Microstructures And Mechanical Properties Of SiC_p/2024Aluminum Matrix Composites By Repetitive Upsetting And Extrusion

Particle reinforced aluminum matrix composites exhibit unusual combinations ofmechanical and physical properties, such as high wear resistance, high specificstrength and low cost. They are widely used in automotive, aerospace, electronics andother industrial fields. In this paper, the SiCp/2024composites were prepared by stircasting process. Then SiCp/2024aluminum matrix composites were processed byrepetitive upsetting and extrusion (RUE) after hot extrusion. The microstructureevolution and the distribution of SiC particles in the composites after multi-passupsetting and extrusion were studied by optical microscopy (OM), scanning electronmicroscopy (SEM) and transmission electron microscopy (TEM). Mechanicalproperties of SiCp/2024composites after reciprocating upset deformation withdifferent passes were explored. The strengthening mechanism of as-RUE processedSiCp/2024aluminum matrix composite was analysed. The main conclusions weredrawn as follows:After repetitive upsetting and extrusion process, defects such as loose and holeswithin the composites prepared by stirring casting were nearly eliminated. The matrixwas effectively refined during the deformation. What’s more, the distribution of SiCparticles in the matrix was improved. Part of the SiC particles was broken by sheeringstress and the size of the particles changed from10~15μm to5~10μm. The grains inthe matrix were bended, broken or even ruptured by alternating shear,moreover duringthe RUE process,and a lot of grains had changed to subgrains, it led to the possibilityof sub-boundaries acting both as effective obstacles to deformation. The ultimatetensile(UTS) and yield strength(YS) of as-extruded SiCp/2024aluminum matrixcomposites were268MPa and212MPa,and the elongation was3.81%,mechanicalproperties of as-RUE SiCp/2024aluminum matrix composites increasedinitially,reached a peak and attained a constant, The UTS and YS of SiCp/2024aluminum matrix composites after4RUE pass reached the maximum value,increasingby40%and28%, and the elongation of SiCp/2024aluminum matrix composites after3RUE pass reached the maximum value. The fractures of the composites were mainlyinterfacial debondings and particles breakages after RUE pass.as-2RUE SiCp/2024composite after490℃/30min+165℃/18h heat treatmentprocess,and as-3RUE SiCp/2024composite after490℃/30min+165℃/16h heat treatment process SiCp/2024aluminum matrix composite get better mechanicalproperties. Room-temperature tensile test results showed that after heat treatment, theUTS and YS of as-heat treatment SiCp/2024aluminum matrix composites processedafter2RUE pass was357MPa and268MPa, respectively,compared with as-2RUESiCp/2024composite,increased by7%and6%.the UTS and YS of as-heat treatmentSiCp/2024aluminum matrix composites processed after3RUE pass was404MPa and321MPa, respectively,compared with as-3RUE SiCp/2024composite,increased by8%and7%.