Influence of the applied pressure on the microstructure evolution of W-Cr-Y-Zr alloys during the FAST process

Field assisted sintering technology (FAST) has been widely employed for powder materials consolidation. The assisted-current and applied pressure in FAST facility strongly affect the microstructures of the consolidated powder materials. In this work, the influence of the applied pressure on the W-11.4Cr-0.6Y-0.4Zr alloy during FAST consolidation at 1400 °C by varying the applied pressures (10 MPa-60 MPa) is investigated. The amounts of Cr-rich phase in W-Cr-Y-Zr sintered samples decreases with an increase of the applied pressure. This is owing to the local overheating, which enhances the Cr precipitation during the FAST process. In addition, the average grain size increases as the applied pressure rises from 10 MPa to 40 MPa. With the further increase of applied pressure to 60 MPa, the average grain size decreases. High applied pressure induces the deformation of the graphite punch, which results in a low thermal resistance. Therefore, the reduction of the grain size is mainly related to the low actual temperature of the sample. Under an applied pressure of 60 MPa, the high density (∼99.5 %), fine grain and homogeneous microstructure of W-11.4Cr-0.6Y-0.4Zr alloy can be obtained.