Synthesis, Microstructure and Mechanical Properties of Mo(Si1-xAlx)2/Al2O3 Composites

Abstract:

Mo(Si1-x,Alx)2/Al2O3 composites were prepared by combustion synthesis and hot-pressing sintering process. The combustion characteristics, phase composition, microstructure and mechanical properties of Mo(Si1-x,Alx)2/Al2O3 composites were investigated. The results show that the combustion synthesis mode, determined by image analysis, is spiral combustion in MoSi2 sample, however, those are chaos combustion in Mo(Si1-x,Alx)2/Al2O3 samples. X-ray diffraction analysis confirms that the main phase composition of combustion products are changed from tetragonal MoSi2 to hexagonal Mo(Si,Al)2 with the increasing of aluminum, and the diffraction peaks of Al2O3 can be identified in Mo(Si1-x,Alx)2/Al2O3 samples. The fracture toughness and bending strength are the maximum for Mo(Si0.90,Al0.10)2/10vol.%Al2O3, 4.25 MPa.m1/2 and 346 MPa, respectively, by a factor of 39% and 60% than the monolith MoSi2. The toughening and strengthening mechanism can be attributed to solid solution of aluminum alloying, alumina particle reinforcement, the remove of glass phase and intergranular fracture.

Key words:combustion synthesis; molybdenum disilicide; composites; alloying; mechanical properties