Effects of cold pressing and extrusion on the microstructures and mechanical properties of SiC and B4C reinforced alumix-231 alloys

Abstract

In this research, mechanical and microstructure properties of cold pressing (CP) and extrusion (EXTR) specimens produced via powder metallurgy were investigated and compared. For this comparison, EXTR specimens were hot extruded at 565°C with an extrusion ratio of 4:1. Likewise, CP specimens were compacted under a pressure of 600 MPa and sintered at 565°C. Then, the effects of volume fraction on SiC and B<inf>4</inf>C particle reinforced Alumix-231 composites were investigated using optical microscopy, SEM and macro hardness testing. Compared to CP specimens, it was found that the hardness and mechanical strengths of Alumix-231 specimens without reinforcement produced using EXTR increased in the ratio of 140 and 190%, respectively. The test results showed that increase in uniformity of reinforcement dispersion and enhancement of interfacial bonding strength of the composites is the main reasons for the improvement of EXTR specimens. As a result, EXTR improves mechanical properties of the specimens by decreasing the porosity and thus increasing the density and interfacial bonding strength. © 2011 Academic Journals. © 2011 Elsevier B.V., All rights reserved.