氢致微结构演变对高强Zr合金热加工软化效应的协同作用机理

The poor hot workability is the bottleneck for the further application of new 47Zr-45Ti-5Al-3V alloy. The preliminary research from our team found producing 47Zr alloy in gaseous mixture of hydrogen and argon (Melt hydrogenation) had greatly improved its hot workability, and the flowing stress drop is up to 50%. In view of this, we intend to prepare 47Zr alloy with different hydrogen content by melt hydrogenation. Through theoretical modeling and calculation, this project will establish the thermodynamic and kinetic model of hydrogen dissolution during melting process. The effect of hydrogen on the work hardening index and flow stress during high temperature compression were studied by dynamic thermal simulation. This project will study influence of hydrogen on its solidification structure and high temperature deformation mechanism. And this project will reveal the multiple influence mechanism of hydrogen on phase composition, dislocation and dynamic recrystallization. And clarify the interaction mechanism betweenphase composition, dislocation and dynamic recrystallization. Base on this, the synergistic mechanism of phase composition, dislocation and dynamic recrystallization with different hydrogen contents on the hot workability of 47Zr alloy will be revealed. Finally, the hydrogen content and mechanical properties of the 47Zr alloy were studied by vacuum dehydrogenation.This project will explore a simple, efficient and non-obvious method to change the composition of alloys during service, to improve the hot workability of 47Zr alloy, and provide theoretical basis and experimental guidance for breaking the application bottleneck of new high-strength Zr alloy.

热加工性能差是限制新型高强47Zr-45Ti-5Al-3V合金(47Zr)进一步应用的瓶颈。项目组前期探索研究发现，在氢-氩混合还原性气体中熔炼(液态置氢)制备的47Zr合金，其高温变形时流变应力降幅高达50%，热加工性能大幅提升。鉴于此，本项目拟采用液态置氢制备不同含氢量的47Zr合金，首先建立合金熔体氢溶解的热力学与动力学模型；研究氢对其凝固组织的影响规律；通过动态热模拟，研究氢对其高温变形机制的影响，揭示氢对微结构包括相组成、位错以及动态再结晶的多重影响机制；阐明微结构之间的交互作用机制；在此基础上，揭示不同氢含量下相组成、位错以及动态再结晶三者对47Zr合金热加工性能的协同作用机理；最后通过真空脱氢，研究其氢含量和力学性能的变化规律。探索一种简单、高效且不明显改变合金服役时成分的方法，来提高47Zr合金的热加工性能，为突破新型高强Zr合金的应用瓶颈提供理论依据和实验指导。

针对新型高强47Zr-45Ti-5Al-3V(ZrTiAlV)合金热加工性能差的问题，本研究采用液态置氢技术，即在氢-氩混合还原性气体中直接熔铸合金，将氢作为ZrTiAlV合金热加工时的临时合金化元素来提高其热加工性能。研究发现液态置氢降低了ZrTiAlV合金的β/(α + β)转变温度，增加了凝固组织中的β相含量，同时细化了初生β相尺寸。热模拟结果显示液态置氢明显降低了ZrTiAlV合金在(α + β)两相区内变形的峰值应力，显著提升了其热加工性能，并将其最佳热加工窗口由775-900℃和0.01-0.1s-1拓展至700-900℃和0.01-1s-1。高温变形组织分析结果表明液态置氢增加了β相含量，促进了位错滑移并激活了动态再结晶过程，进而导致其热加工性能显著提升。本项目实施阶段负责人及其团队计划发表SCI论文4~6篇，实际发表SCI论文14篇，协助培养硕士研究生1名，同时协助指导博士研究生和硕士研究生各1名。本项目相关研究成果对于提升ZrTiAlV合金热加工性能、降低其加工成本，并最终拓展ZrTiAlV合金的应用范围具有重要的参考价值。