High Density Of The W-ni-fe Alloy Mechanical Properties

Extensive research has been carried out on Tungsten-based heavy alloys (WHAs) because of their excellent mechanical properties and high densities. In this work, the effects of composition, sintering methods and heat-treatments on the mechanical properties of WHAs were systematically studied by means of optical microscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), tensile test, and impact test.Through investigating the effect of W content on the mechanical properties of WHAs sintered in hydrogen, it is shown that the tensile strength increases with W content increasing from 90%(weight fraction)to 95% and then decreases slowly with its further increase. And the elongation and impact toughness decrease with W content increasing from 90% to 97%. Through adding 0.5-1.5% Re in WHAs, it is shown that the tensile strength of WHAs increases considerably accompanying with the slow decreases of tensile elongation and impact toughness with Re content increasing to 0.5% and the tensile elongation and impact toughness decrease rapidly accompanying with the further increase of tensile strength with Re content increasing from 0.5% to 1.5%.By comparing the mechanical properties of specimens sintered in vacuum with those sintered in hydrogen, it is found that vacuum sintering leads to the increase of the mechanical properties of WHAs because of the elimination of hydrogen brittleness and the improvement of the wet properties for Ni-Fe bind phase during sintering. By investigating the effect of vacuum/pressure sintering on the mechanical properties of WHAs, it is found that the mechanical properties of WHAs are improved by vacuum/pressure sintering because of the elimination of hydrogen brittleness and the decrease of cavities.By investigating the effect of vacuum annealing on the mechanical properties of WHAs, it is found that vacuum annealing leads to the increase of the mechanical properties because of the elimination of hydrogen brittleness and the increase of the diffusion layer. Through investigating the effect of solid-solution/water-quench on the mechanical properties of WHAs, it is shown that the mechanical properties of WHAsare improved by solid-solution/water-quench because of the appearance of new phase. And it is also found that under solid-solution/water-quench state the best ratio of nickel to iron moved from 7/3 to 9/1 because the heat-treatment is effective to inhibit the precipitation of WNi4.