Effect Of B₄C, Si On Microstructure And Properties Of Tungsten Materials

Pure tungsten、W-B4C and W-Si alloys were prepared by the powder metallurgy method. Effect of pressing pressure, B4C and Si additions on the microstructure and mechanical properties of tungsten were studied in this work. The phase and microstructure of tungsten and its alloys were investigated by means of optical microstructure (OM), X-ray diffractometer (XRD) and scanning electron microscope (SEM) combination with energy dispersive spectrometer (EDS). Density and hardness were measured.The results show that the density and hardness of pure tungsten increase with the increase of pressing pressure, when the pressing pressure is 400MPa, the relative density and hardness of tungsten reach maximum with the value of 94.8% and 354.2MPa.The addition of B4C in tungsten can promote the sintering densification and inhibit the grain growth. With the increase of B4C, the relative density and hardness of W-B4C alloys increase, and the grain size decreases gradually. The relative density reaches maximum with the value of 98.9% when 1.0wt.% B4C is added and sintered at 2300℃. The vickers hardness reaches maximum with the value of 642.3MPa when 1.0wt.% B4C is added and sintered at 2200℃. The dispersed W2B can obtain during sintering process due to chemical reaction between B4C and W.Adding moderate amounts of Si in tungsten can promote the sintering densification and inhibit the grain growth. With the increase of Si, the relative density increase at first and then decrease, and the grain size decrease at first and then increase. The relative density reaches maximum with the value of 98.8% when 0.5wt.% Si is added and sintered at 2300℃. Si can reinforce the tungsten matrix by solid solution strengthening and precipitation strengthening. With the increase of Si, the vickers hardness of W-Si alloys increase gradually and reach maximum with the value of 727.3MPa when 1.Owt.% Si is added and sintered at 2200℃.