Effects of ZrC content and mechanical alloying on the microstructural and mechanical properties of hypoeutectic Al-7 wt.% Si composites prepared by spark plasma sintering

Abstract

This paper reports on the preparation of ZrC particulate-reinforced Al-7 wt.% Si composites by using a consecutive method of mechanical alloying (MA) and spark plasma sintering (SPS). Al, Si (7 wt.%), and ZrC (0, 2, 5, and 10 wt.%) powders were blended and mechanically alloyed (MA'd) for 4 h in a high-energy vibratory ball mill. Subsequently, SPS (at 450 °C for 210 s) was carried out on non-MA'd and MA'd powders. Dissimilar to the inhomogeneous microstructure of the non-MA'd powders, the 4 h MA'd powders exhibited a homogeneous morphology with semi-equiaxed particles that revealed a lower average crystallite size and higher average lattice strain. Furthermore, microstructural, physical, and mechanical characterizations were performed on the spark plasma sintered (SPS'd) composites. The mechanical characterizations showed that MA'd/SPS'd Al-7 wt.% Si-5 wt.% ZrC composite displayed the highest hardness and strength values among all the fabricated composites. It exhibited a hardness of 1.52 ± 0.16 GPa, yield strength of 327.56 ± 7.16 MPa, and compressive strength of 406.42 ± 2.82 MPa. Besides, the MA'd/SPS'd Al-7 wt.% Si-10 wt.% ZrC composite exhibited the lowest wear rate of 0.0022 mm 3 /N.m, which was approximately 46% of that of the unreinforced composite (0.0048 mm 3 /N.m). It can be stated that the addition of ZrC and application of MA effectively improved the microstructural and mechanical properties of the composites.