
Haga T. , Inoue K. , Watari H.
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2010
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tom 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.
6
Content available remote The microstructure and properties of the bainitic cast steel for scissors crossovers
63%
Pacyna J. , Bała P. , Dobosz S. , Kokosza A. , Kąc S.
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2010
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tom 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.
7
Zastosowanie mikroanalizy rentgenowskiej w badaniach mikrostruktury stopów metali
63%
Warmuzek M.
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2000
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tom R. 3, nr 3
3-24
PL
W pracy przedstawiono przykłady zastosowania mikroanalizy rentgenowskiej EDS do badania mikrostruktury stopów metali. W syntetycznym skrócie przedstawiono podstawy zjawisk fizycznych będących źródłem informacji o lokalnym składzie chemicznym, możliwości analityczne metody, w tym jej dokładność, precyzję oraz granice wykrywalności oraz sposoby przygotowania próbek. Omówiono rozwiązania szeregu problemów związanych z identyfikacją składników strukturalnych i fazowych materiału z wykorzystaniem jakościowej i ilościowej mikroanalizy punktowej. Na przykładzie odlewniczego stopu Al-Si przedstawiono procedurę tworzenia "klucza do oznaczania faz" z wykorzystaniem barwnych obrazów mikrostruktury i punktowej mikroanalizy jakościowej. Zostały przedstawione przykłady weryfikacji wyników selektywnego trawienia składników mikrostrukturalnych oraz interpretacji obrazów struktury wielofazowej stopów aluminium i żelaza, uzyskanych za pomocą mikroskopu świetlnego oraz mikroskopu skaningowego, przy wykorzystywaniu wyników punktowej mikroanalizy ilościowej i jakościowej. Zaprezentowano także zastosowanie mikroanalizatora rentgenowskiego do tworzenia liniowych i powierzchniowych rozkładów stężeń wybranych pierwiastków w mikroobszarach stopu, wchodzących w skład stopu, w ujęciu jakościowym i ilościowym.
EN
The study gives examples of application of an X-ray EDS microanalysis in examinations of metals alloy microstructure. In brief analysis the fundamentals of some physical phenomena which provide information on the local chemical composition and analytical potentials of the method, including its accuracy, precision and limits of detectability as well as the technique of sample preparation, were revised. The solutions of numerous problems related with the identification of structural and phase constitutents in the examined materials due to the application of qualitative and quantitative point microanalysis were presented. Taking the cast Al-Si alloy as an example, the procedure of creating a "key for phase determination" with the help of colour microstructure images and qualitative point microanalysis was described. Further some examples of verification of the results of selective etching of microstructural constituents and interpretation of complex structure of aluminium and iron alloys, obtained by means of a light microscope and scanning microscope, utilising the results of qualitative and quantitative scanning microanalysis, were presented. The application of an X-ray microanalyser to study in both qualitative and quantitative approach the linear and surface distribution of the concentration of some selected elements present in microregions of the alloy composition was illustrated.
8
Content available remote Technological plasticity and structure in stainless steels during hot-working
63%
Kuc D. , Niewielski G.
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2009
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tom 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.
9
Content available remote Effect of heat treatment on tensile and fracture toughness properties of 6082 alloy
63%
Mrówka-Nowotnik G. , Sieniawski J. , Nowotnik A.
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2009
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tom Vol. 32, nr 2
162-170
EN
Purpose: The present study investigates the effect of heat treatment parameters (temperature and time) on the tensile properties and fracture toughness of 6082 aluminium alloy. Design/methodology/approach: Tensile strength - Rm, yield strength - Rp0.2 and elongation - A of the 6082 aluminium alloy were determined by uniaxial tensile test at room temperature. Furthermore, the aged alloy was tested in tension in order to evaluate its fracture toughness. Therefore, according to ASTM standard tests were performed on fatigue precracked compact tension (KIc) and sharp-notched specimens ( ) in both the longitudinal and transverse orientation with respect to the rolling direction. Findings: The results show that the microstructure, mechanical properties and fracture toughness changes during artificial aging due to the precipitation strengthening process. Practical implications: This paper is the part of previous authors’ investigations which results in modification of the heat treatment parameters that may lead to the most favorable mechanical properties and fracture toughness of 6082 alloy. Originality/value: Paper contains a broad spectrum of experimental data including uniaxial tensile test and fracture toughness investigation based on two various technique and as well as a new ideas concerning aging parameters and their effect on the mechanical properties and ductility of the 6082 alloy.
10
Content available remote Thermo-mechanical fatigue conditions of power plant components
63%
Okrajni J.
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2009
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tom 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.
11
Content available remote Structure and properties of CuFe2 alloy
63%
Rdzawski Z. M. , Stobrawa J. P. , Głuchowski W.
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2009
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tom 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.
12
Content available remote The influence of long-lasting annealing on microstructure of AlCu4Ni2Mg2 alloy
63%
Wierzbińska M. , Sieniawski J.
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2009
|
tom 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.
13
Content available remote Pitting corrosion in the wet section of the automotive exhaust systems
63%
Hoffmann C. , Gümpel P.
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2009
|
tom 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.
14
Content available remote Biomechanical characterization of the balloon-expandable slotted tube stents
63%
Pochrząst M. , Walke W. , Kaczmarek M.
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2009
|
tom Vol. 37, nr 2
340-347
EN
Purpose: The aim of the presented work was determination of the biomechanical characteristics of the vascular stent made of stainless steel (Cr-Ni-Mo) and Co-Cr-W-Ni alloy. Additionally, in order to compare obtained results, an experimental analysis of the stent made of stainless steel was carried out. Design/methodology/approach: In order to determine the strength characteristics of the analyzed stent the finite element method was applied. Geometrical model of the vascular stent, which was meshed with the use of the SOLID95 element, was worked out. Selection of the finite element was conditioned by large strains that occur during angioplastic procedure. The established boundary conditions imitated the phenomena during the balloon expansion in real conditions. Findings: The result of the analysis was determination of relationship between equivalent stresses and strains in the individual regions the stent in the function of the diameter’s change (d = 1.20 - 4.00 mm) caused by expanding pressure. Analysis of the obtained results indicates diverse distribution of stresses and strains in the stent depending on the applied biomaterial. Research limitations/implications: The obtained results of the biomechanical analysis of the coronary stent are valuable information for correct design of the geometry and mechanical properties of the applied metallic biomaterials. Strain analysis of the stent indicates that in order to limit a surface reactivity of the stent in blood environment, a deformable surface layer must be applied. Originality/value: Results of the numerical analysis indicate that mechanical properties of the metallic biomaterials used to manufacture the analyzed vascular stent were selected correctly. The correctness of the selection (mechanical properties of the metallic biomaterials) should be confirmed in in vitro tests realized with the use of the coronary angioplasty set.
15
Content available remote The effect of alloy powder morphology on microstructural evolution of hot worked P/M FeAl
63%
Śleboda T. , Doniec K.
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2007
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tom Vol. 28, nr 10
613-616
EN
Purpose: This paper presents the results of the research focused on the influence of both the starting FeAl alloy powder particle characteristics and the thermomechanical processing parameters on the microstructural evolution of these materials. Design/methodology/approach: Fully-dense FeAl alloy powder compacts were tested in compression on servohydraulic Gleeble testing machine, at the temperature range of 700*C to 1100*C, and at strain rates of 0.1 s -1 and 10 s -1. After processing, the microstructure of each deformed specimen was examined using optical microscopy. Findings: Considerable strain rate sensitivity of the investigated alloy was observed, especially with reference to microstructural development. The use of alloy powders in thermomechanical processing of FeAl alloys can substantially enhance the possibility to control both the microstructure and mechanical behavior of these alloys. Research limitations/implications: The influence of starting FeAl alloy powder particle morphology and processing strain rate on the microstructural evolution of investigated alloy was discussed. Practical implications: The results of this research could be directly employed in the design of deformation schedules for the industrial processing of FeAl alloys. Originality/value: FeAl alloy powder morphology influences the thermomechanical processing of P/M FeAl alloys, what was proved in this paper.
16
Content available remote Influence of bone union electrostimulation on corrosion of bone stabilizer in rabbits
51%
Szewczenko J.
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2007
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tom Vol. 28, nr 5
277-280
EN
Purpose: The aim of the work was determination of influence of the selected methods and parameters of bone union electrostimulation on corrosion of stainless steel implants coated with passive and passive-carbon layer. Design/methodology/approach: The semi-invasive and capacitively coupled electrical field methods of electrostimulation (without constant component) in rabbits were applied. The influence of electrostimulation on corrosion of implants was evaluated on the basis of the mass measurements and surface observations. Findings: On the basis of the research no corrosion on the implants stabilizing the bone fracture was observed. Research limitations/implications: Lack of visible and measurable corrosion requires the change of the methodology. Further research should be focused on the amount of metallic ions dissolved from the implants. Furthermore, it should be emphasized that the absence of corrosion of the electrostimulated implants is only one of many criteria describing the usefulness of electrostimulation parameters. The basic criterion is the biological effect obtained as the result of the electrostimulation. Practical implications: The obtained results are the basis for selection of methods and current parameters of the bone union electrostimulation in further clinical research. In case of positive results, the bone union electrostimulation with the use of implants coated with the passive and passive-carbon layers would be valuable method in treatment of pathological bone fractures. Originality/value: The paper is a continuation of the research on determining safe parameters of bone union electrostimulation of implants coated with the passive and passive-carbon layers.
17
Content available remote Structure and properties of forming austenitic X5CrNi18-9 stainless steel in a cold working
51%
Ozgowicz W. , Kurc A.
|
2009
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tom 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
Content available remote Achieving combined high strength and high conductivity in re-processed Cu-Cr alloy
51%
Olofinjanaa A. O. , Tan K. S.
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2009
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tom Vol. 35, nr 1
14-20
EN
achieve the optimum combination for strength and conductivity in copper based alloys. However, precipitation strengthened Cu- alloys are limited to very dilute concentration thereby limiting the volume proportion hardening precipitates. In this work, we report the investigation of the reprocessing of higher Cr concentration Cu- based alloys via rapid solidification. Design/methodology/approach: The ingot alloys with Cr content up to 10 wt.% were prepared via semi-chilling of small rods before been cast into ribbon using chill block melt spinner. Thermal aging studies followed by conductivity and microhardness tests were performed to follow the HSHC properties. Findings: It is found that the rapid solidification in the as-cast ribbon imposed combined solution extension and ultra-refinement of Cr rich phases. X-ray diffraction evidences suggest that the solid solution extension was up to 6wt%Cr. Lattice parameters determined confirmed the many folds extension of solid solution of Cr in Cu. Thermal aging studies of the cast ribbons indicated that peak aging treatments occurred in about twenty minutes. Peak aged hardness ranged from about 200 to well over 300Hv. The maximum peak aged hardness of 380Hv was obtained for alloy containing 6wt.%Cr but with conductivity of about 50%IACS. The best combined strength/conductivity was obtained for 4wt.%Cr alloy with hardness of 350HV and conductivity of 80% IACS. The high strengths observed are attributed to the increased volume proportion of semi-coherent Cr rich nano-sized precipitates that evolved from the supersaturated solid solution of Cu-Cr that was achieved from the high cooling rates imposed by the ribbon casting process Research limitations/implications: The rapid overaging of the high Cr concentration Cu-Cr alloy is still a cause for concern in optimising the process for reaching peak HSHC properties. It is still important to investigate a microstructural design to slow or severely restrict the overaging process. Originality/value: The optimum HSHC property reported here is a rare combination of high strength (>350Hv ~ 900MPa) and conductivity (50 – 80% IACS) found in metallic alloys.
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