Effect of La2O3 addition on microstructure and mechanical properties of W-Ni-Cu tungsten heavy alloy

For the present investigation, Tungsten heavy alloys (WHAs), (90-x)W-6Ni-4Cu-xLa2O3 are synthesized using the powder metallurgy route by liquid phase sintering at 1400 °C for 1 hour in hydrogen atmosphere. The effect of variation of La2O3 (Lanthanum oxide) dispersion in W-Ni-Cu alloy (0, 0.1, 0.5, 1.0, 1.5, and 2.0 wt.%) on microstructural evolution was investigated using a scanning electron microscope (SEM) and transmission electron microscopy (TEM). The distribution of the tungsten, matrix, and La2O3 were analyzed using X-ray energy dispersive spectroscopy (EDS). The influence of La2O3 content on the densification behavior was also determined. The stereological quantifications were done on particle size and contiguity. The lowest W particle size was observed in sample of 2.0 wt.% La2O3 added WHA. However, this sample was found to have more porosity. The W particle size was reduced by about 30% with 2.0 wt.% addition of La2O3. The maximum value of bulk hardness of about 320 HV5 was observed in 1.0 wt.% La2O3 content WHA. The three-point bend test was performed to determine the bending behavior of these alloys. The alloy with 1.0 wt.% La2O3 showed the maximum compressive strength of 1481 MPa and bending strength of 1021 MPa. Fractography revealed W-W interface de-cohesion fracture mechanism to operate pre-dominantly. W particle cleavage fracture mode was observed to increase with the addition of La2O3 up to 1.0 wt.% in the WHAs.