Influence of the sintering-current on the microstructure evolutions of W-Cr-Zr alloys during the SPS process

• W alloy with high density and fine grain is obtained under 904 A/cm 2 current via SPS. • The increasing current density accelerates the densification of the sample. • The increasing current density reduces the precipitation of Cr and promotes the re-dissolution of Cr. • The increasing current density avoids abnormal grain growth. Spark Plasma Sintering (SPS) is a fast densification technique assisted with electric current, was used to manufacture self-passivating tungsten alloys in the last few years. In order to clarify the effect of sintering current on grain growth and the formation of Cr-rich phase, the tungsten (W)-chromium (Cr)-Zirconium (Zr) samples were sintered at 1100 °C with different sintering current intensities: 528 A/cm 2 -904 A/cm 2 . The Cr-rich phase and average grain size of sintered W-Cr-Zr samples were characterized by XRD and SEM, respectively. When the current intensity increases, the Cr-rich phase content decreases. It relates to the short sintering time and to enhanced re-dissolution process of Cr. The relative densities and average grain size of sintered samples increase with increasing current intensity, which is attributed to the electric current, which in turn promotes the densification and grain growth by accelerating the atomic migration. Interestingly, an extraordinary grain growth at minimum current intensity (528 A/cm 2 ) has been detected. This is mainly due to the local high-density current flowing around pores and the induced local overheating effect. Acknowledging a rather benign effect of the current at initial sintering stages, this work represents the direct study of the effects caused by sintering current on the densification and microstructure evolution of the W-Cr-Zr alloys during the SPS process.