不同的退火温度下NiAl-2.5Ta-7.5Cr合金显微组织的演变(英文)

Microstructural Evolution in Multiphase NiAl-2.5Ta-7.5Cr Alloy during Annealing at Different Temperatures

研究了NiAl-2.5Ta-7.5Cr合金在不同的退火温度下的组织演变过程,结果表明该合金的铸态组织是由NiAl基底中包含Ta（CrNiAl）2的大晶粒Laves相和一些富含Cr的尺寸在400-500nm的小颗粒组成,其中大晶粒Laves相晶界处存在C14结构相。NiAl中Ta和Cr的浓度分别在~0.6at%和~2.5at%之间。将合金置于1000°C度下退火,有细小的棒状C15结构的Laves相在NiAl中开始弥散析出。而合金经过1200°C度退火2h后,这种颗粒的体积分数增加,同时NiAl基底中Ta的浓度减少到~0.2at%。当退火温度增加到1400°C,NiAl基底中的Laves析出相完全消失。因此,1000-1300°C温度范围内这种Laves相在NiAl基底中的析出,可归因于Ti元素在NiAl固溶后的过度饱和后发生扩散的缘故。

The microstructure evolution of NiAl-2.5Ta-7.5Cr alloy during annealing at different temperatures was investigated.It is found that the microstructure of the as-cast alloy consists of coarse Laves phase Ta（CrNiAl）2 with C14 structure at grain boundaries and Cr-rich particles with sizes in the range of 400-500 nm in the NiAl matrix.The Ta and Cr concentrations in the NiAl are ~0.6% and ~2.5%（at%）,respectively.When the alloy is annealed at the temperature above 1000 °C,fine rod-like Laves phases with C15 structure begin to precipitate dispersively in the NiAl.After annealing at 1200 °C for 2 h,the volume fraction of the particles increases,and in the mean time,the Ta concentration in NiAl matrix reduces to ~0.2at%.As the annealing temperature further increases to 1400 °C,the Laves phase precipitates dissolve in the NiAl matrix completely.Therefore,the precipitation of Laves phase in NiAl during the annealing in the temperature range of 1000~1300 °C may be attributed to the diffusing followed by the supersaturation of Ta in NiAl after the solidification.