YH2掺杂对粉末冶金Zr-Nb合金微观组织和力学性能的影响

Effect of YH2 Addition on Microstructure and Mechanical Properties of Zr-Nb Alloy Prepared by Powder Metallurgy

摘要:

粉末冶金法制备的锆基合金具有宏观缺陷少、成本低等优势，但粉末冶金锆基合金O含量较高、塑性差，成为制约其应用的主要障碍。本工作通过稀土氢化物掺杂降低合金基体O含量从而改善了粉末冶金锆基合金的塑性。以Zr-Nb合金为研究对象，研究了YH₂掺杂量对合金微观组织与力学性能的影响规律。结果表明，掺入的YH₂与合金基体中的O形成Y₂O₃，使得合金基体中的O含量显著降低。一方面，基体O含量的减少使合金保留了更多的塑性β相，有利于塑性的提升；另一方面，Y₂O₃颗粒的弥散分布及其钉扎晶界导致的晶粒细化对合金强度具有一定贡献作用。与未掺杂稀土的合金相比，添加2.4wt% YH₂的Zr-Nb合金动态压缩强度下降约16%，塑性提升了约140%。针对合金的O含量、各相含量以及晶粒尺寸对合金强度与塑性的影响进行了解耦分析。

Abstract:

Zr-based alloys prepared by powder metallurgy have the advantages of few macroscopic defects and low cost. However, the high content of oxygen and poor plasticity of this alloy have become the main obstacles restricting its applications. The plasticity of Zr-based alloys prepared by powder metallurgy was improved by doping rare earth hydrides to reduce the O content in alloy matrix. The effects of YH₂ addition content on the microstructure and mechanical properties of Zr-Nb alloys were investigated. The results show that the O content in the matrix is significantly decreased due to the Y₂O₃ formed by doped YH₂ with O in the matrix. On the one hand, more plastic β phase can be retained by the reduction of O content in matrix, which is beneficial to the improvement of plasticity. On the other hand, effects of the dispersion strengthening of Y₂O₃ particles and the grain refinement caused by dislocation pinning by formed Y₂O₃ can both contribute to the improvement of strength. Taking the Zr-Nb alloy added with 2.4wt% YH₂ as an example, the dynamic compressive strength is decreased by 16% and the plasticity is increased by 140% compared with the alloy without YH₂ addition. Decoupling analyses were conducted on the effects of oxygen content, phase composition and grain size on the strength and plasticity of the alloy.