Effect of processing parameters on microstructure and mechanical properties of 90W–6Ni–4Mn heavy alloy

• A new, simple and convenient atmospheric controlling method was employed to fabricate full density 90W-6Ni-4Mn alloy.
• Densities of 99.65% for 90W-6Ni-4Mn alloys were obtained with grain size of 12.6 μm when sintered at 1250 °C for 60 min.
• Maximum tensile strength and elongation were 981 MPa and 20.6%, respectively.
• Higher sintering temperatures and longer holding times resulted in higher W content, solid volume fraction and contiguity.
• The insoluble gas would deteriorate the density and tensile properties of 90W-6Ni-4Mn alloy.

In the present work, 90W–6Ni–4Mn alloy was prepared by an atmospheric controlling method, which can avoid the oxidation of elemental Mn during sintering, to obtain full density. Different sintering temperatures and holding times were employed to optimize the sintering process. Relative densities higher than 99.0% were achieved for 90W–6Ni–4Mn sintered at temperatures of 1200–1300 °C with various holds. Nearly full density of 99.65% was acquired with an average W grain size of 12.6 μm as sintered at 1250 °C for 60 min. When subjected to tensile testing, this alloy exhibits an ultimate tensile strength of 981 MPa and elongation of 20.6%. Higher sintering temperatures and longer holding times resulted in higher W content in the matrix phase, solid volume fraction and contiguity, due to solution–reprecipitation and grain coalescence during liquid phase sintering. Moreover, under such a circumstance, the insoluble inert gas (argon) trapped in residual closed pores caused the pores to coarsen, deteriorating the density and tensile properties of 90W–6Ni–4Mn alloy. Accordingly, a suitable sintering cycle is fundamental for full density 90W–6Ni–4Mn alloy with mechanical properties comparable to conventional tungsten heavy alloys, but 200–250 °C lower sintering temperature.