Effect of Fe addition in W-Ni-Cu heavy alloy processed through powder metallurgy on microstructure and mechanical properties

In the present investigation, effect of Fe addition to 90 W-aNi-bCu-xFe, (where a/b was 6/4; x = 0, 0.5, 1.0, 1.5, and 2.0) on the microstructure and mechanical behaviour of Tungsten heavy alloys (WHAs) was undertaken. WHAs were fabricated via powder metallurgy processing. Sintering of green compact was done with a horizontal tubular furnace at 1400 degrees C under hydrogen atmosphere for 60 min. A synergetic effect of Fe dissolution in Ni-Cu binder on densification response was observed. The tungsten solubility in the matrix was measured using EPMA and found to decrease with the increase of Fe content. The tungsten particle size reduction of up to 20%, compared to 90 W-6Ni-4Cu heavy alloy, was observed. The bulk hardness measurements showed a maximum of about 332 HV5 for 2.0 wt% Fe containing W-Ni-Cu alloy. The mechanical properties, such as compressive and flexural/bending strength were determined by employing the uniaxial compression and three-point bend test and found to be 1732 +/- 36 MPa and 1147 +/- 22 MPa, respectively. Because of Fe content in the WHAs, lower volume % of the matrix and higher W-W contiguity in the microstructure resulted leading to superior compressive strength. Detailed fractography was done on all sintered WHA samples to understand the failure response during transverse loading. Fractography on fracture surface of bend tested samples was carried out. The separation of the W-W interface and W/W trans-granular failure was the predominant fracture mechanism observed.