Abstract
This report describes the result of investigations on the improvement of the mechanical properties of W-Ni-Fe heavy alloys produced with optimum Ni/Fe ratio and the addition of suitable amount of Co to the basic composition of W-Ni-Fe heavy alloys. The aim of this project is to improve tungsten heavy alloys, particularly with regard to their ductility and strength. Microstructural characterization and room temperature tensile testing were performed on a series of tungsten heavy alloys containing 91.3 to 97.0 wt% tungsten. For these alloys, deformation and fracture behavior were studied via slow strain rate tensile testing at room temperature.
The strength and ductility at room temperature of the heavy alloys attained a maximum with Co content of about 0.5 wt% with the Ni/Fe ratio of about 4.0. The strength maximum resulted from a trade off between volume fraction strengthening and microstructure limited ductility.
Fracture surface observation indicated that the maximum strength correlated with the tungsten cleavage failure mode. At higer tungsten contents the tendency toward intergranular failure increased.
