Abstract: Using optical microscope， scanning electron microscope， and dilatometer etc， this work investigated the effects of alloy elements Nb and V on the austenite microstructure and expansion property of 4J32 alloy. The results indicated that when the addition amount of Nb was 0.1%， the pinning effect on the austenite grain boundaries was not apparent， and abnormal grains growth occurred in the specimens. However， when the addition amounts of Nb reached 0.3% and 0.4%， the microstructure of the specimens was homogeneous， and the average grain sizes decreased by 24.6% and 32.3%， respectively.When the addition amounts of V reached 0.3% and 0.4%， the grain sizes decreased by 14.4% and 16.3%， respectively. The refining ability of Nb on the austenite grains and the homogenization ability of the microstructure of the super Invar alloy were superior to those of V. When the addition amount of Nb reached 0.4%， NbC was mainly distributed along grain boundaries. When the addition amount of Nb was less than 0.4%， NbC distributed in a small amount within grains. The number and size of NbC precipitates increase with the increase in the Nb content. The average linear expansion coefficient α_{20-100 ℃}≤1.0×10^-6/℃ of the experimental alloys with the addition of Nb and V met the application requirements. Overall， the alloys with the addition amounts of 0.3% for both Nb and V showed a more appropriate combination of microstructure homogeneity， grain refinement， and expansion coefficient.

Key words: Super Invar Alloy, Nb and V Microalloying, Homogenization of Structure, Expansion Coefficient

摘要： 采用光学显微镜、扫描电子显微镜以及膨胀仪等方法，研究了合金元素Nb与V对4J32合金组织均匀性和膨胀性质的影响。结果表明，当Nb添加量为0.1%时，对奥氏体晶界的钉扎作用不够显著，试样出现晶粒异常长大的现象。而当Nb添加量分别达到0.3%与0.4%时，试样晶粒显微组织均匀，且平均粒径分别减小了24.6%与32.3%。V添加量分别达到0.3%与0.4%，晶粒尺寸分别减小了14.4%与16.3%。Nb对超因瓦合金奥氏体晶粒尺寸的细化能力和显微组织的均匀化能力优于V。当Nb添加量达到0.4%时，NbC主要沿晶界分布，当Nb添加量小于0.4%时，NbC在晶界内少量分布。NbC的析出数量和尺寸随着Nb含量的增加而增大。添加了Nb或V的试验合金的平均线膨胀系数α_{20-100 ℃}≤1.0×10^-6/℃满足使用要求。综合来说，Nb、V的添加量为0.3%的合金表现出良好的显微组织均匀性、晶粒细化和膨胀系数组合。

关键词: 超因瓦合金, Nb、V微合金化, 组织均匀化, 膨胀系数