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Compressive Creep Tests of An Aluminium Powder Composite Reinforced by Ceramic Particles
Dvořák, Jiří ; Král, Petr ; Balog, M. ; Simančík, F. ; Sklenička, Václav
The aim of this work is to study of a composite mixture of aluminium powders, to analyze of composite microstructure and mostly to describe the creep behaviour of composite in compression. The experimental material was based on Al powder matrix (Al 99%) about the particle size of less than 200 µm. This powder was mixtured with silicon carbide particles (SiC) having the size about 10 µm. The Al composite powder was prepared via conventional direct hot-extrusion (DE) at temperature 450°C. The microstructural investigations were performed using OM and SEM. It was found that DE process exhibits some breaking of carbide particles to size of range from 0.5 to 5 µm. Creep tests in compression were conducted at temperatures 423 -623 K and at applied stresses in the range from 60 to 100 MPa. Consequently, for an evaluation of controlling creep mechanisms an activation energy of creep and the stress exponent of the creep rate were determined.
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INFLUENCE OF ECAP TECHNIQUE ON CREEP BEHAVIOUR OF POWDER ALUMINIUM PROCESSED BY DIRECT EXTRUSION
Dvořák, Jiří ; Král, Petr ; Balog, M. ; Simančík, F. ; Sklenička, Václav
The Al powder was prepared by cold isostatic pressing at the pressure of 200 MPa. The granulometric powder fraction of a particle size less than 400 µm was compacted via conventional direct hot-extrusion (DE) at temperature 450°C. This material was then subjected to ECAP technique up to 4 passes. The microstructural investigations were performed using OM and SEM equipped with an EBSD unit. Creep tests in tension were conducted at temperature of 473 K and at applied stresses in the range from 30 to 60 MPa. Some creep tests in compression were performed on material just after DE. The paper presents results of study of microstructure and creep behaviour of aluminium powder before and after ECAP. It was found that ECAP method does not lead to an additional marked refinement of grain size. However, in dependence on number of ECAP passes ECAP method markedly influences creep behaviour due to development of high-angle grain boundaries during ECAP process.
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Microstructure and mechanical properties of powder aluminium prepared by severe plastic deformation
Dvořák, Jiří ; Král, Petr ; Balog, M. ; Simančík, F. ; Sklenička, Václav
This paper describes properties of Al 99.7% produced by PM. Powder green were prepared via CIP. The prepared powder about size less than 400 µm was compacted via conventional direct hot-extrusion (DE) at temperature of 450°C. Some extruded material was additionally processed by ECAP. The microstructural investigations were performed using OM and SEM equipped with EBSD unit. Examination of extruded powder compacts showed that during DE initial powder particles deformed into grains about size of 5 m. This material was further subjected to ECAP passes. The mechanical properties of this material were investigated using hardness measurements. In addition, creep tests in tension were conducted at temperature of 473 K and at the different applied stresses. The basic aim of this work is microstructure characterization and description of creep behaviour of powder aluminium prepared by DE. The further aim of this work is the evaluation of ECAP technique effect on mechanical properties of powder Al.
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