Low temperature sintering of 90W–7Ni–3Fe alloy with Cu additive： microstructure evolution and mechanical properties

Abstract

The paper explores the possibility of reducing the sintering temperature of the 90W–7Ni–3Fe alloy by introducing Cu without sacrificing the comprehensive mechanical properties. The effect of Cu content on the sintering behavior, microstructure and mechanical properties of the 90W–7Ni–3Fe alloy was systematically investigated in the range from 1250 to 1350 °C. The results indicate that Cu significantly decreased the liquidus temperature of the 90W–7Ni–3Fe alloy, which directly influence the sintering behavior. With increasing of Cu content, the sintering behavior of the 90W–7Ni–3Fe alloy changed from solid to liquid phase sintering. The relative density of sintered alloys obtained at 1350 °C increased consistently from 81.61% without Cu to 98.85% with Cu concentration up to 5 wt.%. The X–ray diffraction (XRD) and transmission electron microscopy (TEM) results reveal that, Cu diffused with γ–(Ni, Fe) phase during sintering process and this results in the formation of the γ–(Ni, Fe, Cu) phase, which is well bonded with W grains. The formation process of γ–(Ni, Fe, Cu) phase is also discussed. The tensile strength and hardness of the 90W–7Ni–3Fe alloys were improved obviously by adding Cu. At 1350 °C, the tensile strength of alloys with 5 wt.% Cu is as high as 864 MPa, which was four times than that of the alloy without Cu.

Keywords

• Tungsten heavy alloy
• Low temperature sintering
• Sintering behavior
• Microstructure
• Mechanical properties