铜对热等静压钨合金微观组织和力学性能的影响

Effects of Cu on structure and properties of HIPed 90W-Ni-Fe-Cu tungsten heavy alloys

采用热等静压技术(HIP)制备90W-Ni-Fe-Cu合金,并通过SEM、TEM、EDS、EPMA和拉伸实验研究了铜对其微观组织和力学性能的影响。结果表明:随着铜含量的增加,合金烧结温度逐渐降低,实现了90W-Ni-Fe-Cu合金由固相烧结向液相烧结的转变。随着铜含量的增加,热等静压90W-Ni-Fe-Cu合金的拉伸强度和伸长率先增大后减小。铜含量为4%时,球形钨晶粒与γ黏结相均匀分布,拉伸强度和伸长率综合性能最优,分别为953MPa和7.65%,合金断裂方式主要由大量的钨解理断裂和黏结相延性撕裂组成;而当铜含量继续增加到6%时,由于铜对钨在黏结相中的溶解析出被抑制,γ黏结相中的钨含量降低,同时,高的静水压力将液相从钨晶粒间挤出,造成合金综合性能下降。

The 90W-Ni-Fe-Cu alloy was fabricated by hot isostatic pressing.The effects of Cu content on the microstructure and mechanical properties of 90W-7Ni-3Fe alloy were systematically investigated by SEM,TEM,EDS,EPMA and universal mechanical testing machine.The results indicate that,with Cu content increasing,the sintering temperature of 90W-7Ni-3Fe alloy decreases and the microstructure changes from solid phase sintering to liquid phase sintering.The tensile strength and elongation of 90W-Ni-Fe-Cu alloy firstly increase and then decrease with the increase of Cu.When the Cu content reaches up to 4%(mass fraction),the spherical tungsten grain and matrix phase are uniformly distributed,therefore the optimistic tensile strength and elongation(953 MPa and 7.65%,respectively)can be obtained.Its fracture mode is mainly composed of W cleavages and matrix ductile tearing.However,when the Cu content further increases to 6%(mass fraction),its mechanical properties decrease,which attributes to two reasons.Firstly,the solubility of W inγphase decreases due to the increase of Cu,therefore,the solution strengthen of W toγmatrix phase is weakened.Secondly,the liquid phase is extruded by hydrostatic pressure during sintering process,which resulting the inhomogeneous microstructure.