Characterization Investigations of 2 wt% LaB6 Particulate-Reinforced Al-7 wt% Si Matrix Composites Fabricated by Powder Metallurgy Methods

Abstract

In this study, first of all, sub-micron LaB6 reinforcing particles were synthesized in the size range of 100–500 nm via mechanochemical synthesis and leaching steps. Afterwards, Al-7 wt% Si matrix alloy and 2 wt% laboratory synthesized LaB6 powders were mechanically alloyed (MA’d) at different durations to constitute Al-7 wt% Si/2 wt% LaB6. Followed by compaction under a pressure of 450 MPa in a uniaxial cold press, samples were sintered at 570 °C for 2 h in flowing Ar gas atmosphere. Microstructural characterizations of the powders and sintered samples were performed using X-Ray Diffractometry (XRD) and Scanning Electron Microscopy (SEM) techniques. Effects of both MA (0, 1, 4 and 8 h) and LaB6 reinforcement (0 and 2 wt%) on the mechanical properties of the composites were determined in terms of microhardness and dry sliding tests. Both MA process and LaB6 reinforcement were found to make positive contribution to the hardness and wear resistance values. As-blended and sintered Al-7 wt% Si matrix alloy had a hardness value of 0.43 GPa. On the other hand, 8 h MA’d and sintered Al-7 wt% Si/2 wt% LaB6 composite had the highest hardness (0.97 GPa) and the 4 h MA’d one had the lowest wear rate (3.25 × 10−6 mm3/N mm) among all the sintered samples. The hardness and wear resistance values were increased by approximately 2 times in the 4 h MA’d and sintered Al-7 wt% Si-2 wt% LaB6 composite compared to its 1 h MA’d counterpart.