Table of Contents
ISRN Materials Science
Volume 2012, Article ID 180750, 8 pages
http://dx.doi.org/10.5402/2012/180750
Research Article

Microstructures and Mechanical Properties of Hot-Pressed M o S i 2 -Matrix Composites Reinforced with SiC and S i 3 N 4 Particles

School of Materials Science and Engineering, Central South University, Changsha, Hunan 410083, China

Received 24 September 2011; Accepted 23 October 2011

Academic Editor: U. Gomes

Copyright © 2012 Hongming Zhou et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

M o S i 2 -matrix composites reinforced with S i 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 M o S i 2 caused by the addition of SiC and S i 3 N 4 particles were found. The M o S i 2 composite with 20 vol.% SiC and 20 vol.% Si3N4 particles has the highest strength and toughness, which is about 100% and 340%, respectively, higher than that of pure M o S i 2 . The grain size of M o S i 2 decreases gradually with the volume content of SiC and S i 3 N 4 particles increasing from 0% to 40%, and M o S i 2 -20 vol% SiC-20 vol% Si3N4 composite exhibits the minimum grain size of M o S i 2 . The relationship between the grain size of M o S i 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.