Microstructures and Mechanical Properties of Hot-Pressed -Matrix Composites Reinforced with SiC and Particles

Abstract

MoSi 2 -matrix composites reinforced with Si 3 N 4 and SiC particles were fabricated by means of wet-mixing and heat-pressing process. Scanning electron microscope (SEM), X-ray diffractometry (XRD), polarizing microscopy, Vickers hardness tester, with a universal materials testing machine were used to investigate the morphology, grain size, hardness, fracture toughness, and bending strength of the synthesized composites. Notable effects on the bending strength and fracture toughness of MoSi 2 caused by the addition of SiC and Si 3 N 4 particles were found. The MoSi 2 composite with 20 vol.% SiC and 20 vol.% Si 3 N 4 particles has the highest strength and toughness, which is about 100% and 340%, respectively, higher than that of pure MoSi 2 . The grain size of MoSi 2 decreases gradually with the volume content of SiC and Si 3 N 4 particles increasing from 0% to 40%, and MoSi 2 -20 vol% SiC-20 vol% Si 3 N 4 composite exhibits the minimum grain size of MoSi 2 . The relationship between the grain size of MoSi 2 and bending strength is not entirely fit with Hall-Petch equation. The strengthening mechanisms of the composite include fine-grain strengthening and dispersion strengthening. The toughening mechanisms of the composite include fine grain, microcracking, crack deflection, crack microbridging, and crack branching.

Effect of Processing Conditions on the Microstructure, Mechanical Properties, and Corrosion Behavior of Two Austenitic Stainless Steels for Bioimplant Applications

“…Hall [28] proposed that the hardness dependence on grain size might follow the Hall-Petch relation directly [29,30]. Thus the hardness-grain-size relation could be described by:…”