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1

In situ-formed, low-cost, Al-Si nanocomposite materials

Guba P., Gesing A.J., Sokolowski J., Conle A., Sobiesiak A., Das S. K.

Journal of Achievements in Materials and Manufacturing Engineering

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2017

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Vol. 84, nr 1

5--22

EN

Aluminum-Silicon (Al-Si) alloys are the “bread-and-butter” of the aluminum foundry industry being cast at an annual rate of over 2 million tonnes/year in North America for use mainly in transportation. Coarse microstructure of these alloys limits their specific mechanical properties and consequently their potential for vehicle lightweighting. Purpose: We report on a new family of cast Al-Si alloys producing in-situ formed nanocomposites of up to 25 vol.% ultrafine equiaxed silicon particles in Al alloy matrix which can be ductile, or reinforced by nano-scale spinodal constituents. Design/methodology/approach: The hypereutectic Al-Si-X alloy (A390) was melted, solidified and cooled on the novel High Pressure Die Casting Universal Metallurgical Simulator and Analyser Technology Platform (HPDC UMSA) at specific process parameters. The HPDC cast samples consecutively were solution treated and artificially aged to spheroidize the Si and to dissolve the intermetallics in Al(SS) and to re-precipitate them in the solid state as nano-sized spinodal structures. The heat treatment was performed using the High Temperature UMSA Technology Platform. Findings: The nano scale structure of these new materials gives them significantly improved strength, hardness, and wear resistance while retaining adequate toughness and ductility for applications in the transportation applications. Research limitations/implications: Desired composite nanostructures have been produced and characterized in-situ in small laboratory test samples. Practical implications: These new materials can be produced by conventional casting technologies such as continuous strip casting, or high-pressure die-casting from conventional low-cost Al-Si melts. Originality/value: These materials can be produced with a significantly higher volume fraction of ultrafine Si dispersoids than has been done to date in in-situ formed materials, while retaining and improving the density-specific mechanical properties.

2

Effect of combinative cooled addition of strontium and aluminium on mechanical properties AlSi12 alloy

Lipiński T.

Journal of Achievements in Materials and Manufacturing Engineering

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2017

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Vol. 83, nr 1

5--11

EN

Purpose: The study was to determine the mechanical properties of hypo-eutectic silumin AlSi12 modified with Sr or Al-Sr alloy slow or fast cooled and in the form of a strip or powder. Design/methodology/approach: The experiment performed on EN AB-AlSi12 hypoeutectic alloy. Aluminium and strontium was melted and next fast cooled to room temperature or cooled on a metal plate at rates about 200°C/s. This enabled to produce a different components, which were powdered immediately before adding to the alloy or used as a strip. The scope of this paper was to verify the cooling effect of Sr-Al modifiers and its form (powder or strip) on the microstructure and mechanical properties the AlSi12 alloy. Findings: The use of fast cooled Al-Sr alloy in the modification process and/or powdered alloy contributed to a further increase mechanical properties AlSi12 alloy. Research limitations/implications: The modification alloys with fast cooled powdered modifier are attractive for future research. Practical implications: Widely presented books and research papers on the silumin treatment give not a lot of contents on the effect treatment fast cooled alloy in the form of a strip or powder. Originality/value: The original value of the paper is comparison Sr and Al-Sr alloy modifiers slow and fast cooled and used as a powder or strip.

3

Phase transformations in the precipitation hardened cast steel

Pacyna J., Dziurka R., Grudzień M.

Archives of Materials Science and Engineering

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2015

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Vol. 73, nr 2

62--68

EN

Purpose: The microstructure of the new ledeburitic, tool cast steel of the precipitation hardened matrix was designed. The concept of this microstructure was based on the microstructure of the steel-bonded carbides [1,2], in which a skeleton is built of sintered carbides. This skeleton is produced by the powder metallurgy methods and then filled with melted steel of the selected chemical composition. Design/methodology/approach: The new cast steel of the structure analogous to the steel-bonded carbides was conventionally melted in a furnace, however with omitting pressing and sintering operations of the powder metallurgy. The carbides skeleton in the new cast steel is formed by carbides of the MC type forming jointly ledeburite and its matrix constitutes steel hardened by precipitates of intermetallic compounds. This new material will be destined for tools of a moderate hardness (approximately 40 HRC), high abrasion resistance and high strength. Findings: Utilising hard carbides forming by elements of VB group of the Mendeleev’s table it is possible to design the tool material similar to the steel-bonded carbide of the selected matrix composition and primary carbides of MC type. Research limitations/implications: The chemical composition the matrix of designed material decides on its hardness and strength, the MC type carbides decide on the abrasion resistance and if they occur in the eutectic form they decide on a rather low fracture toughness. Therefore efforts should be undertaken to have non-ledeburitic materials. Practical implications: As a result of these investigations a new precipitation hardened cast steel have been worked out and a possibility of its industry applied was shown. Originality/value: The results of investigations of phase transformations in the new cast steel at its heating and cooling from the austenite range, are presented in the hereby paper.

4

The influence of production method on oxidation resistance of the aluminide coatings obtained on IN 100 alloy

Pytel M., Góral M., Maliniak M.

Archives of Materials Science and Engineering

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2012

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Vol. 53, nr 2

102-108

EN

Purpose: The comparison of three deposition of coatings method. Design/methodology/approach: The diffusion aluminide coatings were deposited using the pack cementation, out of pack and CVD method. Findings: The authors present in the article the results on influence of the method of manufacturing the aluminide coatings on their microstructure and oxidation resistance. Research limitations/implications: The thickness analysis and the chemical composition analysis with a use of light microscopy, scanning electron microscopy and EDS analysis were performed. Practical implications: This process can be used in aerospace industry to form oxidation resistant coatings. Originality/value: It has been proven, that the coating obtained with CVD method, despite its small thickness, was characterized by the best cyclic oxidation resistance.

5

Structure and stresses in high dimension brazed joints of cermets and steel

Nowak J.

Archives of Materials Science and Engineering

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2012

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Vol. 53, nr 2

69-76

EN

Purpose: of this paper is description of stresses in brazing joints of different physical and mechanical properties and evaluation of microstructure and mechanical properties of large dimensional vacuum brazed joints of WC–Co (ISO K05), Fe-TiC sinter plates (Ferro–Titanit Nicro 128) and precipitation hardened stainless steel of 14-5 PH (X5CrNiMoCuNb14-5) using copper as the brazing filler metal. Design/methodology/approach: Microscopic examinations with the use of scanning electron microscope were performed to establish microstructure of the joint. Shear strength Rt and tensile strength Rm of the joints have been defined. Findings: It have been state, that the basic factors decreasing strength of the joint, which can occur during vacuum brazing of the WC-Co, Fe-TiC sinters - Cu brazing filler metal - 14-5 PH steel joints are diffusive processes leading to exchange of the cermets and brazing filler metal elements. They can have an unfavourable influence on ductility and quality of the joint.. Research limitations/implications: Results of numerical calculations of three-dimensional models of cermets and steel brazed joints stresses are presented. Particular attention was paid to stresses occurring in joints of large brazing surfaces. It was shown that joints microstructure and mechanical properties depend on chemical composition filler and parent materials, diffusion process during brazing, leading of the cermets and filler metal components replacement as well as joint gap thickness. The thickness of the joints and parent materials have an essential influence on the value of the local stress. Practical implications: As a result of conducted experiments criteria for generating high dimension coatings of cermets plates brazed to steel. The PM Fe-TiC and PM WC - Co composite plates vacuum-brazed to steel as cutting coatings have been worked out and applied in industry. Originality/value: An original value of the paper is to prove the tendency of concentration gradients of alloying components and intermetallic phases creation and factors reducing stresses which may occur during vacuum brazing of The PM Fe-TiC and PM WC-Co and corrosion resistance steel.

6

Microstructure and kinetic growth of aluminide coatings deposited by the CVD method on Re 80 superalloy

Nowotnik A., Sieniawski J., Góral M., Pytel M., Dychton K.

Archives of Materials Science and Engineering

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2012

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Vol. 55, nr 1

22-28

EN

Purpose: The preliminary results of research on forming the aluminide coatings using CVD method were presented in the article. Design/methodology/approach: The coatings were obtained in low activity process on the surface of Rene 80 superalloy. The microstructure analysis and chemical composition analysis were performed applying different values of aluminizing process parameters. Findings: The authors present in the article the results of oxidation resistance analysis of aluminide coatings which were obtained on the surface of Rene 80 superalloy using various techniques. Research limitations/implications: The research results revealed the possibility of obtaining coatings by low activity aluminizing. Practical implications: This process can be used in aerospace industry to form oxidation resistant coatings. Originality/value: It was shown that the coating created during the CVD process was characterized by a good oxidation resistance at the temperature of 1100°C.

7

Light and electron microscope investigations of cast Zn-Al alloys

Krupińska B., Rdzawski Z., Labisz K.

Archives of Materials Science and Engineering

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2012

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Vol. 55, nr 1

29-36

EN

Purpose: The aim of this work is to determine the influence of alloy modification on the crystallisation kinetics and microstructure of the cast zinc alloy. This research work presents also the investigation results of derivative thermoanalysis performed using the UMSA device. The material used for investigation was the ZnAl8Cu1 alloy. Design/methodology/approach: approach The UMSA (Universal Metallurgical Simulator and Analyser) device allows it to determine the specific points of the solidifying alloy, including: Influence of the chemical concentrations of the modifiers, alloying additives, parameters of the melting process, influence of the cooling rate on the crystallization of phases and eutectics of the investigated alloys. Cooling rate influences the microstructure and properties of the investigated zinc cast alloys. For phase determination electron diffraction investigations were performed carried out on the transmission electron microscope. Findings: Change of the crystallization kinetics allows it to produce materials with improved properties, which are obtained by: microstructure refinement, reduction or elimination of segregation. Research limitations/implications: The material was examined metallographically and analysed 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: Investigations concerning the development of optimal chemical composition and production method of zinc-aluminium alloys with selected rare earth metals with improved properties compared to elements made of alloys with appliance of traditional methods, will contribute to a better understanding of the mechanisms influencing the improvement of functional properties of the new.

8

Influence of turbine blade geometry on thickness of TBCs deposited by VPA and PS-PVD methods

Góral M, Sieniawski J., Pytel M., Masłyk M.

Archives of Materials Science and Engineering

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2012

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Vol. 54, nr 1

22-28

EN

Purpose: The authors presented in the article the influence of the jet engine turbine blade profile on the thickness and microstructure of thermal barrier coatings. Design/methodology/approach: The assessment of model blade made of ZS6K alloy used in the first stage of the turbine engine was performed. The diffusion aluminide coating as well as the thermal barrier coating were deposited on the blade surface with a use of the out of pack method. The zirconia stabilized by yttrium oxide coating was deposited by PS-PVD method The research was performed with a use of light- and scanning microscopy. Findings: It has been proven, that the thickest coating was found on the leading edge and trailing edge of the blade. In those places the coating thickness was approx. 20-30% larger than in the other areas on turbine blade. Research limitations/implications: The research was performed with a use of light- and scanning microscopy. Practical implications: The obtained results indicate that it is possible to create the thermal barrier coating by PS-PVD process on the first stage turbine blades of the aircraft engine. It indicates the possibility of application of this process in the industrial practice. Originality/value: The new method for TBC coating production were used.

9

Antibacterial properties of copper and its alloys

Konieczny J., Rdzawski Z.

Archives of Materials Science and Engineering

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2012

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Vol. 56, nr 2

53--60

EN

Purpose: The goal of the work is analysis of the knowledge extent on the bactericidal activity of copper and its alloys. Design/methodology/approach: Analysis of publications on the antibacterial properties of copper in the engineering and medical journals, taking also into account publications on the earliest documented employment of copper as the bactericide or medicine. Findings: Analysis of the investigation results presented in more than 350 scientific publications and reports worked out under commission from the Ministry of Health, including 312 scientific publications from the years 1892-1973, indicate to the antimicrobial action of copper and its alloys, which killing bacteria and viruses slows down growth of the microorganisms, and especially of: cobacillus, Legionella pneumophila, Salmonella, Staphylococcus aureus, poliovirus. Research limitations/implications: Application of the acquired research results in hospitals, outpatients’ clinics, and other public medical centres, will make it possible to reduce morbidity resulting from infections, especially of patients after serious medical treatment, operations, or after the complex antibiotic cure which has led them to decline of immunity. Practical implications: Reduction of health care costs is possible in every country by implementation of the acquired investigation results, as a consequence of the decreased treatment costs, by shortening the patients’ stay in a hospital. According to the assessment of the Department of Health of the United Kingdom these savings total to 1 billion pounds a year. Originality/value: Implementation of the analysis of results of investigations on the bactericidal activity of copper and copper based alloys will add to the increase of the patients’ safety level in the public medical centres.

10

Non-metallic inclusions in high manganese austenitic alloys

Grajcar A., Galisz U., Bulkowski L.

Archives of Materials Science and Engineering

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2011

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Vol. 50, nr 1

21-30

EN

Purpose: The aim of the paper is to identify the type, fraction and chemical composition of non-metallic inclusions modified by rare-earth elements in an advanced group of high-manganese austenitic C-Mn-Si-Al-type steels with Nb and Ti microadditions. Design/methodology/approach: The heats of 3 high-Mn steels of a various content of Si, Al and Ti were melted in a vacuum induction furnace and a modification of non-metallic inclusions was carried out by the mischmetal in the amount of 0.87 g or 1.74 g per 1 kg of steel. Evaluation of the metallurgical purity of steels with non-metallic inclusions was done basing on determination their fraction, type, size and morphology. Stereological parameters of the inclusions were assessed by the use of automatic image analyzer cooperating with light microscope. EDS method was used to assess the chemical composition of non-metallic inclusions. Findings: It was found that the steels are characterized by high metallurgical purity connected to low concentrations of phosphorus and gases at a slightly higher sulphur content, introduced to a melt together with electrolytic manganese. The steels contain fine sulfide inclusions with a mean size from 21 to 25 ěm2 in a majority and their fraction equals from 0.047 to 0.09%, depending on sulphur content. MnS, carbonitrides of the (Ti,Nb)(C,N) type and complex carbosulfides containing Mn, Ti and Nb were identified in steels. The beneficial influence in decreasing a fraction of non-metallic inclusions and their susceptibility to elongate in a rolling direction has a higher addition of mischmetal and titanium microaddition. A modification of the chemical composition of non-metallic inclusions by Ce, La and Nd proceeds in an external zone of inclusions. Research limitations/implications: Further investigations relating the type and morphology of non-metallic inclusions to mechanical properties of sheets at various sections according to the rolling direction are needed. Practical implications: The knowledge of the type and morphology of non-metallic inclusions forming in high-Mn alloys and the effectiveness of their modification has a significant meaning for metallurgical and steel making technologies. Originality/value: A problem of the identification of non-metallic inclusions modified by REE and titanium is a new topic in studies on the metallurgical purity of advanced high-strength high-manganese steels.

11

Microstructure and selected properties of Mn-Al duplex steels

Niewielski G., Kuc D., Cebulski J., Lalik S.

Archives of Materials Science and Engineering

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2011

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Vol. 47, nr 1

11-18

EN

Purpose: Automotive industry constantly demands high-strength steels which are characterized by the energy absorption possibilities during a collision. Such materials may, in the future, replace the currently used conventional steels. The groups of steels which meet these criteria are the austenitic steels and austenitic-ferritic steels with high manganese content (15-30%) and high aluminium content (1-6%). Design/methodology/approach: The influence of the chemical composition on the mechanical properties of steel with high carbon, manganese and aluminium concentration was analysed in this paper. Moreover, the susceptibility of those steels to hot deformation was assessed in plastometric tests. Findings: The conducted research enabled the optimisation of the chemical composition of duplex steels and manufacture of steel with favourable relation of strength to ductility. Practical implications: The obtained steel is characterised by beneficial properties which outbalance the austenitic steels type TWIP and may be applied in vehicle construction on elements connected with safety. Originality/value: The achieved results will be used to develop a technology of thermomechanical treatment of duplex steels.

12

Evolution of secondary phases in GX12CrMoVNbN9-1 cast steel after heat treatment

Golański G.

Archives of Materials Science and Engineering

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2011

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Vol. 48, nr 1

12-18

EN

The paper deals with the investigation of secondary phases evolution during quenching, quenching and tempering in the high – chromium martensitic GX12CrMoVNbN9-1 (GP91) cast steel. It also includes the analysis of evolution of secondary phases in the as - cast condition and after stress relief annealing at the temperature of 750°C of the tempered GP91 cast steel.

13

Changes of microstructure in CuNi25 alloy deformed at elevated temperature

Sakiewicz P., Nowosielski R., Griner S., Babilas R.

Archives of Materials Science and Engineering

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2011

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Vol. 50, nr 2

98-109

EN

Purpose: The aim of this paper was to present behaviour of CuNi25 alloy during elevated temperature tensile tests and describe changes of microstructure of material after deformation at the range of the Ductility Reduced Area (DRA) in which the phenomenon of Ductility Minimum Temperature (DMT) is situated. Design/methodology/approach: Numerous techniques were used to characterize properties of material: high temperature tensile tests, transmission electron microscopy (TEM), HRTEM, FFT. Findings: During the experimental studies the course of elongation and reduction of area curves has been determined. Morphology of material after deformation at elevated temperature was analysed. Research limitations/implications: Further studies should be undertaken in order to correlate effects, processes and mechanism existing and superimpose in material in range of Ductility Minimum Temperature phenomenon, it should help us understand high temperature properties of mentioned material. Practical implications: Knowledge about material properties during high temperature deformation leads to selection of the appropriate production parameters. Misapplication of parameters leads to multiplication of costs and often destruction of material during production or operating. Correct selection of technical and economical parameters of material production processes gives us supremacy in economic and technological competition. Originality/value: Investigations of this CuNi25 alloy complete knowledge about mechanical properties and help us develop correct parameters for more effective technologies for material production.

14

Properties of sandwich metals joined by explosive cladding method

Čížek L., Ostroushko D., Szulc Z., Molak R., Praźmowski M.

Archives of Materials Science and Engineering

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2010

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Vol. 43, nr 1

21-29

EN

Purpose: Paper presents results of investigations with two layers explosively formed sandwich composite consisting of different composition joint which requires very often knowledge of structure and mechanical properties. These properties are connected with microstructure that is influenced by technological factors under cladding. Design/methodology/approach: The sample bars were prepared from explosively formed sandwich composite near the join area. The methods of the light microscopy and the hardness and tensile test for evaluation of quality of joined sandwich metals were used. Investigations by a new fatigue method in the case sandwich composite steel CrNi(18/10) + Ti were completed. Findings: Measurement of micro-hardness in the zone of the joint a deformation of materials shows an increase value of that. Detailed metallographic observation detected in proximity of the joints an occurrence of structural non-homogeneities. Steel and titanium interface surfaces are corrugated. New fatigue method in the case sandwich composite steel CrNi(18/10) + Ti were verified. Research limitations/implications: Knowledge of microstructure characteristics will be extended by the method of SEM, including micro-analysis of individual structural components and surface analysis. Influence of experiment conditions on results of fatigue test must be more elaborated in future. Practical implications: The results may be utilized for a relation between structure and properties of the investigated materials in process of manufacturing. Originality/value: These results contribute to complex evaluation of properties explosively formed sandwich composite namely for explanation of structure developed new sandwich composites. The results of this paper are determined for research workers deal by development new exploitations of new sandwich composites.

15

Influence of chemical composition variation and heat treatment on microstructure and mechanical properties of 6xxx alloys

Mrówka-Nowotnik G.

Archives of Materials Science and Engineering

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2010

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Vol. 46, nr 2

98-107

EN

Purpose: The main task of this work was to study the effect a the precipitation hardening on the microstructure and mechanical properties of 6061, 6063 and 6082 aluminium alloys. Design/methodology/approach: In this paper differential scanning calorimetry (DSC) and hardness measurements have been utilized to study the effect of a precipitation hardening on the mechanical properties in 6xxx aluminium alloys. The mechanical (Rm and Rp0.2) and plastic (A, Z) properties of the examined alloys were evaluated by uniaxial tensile test at room temperature. The microstructure was observed using optical microscope - Nikon 300, scanning electron microscope HITACHI S-3400 (SEM) in a conventional back-scattered electron mode. Findings: The results show that the microstructure and mechanical properties changes during artificial aging due a the precipitation strengthening process. Therefore, the parameters (time and aging temperature) of precipitation strengthening process that may lead to the most favourable mechanical properties of 6061, 6063 and 6082 alloys were determined. Practical implications: This paper is the part of previous author's investigations which results in modification of the heat treatment parameters that may lead to the most favorable mechanical properties of 6xxx alloys. Originality/value: The paper has provided essential data about influence chemical composition and aging parameters on the microstructure and mechanical properties of 6061, 6063 and 6082 alloys.

16

Effect of the heat treatment on the structure and properties of GX12CrMoVNbN9-1 cast steel

Golański G.

Archives of Materials Science and Engineering

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2010

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Vol. 46, nr 2

88-97

EN

Purpose: The paper presents the influence of heat treatment parameters (austenitization and tempering temperature) on the microstructure and mechanical properties of high - chromium martensitic GX12CrMoVNbN9-1 (GP91) cast steel. Moreover, the influence of stress relief annealing at the temperatures of 730 and 750oC on microstructure and properties has been investigated. Design/methodology/approach: Microstructure of the cast steel was characterized using optical metallography and transmission electron microscopy. Identification of precipitates was made by means of thin foils and extraction carbon replicas. The size of precipitations was determined by Image Pro Plus software. Moreover, the mechanical properties (static tension, hardness and impact energy) have been tested. Findings: What has been determined is the influence of heat treatment parameters on microstructure and mechanical properties of GP91 cast steel. Heat treatment (hardening and high-temperature tempering) of GP91 cast steel allowed to obtain a fine-grained microstructure of high-tempered martensite with numerous precipitates whose properties met the standard requirements, regardless of the heat treatment parameters. Research limitations/implications: It is necessary to continue the research to determine description of the microstructure after different heat treatment parameters. Practical implications: Optimization of the heat treatment parameters from the aspect of using the investigated cast steel for long-term operation in power units designed for working at the so-called supercritical parameters. Originality/value: The relationship between the heat treatment parameters (austenitization and tempering temperatures) and mechanical properties of high - chromium martensitic GX12CrMoVNbN9-1 (GP91) cast steel was specified. Moreover, the influence of the stress relief annealing parameters on microstructure and properties has been shown.

17

ECAP methods application on selected non-ferrous metals and alloys

Rusz S., Čížek L., Dobrzański L., Tylšar S., Kedroň J.

Archives of Materials Science and Engineering

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2010

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Vol. 43, nr 2

69-76

EN

Purpose: Paper presents results of investigations mechanical properties and microstructure samples selected nonferrous metals after ECAP. These properties and microstructure are influenced by technological factors during application ECAP method. Design/methodology/approach: The sample bars were plastically deformed during the ECAP process. The methods of the light microscopy and the hardness test for evaluation of mechanical properties and microstructure were used. Findings: Measurement of micro-hardness shows an increase value after application higher number of passes in agreement with ultra high fine grain occurrence. The method determines the dependencies of force on the route during the ECAP process. Research limitations/implications: Achieved hardness and microstructure characteristics will be determined by new research. Practical implications: The results may be utilized for a relation between structure and properties of the investigated materials in future process of manufacturing. Originality/value: These results contribute to complex evaluation of properties new nonferrous metals after application ECAP method. The results of this paper are determined for research workers deal by the process severe plastic deformation.

18

Cooling rate influence on microstructure of the Zn-Al cast alloy

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

Archives of Materials Science and Engineering

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2010

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Vol. 43, nr 1

13-20

EN

Purpose: In this work was presented the cooling rate influence on microstructure of the Zn-Al cast alloy. This research work presents also the investigation results of derivative thermoanalysis performed using the UMSA device. The material used for investigation was the ZnAl4Cu1 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: The material was examined metallographically and 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 conditions.

19

The structural study of Ti-Si-C alloys produced by mechanical alloying method

Pilarczyk W., Nowosielski R., Pilarczyk A.

Archives of Materials Science and Engineering

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2009

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Vol. 38, nr 2

78-84

EN

Purpose: The aim of this paper is to determine the influence of the alloying time and composition on the structure of Ti-Si-C alloy. Design/methodology/approach: The powders of the Ti-Si-C alloys were obtained by mechanical alloying method in a planetary Fritsh Pulverisette 5 mill under inert argon atmosphere. In order to investigate the structure scanning electron microscopy, transmission electron microscopy and optical microscopy were used. Phase transformations during mechanical alloying process were determined by means of diffractometer. The distribution of particle sizes of powder materials was determined by a laser analyser. Findings: The application of the mechanical alloying method gives opportunity to produce nanocrystalline and amorphous phase. The laboratory test show that, by using this method, one can produce alloys with intentional chemical constitution and desirable structure. Research limitations/implications: : The powder metallurgy techniques make it possible to obtain Ti-Si-C massive materials by means of milling, followed by compacting and sintering. All of the experiments presented in this article are made on a laboratory scale. Further investigations should be concentrated on the developing of powder sintering method. Originality/value: This scientific research will be helpful for the composition plan for higher Ti3SiC2 content of powder synthesis. The synthesis of Ti-Si-C powder gives opportunity for the development of dispersion-strengthened alloys. The Ti-Si-C alloys have been considered to be potentially important for high temperature applications as either a structural or functional material.

20

The investigations of hot-deformability and structure of high-temperature Fe-Ni alloy

Ducki K., Kuc D.

Archives of Materials Science and Engineering

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2009

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Vol. 35, nr 2

83-90

EN

Purpose: This study describes the influence of initial austenite grain size and parameters of hot plastic deformation on the deformability and structure of high-temperature Fe-Ni austenitic alloy of A-286 type. Design/methodology/approach: The hot deformation characteristics of the alloy were investigated by hot torsion tests using torsion plastometer. The tests were executed at constant strain rates of 0.1 and 1.0 s-1, at a testing temperature in the range from 900 to 1150 °C. The structural inspections were performed on microsections taken from plastometric samples after so called "freezing". Findings: Plastic properties of the alloy were characterized by the worked out flow curves and the temperature relationships of flow stress and the strain limit. The relationship between the peak stress (σpp) and the Zoner-Hollomon parameter (Z) were described by power function. Activation energy for hot working (Q) was assessed for the alloy after two variants of previous heating. The examinations performed, focusing on the influence of hot working parameters on the structure of austenitic alloy, revealed subsequently occurring processes of dynamic recovery, recrystallization and repolygonization. Practical implications: Characteristics of the alloy plastic properties during hot deformation depend considerably on the initial soaking temperature and hot deformation parameters. Optimum values of yield stress and strain limit were obtained for the alloy after its initial soaking at 1100 °C/2h and strain rate of 0.1 s-¹ in the temperature range of 1050-950 °C. Originality/value: An increase of the alloy deformation temperature led to a growth of the size of subgrains with a simultaneous decrease of their internal dislocation density. The influence of the strain rate of the alloy on the size of subgrains and dislocation density is complex by nature and depends on the initial size of the austenite grains and on the mechanism of the dynamic recrystallization process.