Synthesis and mechanical properties of Nb and Al substituted MoSi₂

Abstract

A series of new non-equilibrium (Mo_1 − xNb_x)Si₂ (0 < x < 0·30), Mo(Si_1 − y,Al_y)₂ (0 < y < 0·30) and (Mo_1 − xNb_x)(Si_1 − y,Al_y)₂ (0 < x < 0·15, 0 < y < 0·15) alloys are prepared by combustion synthesis process in self-sustain mode. The phase transformation and mechanical properties of Nb and Al substituted molybdenum disilicide (MoSi₂) are investigated. The appropriate content of niobium addition in (Mo_1 − xNb_x)Si₂ system is 0 < x < 0·12, and the strength and toughness has an improvement from 250 MPa and 4·68 MPa m^1/2 to 380 MPa and 5·38 MPa m^1/2 corresponding to pure MoSi₂, respectively. The additions of aluminium can strengthen MoSi₂, but not toughen MoSi₂. The niobium and aluminium co-substituted MoSi₂ resulted in the similar results those of aluminium in MoSi₂.

Keywords:

• Intermetallics
• Silicides
• Powder metallurgy
• Combustion synthesis
• X-ray diffraction
• Mechanical properties