Microstructure development, mechanical behavior of pure Mo, Mo-Ni and nano Y 2 O 3 dispersed Mo-Ni alloys fabricated by mechanical alloying pressureless sintering

Abstract

Mechanical alloying is the candidate method for fabrication of Mo-Ni based alloys owing to wide difference in melting point and inadequate bilateral solubility. In the present investigation pure Mo, Mo90Ni10, Mo89Ni10 (Y2O3)1 alloys (all composition in weight%) have been synthesized by mechanical alloying for 10 h and consolidated by pressureless sintering method at 1400 °C and 1500 °C for 2 h. The study reveals the stepwise modification of microstructure to enhance the mechanical property by Ni and Y2O3 addition. Ni in Mo facilitates liquid phase sintering to enrich the densification, whereas Y2O3 addition refines the grain size and enhances the mechanical properties. The grain size distribution is bimodal with combined addition of Ni and Y2O3. Formation of Mo-Ni intermetallic is evident at the interface of Mo matrix. Maximum densification, hardness and strength are recorded as 90.44%, 8.73 GPa, 1.95 GPa respectively in Mo-Ni-Y2O3 alloys at 1500 °C owing to superior particle bonding at higher sintering temperature and dispersion strengthening mechanism. The fracture morphology is primarily particle shearing and microvoid formation, however mixed mode cracking (intergranular and transgranular) is observed in alloy Mo89Ni10(Y2O3)1. Most importantly the Y2O3 particles are dispersed along the interface and within the Mo matrix which is favorable for improving the toughness of the material.