时效对重度冷变形Ni-W-Co-Ta高密度合金组织和性能的影响

Effect of aging on microstructure and properties of severely colddeformed Ni-W-Co-Ta high-density alloy

在650~900℃温度区间内对重度冷变形Ni-W-Co-Ta高密度合金(总压下量90%)进行了16 h时效处理,借助扫描电镜、透射电镜、X射线衍射仪、拉伸试验机和显微硬度计对不同温度时效处理前后合金的微观组织和力学性能进行了表征,探究了时效温度对合金组织和性能的影响规律。结果表明,重度冷变形可将Ni-W-Co-Ta高密度合金的晶粒细化至纳米量级。时效处理后新相Ni_4W从基体析出,且该相的尺寸和体积分数随时效温度的升高逐渐增大。合金的力学性能指标随时效温度的升高先增大后减小。当时效温度为700℃时,合金强度达到最大值,相应的抗拉强度和屈服强度分别为2286和1989 MPa,显微硬度为765 HV。时效温度为750℃时,冷变形合金开始发生再结晶现象。合金时效处理前后断口形貌均呈现韧-脆混合型断裂特征。

The severely cold deformed Ni-W-Co-Ta high-density alloy(total reduction of 90%)was aged for 16 h in the temperature range of 650-900℃.The microstructure and mechanical properties of the alloy before and after aging at different temperatures were characterized by means of scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray diffractometer(XRD),tensile testing machine and microhardness tester,and the effect laws of aging temperature on the microstructure and properties of alloy were studied.The results show that the grains of Ni-W-Co-Ta high-density alloy can be refined to the nanometer level by severe cold deformation.The new phase Ni4W precipitates from the matrix after aging treatment,and the size and volume fraction of the phase increase with the increase of aging temperature.The mechanical properties indexes firstly increase and then decrease with the increase of aging temperature.When the aging temperature is 700℃,the strength of alloy reaches the maximum,the tensile strength and yield strength are 2286 and 1989 MPa,respectively,and the microhardness is 765 HV.Recrystallization of the cold deformed alloy occurs when the aging temperature is 750℃.The fracture morphology of the alloy before and after aging treatment presents the characteristics of ductile-brittle mixed fracture.