Effect of Limited Additions of Y2O3, ZrO2 andAl2O3 on the Mechanical and Microstructure Characteristics of Tungsten Heavy Alloys

Abstract

In this experimental investigation, the effect of adding limited contents of yttrium oxide Y2O3 (0.02-0.5 % wt), zirconium oxide ZrO2 (0.1-0.5% wt), and aluminum oxide Al2O3 (0.5-3% wt) on the mechanical and microstructure properties of the tungsten heavy alloy (90W-7Ni-3Fe %wt).Elemental powders and oxide additives were mixed for 120 min. Green compact in the form of standard tensile and impact specimens were fabricated by applying uniaxial compaction under 200 MPa. Finally the specimens were sintered at 1480oC for 90 min under vacuum atmosphere. It was found that the addition of yttrium oxides in the order of 0.02-0.04% wt provides the highest improvements of both tensile strength and impact toughness. Moreover the addition of aluminum oxides in the order of 1% wt has strong effect in enhancing only the tensile strength, while the impact toughness is sensibly reduced. The addition of zirconium oxide in the non-stabilized form up to 0.5%wt reduces significantly the tensile properties. Furthermore, the addition of yttrium and zirconium oxides in the indicated ranges has no significant effect on the sintered density of compacts .On the other hand; the addition of aluminum oxides slightly reduces this density.