粉末粒度对一种新型镍基粉末高温合金热变形行为的影响

Effect of the Powder Size Distribution on the Hot Deformation Behavior of a Novel Nickel-based Powder Metallurgy Superalloy

利用EBSD、SEM、OM、热模拟试验机等对比研究了不同粉末粒度制备的一种新型镍基粉末高温合金(WZA3)在不同热压缩变形条件下的变形行为和组织差异性。结果表明:相比细粉制备的HIP-01样品而言,粗粉枝晶组织明显,成分偏析严重,其制备的HIP-02样品中残余粗大γ′较多。低温(1050、1080℃)高应变速率(1、0.1s-1)时,HIP-01样品峰值应力值高于HIP-02。热压缩后HIP-01样品边缘开裂情况较HIP-02严重,HIP-01样品保留了大部分原始热等静压组织,裂纹优先在粉末原始颗粒边界(priorparticleboundary,PPB)处产生,HIP-02样品边缘出现了部分再结晶组织。在1080℃/0.001 s^(-1)时,HIP-02样品峰值应力较HIP-01低约30 MPa,HIP-02样品热压缩过程再结晶现象明显,再结晶晶粒均匀,HIP-01样品出现项链晶组织,再结晶不充分。粗大γ′有利于促进1050和1080℃时HIP-02样品的再结晶。高温(1150℃)、低应变速率(0.001、0.01s^(-1))时,γ′全部溶解进基体γ中,两者热变形行为接近,样品均未出现开裂,组织全部发生完全再结晶,在1150℃/0.001 s^(-1)均出现异常长大晶粒。

The effects of the powder size distribution on the hot deformation behavior and the microstructural differences of a novel nickel-based powder metallurgy superalloy(WZ-A3) were studied by SEM,EDS,EBSD,OM,and the thermal simulation testing machine.The results show that compared with HIP-01 sample made from fine powder,the dendrite structure of coarse powder is obvious and the composition segregation is serious.The residual primary γ′ of the HIP-02 sample made from the coarse powder is more than that of the HIP-01 sample.At the low temperature(1050,1080 ℃) and high strain rates(1,0.1 s^(-1)),the peak stress of HIP-01 sample is higher than that of HIP-02 sample.After hot compression,the crack situation at the edge of HIP-01sample is more severe than that of HIP-02 sample.Most of the original microstructure of HIP-01 sample are retained,and the crack is generated at the prior particle boundary(PPB),while some recrystallized structure appear s at the edge of HIP-02 sample.At 1080 ℃/0.001 s^(-1),the peak stress of HIP-02 sample is about 30 MPa lower than that of HIP-01 sample.The recrystallization phenomenon of HIP-02 sample during hot compression is obvious and the recrystallized grains are uniform.The HIP-01 has necklace crystal structure,and the recrystallization is not sufficient.The coarse γ’ can promote the recrystallization of HIP-02sample at 1050 and 1080 ℃.At high temperature(1150 ℃) and low strain rates(0.001,0.01 s^(-1)),the γ’ dissolve into γ matrix,and the thermal deformation behavior of the two samples is similar.No cracks occur in the samples,and the microstructure is fully recrystallized.The abnormal grown grains are found in the both samples at 1150 ℃/0.001 s-1.