Characterization of LaB₆ particulate-reinforced eutectic Al-12.6 wt% Si composites fabricated via mechanical alloying and spark plasma sintering

In this study, x wt% LaB₆ (x = 0, 2, 5 and 10) particulate-reinforced eutectic Al-12.6 wt% Si powders and composites were prepared from commercial Al, Si and LaB₆ starting materials via powder metallurgy methods. Mechanical alloying (MA) was conducted on the blended powders using a high-energy ball mill (at 1060 cycles/min) for 2, 4 and 8 h. Mechanically alloyed (MA'd) powders were subjected to cold pressing (CP, under 450 MPa) and spark plasma sintering (at 450 °C for 180 s) processes. Powder particle morphologies changed from flaky to semi-equiaxial shape after MA duration of 4 h. Calculations performed through the XRD patterns of Al phase revealed that the average crystallite size increased and the average lattice strain decreased with increasing MA duration and LaB₆ content. Spark plasma sintered (SPS'd) samples were examined in terms of composition, microstructure, densification and mechanical properties (hardness, yield strength, compressive strength and wear volume loss). Studies revealed that 4 h was the optimal MA duration and 10 wt% was the optimal reinforcement content for the LaB₆particulate-reinforcedAl-12.6 wt% Si composites with respect to their mechanical properties. Al-12.6 wt% Si-10 wt% LaB₆ sample had the highest hardness (1.72 ± 0.12 GPa), yield strength (373 MPa), compressive strength (578 MPa) and lowest wear rate (0.001 mm³/Nm) values among all SPS'd samples.