Development of Nano-Tio2/Y2O3 Dispersed Zirconium Alloys By Mechanical Alloying Followed By Conventional and Spark Plasma Sintering

Abstract

Zirconium based alloys are attractive materials for high temperature applications mainly in the chemical and nuclear sectors due to their excellent corrosion resistance, good mechanical and thermal properties with very low neutron absorption. Minor addition of nano oxides in zirconium matrix enhances mechanical properties by dispersion strengthening and its grain boundary pinning results in better high temperature stability. Moreover, nano-sized oxide dispersion in the alloy suppresses the grain growth during annealing at high temperature results in the improvement of creep strength. The elevated temperature yield strength and corrosion resistance of zirconium alloys can be increased by dispersion of nano-TiO2/Y2O3. The present study deals with nano-TiO2/Y2O3 (1.0-2.0 wt. %) dispersed Zr based alloys with nominal compositions: Zr45Fe30Ni20Mo5 (alloy-A), Zr44Fe30Ni20Mo5 (TiO2)1 (alloy-B1), Zr44Fe30Ni20Mo4(TiO2)2 (alloy-B2), Zr44Fe30Ni20Mo5 (Y2O3)1 (alloy-C1) and Zr44Fe30Ni20Mo4(Y2O3)2 (alloy-C2) are synthesized by mechanical alloying (MA) in two ball mills (Mill-1: planetary and Mill-2: dual drive) followed by powder consolidation with conventional and spark plasma sintering (SPS) at 1400 oC and 900-1000 oC respectively. The microstructural and phase analysis of mechanical alloyed powders and consolidated products were studied by XRD, SEM/EDS and TEM followed by evaluation of physical (density), mechanical (compressive strength, hardness and wear resistance) and chemical (oxidation and corrosion resistance) properties. X-ray diffraction and TEM analysis reveal formation of different intermetallics of 10-30 nm size along with TiO2/Y2O3 (10-20 nm) throughout the matrix. Alloys consolidated by spark plasma sintering was found to possess high levels of compressive strength (825-1240 MPa) and hardness (10.38-16.85 GPa) which was 1.5-2 times higher than that obtained from conventional sintering. Addition of TiO2 and Y2O3 helps in enhancement of mechanical properties and effect of TiO2 was more prominent. Y2O3 dispersion displays better corrosion resistance, whereas, base alloy shows best oxidation property.