91W-Ni-Fe-Co合金的常温、低温力学性能及微观组织

Mechanical properties and microstructure of 91W-Ni-Fe-Co alloys at room temperature and low temperature

通过粉末冶金方法制备91W-5.5Ni-3.3Fe-0.2Co和91W-5.5Ni-2.5Fe-1Co合金。采用硬度测试、室温低温拉伸试验、扫描电镜(SEM)和能谱(EDS)等方法,研究合金的微观组织演变和室温、低温力学行为。研究结果表明:在室温条件下,Co质量分数为1%的合金的力学性能更优异,抗拉强度和伸长率分别为1 400 MPa和11.7%,拉伸断裂行为以钨解理断裂和黏结相撕裂为主。微观组织上,相比于低Co合金,高Co合金的晶粒更加细小,钨-钨连续度降低,黏结相体积分数提高,黏结相中钨溶解度增大,合金性能得到优化;随着温度降低,2种合金的强度提高,伸长率下降;在-60℃时,高Co合金的伸长率相比于低Co合金的伸长率提高了20%,同时,合金的断裂模式仍以韧性相撕裂为主,而低Co合金在低于-20℃时,断裂由钨解理断裂主导。在一定范围内,Co质量分数增加能抑制杂质元素在晶界处偏聚,提高钨晶粒塑性变形程度,降低低温脆性。

91W-5.5Ni-3.3Fe-0.2Co and 91W-5.5Ni-2.5Fe-1Co alloys were prepared by powder metallurgy method.The microstructure evolution and mechanical behavior at room and low temperatures of the alloy were studied using methods such as hardness testing,tensile testing,scanning electron microscopy(SEM)and energy dispersion spectroscopy(EDS).The results show that at room temperature,the mechanical properties of the alloy with 1%Co mass fraction are better,the tensile strength and elongation are 1400 MPa and 11.7%,respectively.The tensile fracture behavior is mainly tungsten cleavage fracture and bonding phase tearing.In the microstructure,compared with low Co mass fraction alloy,the grain size of the high Co alloy is finer,the tungsten tungsten continuity decreases,matrix volume fraction increases,and the solubility of tungsten in the matrix increases.As the temperature decreases,the strength of the two alloys increases and the elongation decreases.At−60℃,the elongation of the high Co alloy is 20%higher than that of the low Co alloy,while the fracture mode of the alloy is still matrix rupture.However,the fracture of low Co alloy is dominated by tungsten cleavage fracture after the temperature is lower than−20℃.The increase of Co mass fraction in a certain range can inhibit the segregation of impurity elements at grain boundaries,increase the degree of plastic deformation of tungsten particles,and improve the low-temperature brittleness.