细晶Cr-NbCr2合金的热稳定性

Thermal stability of fine-crystal Cr-NbCr2 alloy

摘要:

本文研究了通过机械合金化+热压工艺制备的细晶Cr-NbCr₂合金的热稳定性。结果表明：热暴露过程中,Cr基体的颗粒尺寸有一定程度的长大,而Laves相NbCr₂颗粒由于其高热稳定性无明显变化。随着热暴露的进行,Cr基体颗粒与Laves相NbCr₂颗粒间压应力增加,使得基体和Laves相中分别出现了位错和层错/孪晶结构。所有热暴露条件下的Cr-NbCr₂合金的强度均不低于热压态的。在800-1200℃热暴露50h后,Cr-NbCr₂合金仍保持了较高的屈服强度和良好的塑性。但随着热暴露时间的继续延长,此时颗粒的长大成为主导因素,使得Cr-NbCr₂合金的屈服强度和塑性明显下降。

Abstract:

Thermal stability of fine-crystal Cr-NbCr₂ alloy prepared by mechanical alloying and hot pressing was researched. The results show that the grain size of Cr matrix has a certain degree of growing up after the thermal exposure, while the particles size of Laves phase NbCr₂ has no obvious change due to its high thermal stability. At the same time, the dislocation in the Cr matrix and the stacking faults/twins in the Laves phase NbCr₂ particles appear in the as-thermally exposed microstructure because of the increase of the compressive stress between Cr matrix and NbCr₂ particles. The as-thermally exposed compressive strength is not lower than the as-hot pressed strength. The Cr-NbCr₂ alloy can still keep higher yield strength and plastic strain after thermal exposure from 800℃ to 1200℃ for 50h. However, the yield strength and plastic strain will decline obviously by further extending the thermal exposure time because of the increase of the grain size.