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

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

摘要:

用带有能谱仪和电子背散射衍射仪（Electron Back-Scatter Diffractometer，EBSD）的扫描电子显微镜（Scanning Electron Microscope，SEM）、金相显微镜（Optical Microscope，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（WZ-A3）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/s、0.1/s）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（Prior Particle Boundary，PPB）处产生，HIP-02边缘出现了部分再结晶组织。1080℃-0.001/s时，HIP-02样品峰值应力较HIP-01样品低约30MPa，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/s、0.01/s）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，1150℃-0.001/s均出现异常长大晶粒。

Abstract:

The Scanning Electron Microscope (SEM) with energy dispersive spectrometer (EDS) and Electron Back-Scatter Diffractometer (EBSD), Optical Microscope (OM) and the thermal simulation testing machine were used to study the effect of the powder size distribution on the hot deformation behavior and the organizational differences of a novel nickel-based powder metallurgy superalloy (WZ-A3). The results show that: compared with powder preparation of HIP-01, the dendrite structure of coarse powder is obvious and the composition segregation is serious. The residual primary γ′ of the HIP-02 made by the coarse samples is more than the HIP-01. At the low temperature (1050℃, 1080℃) and high strain rates (1/s, 0.1/s), the peak stress of HIP-01 is higher than that of HIP-02. After hot compression, the crack situation at the edge of HIP-01 is more serious than that of HIP-02. Most of the original HIP-01 microstructure are retained, and the crack is generated at the Prior Particle Boundary (PPB), while some recrystallized structure appears at the edge of HIP-02. At 1080℃-0.001/s, the peak stress of HIP-02 sample is about 30MPa lower than that of HIP-01. The recrystallization phenomenon of HIP-02 during hot compression is obvious. The recrystallized grains of the HIP-02 are uniform. The HIP-01 has necklace crystal structure, and the recrystallization is not sufficient. The coarse γ" can promote the recrystallization of HIP-02 sample at 1050℃ and 1080℃. At high temperature (1150℃) and low strain rates (0.001/s, 0.01/s), 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 were found in 1150℃-0.001/s at the both two samples.