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Fabrication of nano-structured materials by high-pressure sintering

100%

Czepelak M. , Staszewski M. , Wrona A. , Lis M. , Osadnik M.

2008

tom Vol. 30, nr 2

109-112

Purpose: The aim of this work was to fabricate nanocrystalline powders and high-density bulk materials using a sintering method with limited grain growth so as to maintain nanocrystalline structure of the materials also after sintering. Design/methodology/approach: The size of crystallites and physical properties of the obtained nanocrystalline powders and sinters made from these powders were examined. The studied materials were pure copper and the following powders: Cu+1%WC, Cu+3%WC, Cu+3%AlNi and AlNi. The technology for preparation of nano-structured powders was used, which included milling the powders in ball mills and their sintering in a pressing furnace. Findings: It was found that the objective of this work can be achieved provided that high-pressure sintering is used, in which the stages of compacting and sintering proceed simultaneously over a short period of time. Research limitations/implications: It is recommended to perform further studies aimed at checking the possibility of using the proposed method of nanomaterials fabrication in the case of the materials with other chemical composition. Practical implications: This work broadens possibilities of metal powder sintering technology by fabrication of bulk nanocrystalline materials. Originality/value: The results from his work shall be useful in determining conditions for fabrication of nanocrystalline or sub-microcrystalline materials by the sintering method.

Properties of rhenium-based master alloys prepared by powder metallurgy techniques

86%

Wrona A. , Staszewski M. , Czepelak M. , Woch M. , Kamińska M. , Osadnik M. , Kołacz D.

2010

tom Vol. 45, nr 2

95-101

Purpose: The aim of this work was to investigate an effect of phase composition, microstructure and selected properties of the rhenium-based alloys on the conditions of their preparation by mechanical alloying followed by pressure sintering. Design/methodology/approach: The structure and mechanical and physical properties of the Re-14.0% Ni, Re-13.7% Co and Re-9.1% Fe alloys prepared from pure metal powders by mechanical alloying in a planetary mill for 10 hours followed by sintering conducted for 1 hour at the temperature of 1150°C under the pressure of 600 MPa were investigated. Findings: The mechanical alloying results in partial dissolving of alloy components into each other, whereas their structure remains unchanged, and in a decrease in average density of powders and average diameter of their particles. As a result of sintering the alloy additives almost fully pass into rhenium-based solid solution. Density and hardness of the sinter compacts and homogeneity of alloying elements distribution were higher at longer times of mechanical alloying. Research limitations/implications: The obtained results provide complementary information on the possibility of obtaining high-melting alloys by mechanical alloying and on the rate of structural transformations taking place as a result of this process. Practical implications: The obtained materials can be used as master alloys for the production of contact materials and superalloys, providing higher homogeneity of the chemical composition and microstructure of the final products. Originality/value: A new method for preparation of rhenium-based alloys by means of mechanical alloying and powder metallurgy techniques has been successfully tested.