To study the hot deformation behavior of a new powder metallurgy nickel-based superalloy,hot compression tests were conducted in the temperature range of 1020−1110℃ with the strain rates of 0.001−1 s^−1.It is found t...To study the hot deformation behavior of a new powder metallurgy nickel-based superalloy,hot compression tests were conducted in the temperature range of 1020−1110℃ with the strain rates of 0.001−1 s^−1.It is found that the flow stress of the superalloy decreases with increasing temperature and decreasing strain rate.An accurate constitutive equation is established using a hyperbolic-sine type expression.Moreover,processing map of the alloy is constructed to optimize its hot forging parameters.Three domains of dynamic recrystallization stability and instability regions are identified from the processing map at a strain of 0.7,respectively.The adiabatic shear band,intergranular crack and a combination of intergranular crack and wedge crack are demonstrated to be responsible for the instabilities.Comprehensively analyzing the processing map and microstructure,the optimal isothermal forging conditions for the superalloy is determined to be t=1075−1105℃ andε&=10^−3−10−2.8 s^−1.展开更多
文摘分别采用氩气雾化(Argon atomization,AA)和等离子旋转电极(Plasma rotating electrode process,PREP)两种方法制备具有不同特性的镍基高温合金粉末,然后在相同条件下对两种粉末进行热等静压制备成块体材料(A-HIP及P-HIP)。分别对粉末和块体材料进行显微组织分析和形貌表征,并对热等静压材料在温度为1000~1100℃下、应变速率为0.01~1.0 s-1下进行热压缩实验,利用采集的应力、应变参数,通过迭代和线性回归的方法计算热激活能并构建本构方程,并利用所建立的本构方程预测合金在不同应变下的应力。结果表明:PREP粉末表面洁净度、球形度和粒径均匀度要比AA粉末的好,其表面氧含量也相对较低,仅为0.0079%,而AA粉末中氧含量为0.0139%(质量分数);相比P-HIP,A-HIP中分布着较多的原始颗粒边界和孔洞,原始颗粒边界的主要组成是大尺寸的γ′相和碳氧化物颗粒;A-HIP的平均晶粒尺寸为8.59μm,P-HIP的平均晶粒尺寸为12.54μm;A-HIP的强化相γ′的体积分数(43.91%)与P-HIP的强化相γ′体积分数(43.65%)基本相等。两种材料的激活能分别为1012.9 k J/mol和757.1 k J/mol,并采用双曲正弦Arrhenius模型构建不同应变下的本构方程并预测不同变形条件下的真应力,其与实验值间的绝对误差分别为6.46%和4.87%。A-HIP在压缩过程出现宏观裂纹,原始颗粒边界是压缩裂纹产生主要因素之一,且裂纹沿原始颗粒边界进行扩展。
基金Project(2016YFB0700300)supported by the National Key Research and Development Program of ChinaProject(51774335)supported by the National Natural Science Foundation of China。
文摘To study the hot deformation behavior of a new powder metallurgy nickel-based superalloy,hot compression tests were conducted in the temperature range of 1020−1110℃ with the strain rates of 0.001−1 s^−1.It is found that the flow stress of the superalloy decreases with increasing temperature and decreasing strain rate.An accurate constitutive equation is established using a hyperbolic-sine type expression.Moreover,processing map of the alloy is constructed to optimize its hot forging parameters.Three domains of dynamic recrystallization stability and instability regions are identified from the processing map at a strain of 0.7,respectively.The adiabatic shear band,intergranular crack and a combination of intergranular crack and wedge crack are demonstrated to be responsible for the instabilities.Comprehensively analyzing the processing map and microstructure,the optimal isothermal forging conditions for the superalloy is determined to be t=1075−1105℃ andε&=10^−3−10−2.8 s^−1.
