Effect of tungsten content on microstructure and mechanical properties of swaged tungsten heavy alloys

This paper describes the effect of tungsten content on microstructure and mechanical properties of swaged Co-containing tungsten heavy alloys with varying tungsten (90W-7Ni-2Fe-1Co, 93W-4.9Ni-1.4Fe-0.7Co and 95W-3.5Ni-1Fe-0.5Co). With increasing tungsten while tensile strength goes through a maximum, both percent elongation and impact energy decrease. Microstructure and fractographic analyses have been carried out in order to explain the trends in mechanical properties. Predominant transgranular fracture of tungsten grains combined with ductile dimple failure of the matrix in 90% W alloy is responsible for superior properties of this alloy in comparison to the alloy with 95% W. The highest tensile strength attained in 93% W alloy is attributed to predominant cleavage failure of W-grains. The results clearly indicate that the matrix volume fraction, contiguity and matrix mean path greatly influence the mechanical properties of tungsten heavy alloys.