织构与表面形变强化协同作用下镁合金疲劳机理研究

The fatigue property of magnesium alloy is low, which limits its popularization and application in bearing parts. The plastic deformation mechanism of magnesium alloy can be controlled by temperature and texture, and synergizes surface deformation strengthening to obtain the stronger anti-fatigue effect on magnesium alloy. Based on this, Mg alloy without RE and Mg-RE alloy with different texture intensity are chosen to be research object in this project, different degree deformation is induced in the subsurface of the two alloys with different conditions by controlling mechanical surface treatment, and then investigate comparatively their the non-equilibrium severe deformation characteristics as twinning-detwinning, dislocation slip and twinning start sequence, dynamic recovery and recrystallization, texture, microhardness-depth profile, residual stress distribution and surface roughness etc.; The high-cycle fatigue properties of the studied alloys under different conditions are measured, and the influence law of surface characteristics on fatigue behavior of the two alloys will be analyzed quantitatively and statistically. The mechanisms of slip and twinning deformation, residual compressive stress generation and relaxation of the two alloys during mechanical surface treatment at different temperature (and fatigue process) will be revealed. Particular emphasis is put on elucidating the fatigue crack initiation and anti-fatigue mechanisms of magnesium alloy under the synergistic effect of texture and surface deformation strengthening. The results will be contributed to provide theoretical basis and practical reference for improving the fatigue property of magnesium alloys.

镁合金疲劳性能偏低，阻碍了其在承力运动零部件上的推广应用。通过变形温度和织构调控镁合金的塑性变形机制，并协同表面形变强化有望获得更强的抗疲劳强化效果。本项目以具有不同织构强度的非稀土镁合金和稀土镁合金为研究对象，通过工艺控制对试样表面进行不同程度的形变强化处理，对比研究两类镁合金表层非平衡剧烈形变过程中组织结构演变规律，包括孪生-去孪、位错滑移及孪生启动顺序、动态回复和再结晶、织构，以及分层显微硬度、残余应力、表面粗糙度等；测试不同状态合金的高周疲劳性能，阐明塑性变形层微细化组织和性能在疲劳失效过程中的定量作用机制；揭示两类镁合金经不同温度表面形变强化处理及后续疲劳过程中的塑性变形机制、残余压应力产生及松弛机制，重点探明织构与表面形变强化协同作用下镁合金的疲劳裂纹萌生和抗疲劳强化机理。研究结果将为探索提高镁合金疲劳性能奠定理论基础和提供实践借鉴。

本项目系统研究了表面形变层组织性能与喷丸工艺内在关联、镁合金高周疲劳行为与表面变形层组织性能定量关系、喷丸处理镁合金微观塑性变形机制、喷丸处理镁合金疲劳机理。建立了高温喷丸后镁合金表面粗糙度、残余应力、组织结构特征和显微硬度与工艺参数和试样初始状态的内在关联；揭示了喷丸处理试样在高温或疲劳实验后残余应力和显微硬度的松弛机理；阐明了不同温度喷丸处理ZK60和Mg–10Gd–3Y–0.5Zr镁合金的微观塑性变形机制和晶粒细化机理，得到了公开文献报道最高疲劳强度值260MPa；进而探明了织构与表面形变强化协同作用下镁合金的疲劳裂纹萌生机制、不同温度喷丸处理镁合金残余应力的产生以及松弛机理、以及织构与表面形变强化协同作用下镁合金的疲劳机理。开发了一种高温喷丸装备，并提出了提高镁合金高周疲劳性能的有效技术途径。研究成果应用到了某航天装备的研制，获得了工程应用，项目负责人刘文才作为核心人员获得2020年国防科技进步一等奖（4/15）、中国航天科技集团科技进步一等奖（4/15）和上海产学研合作一等奖（2/5）等奖励3项。共发表了标注本基金号的论文27篇，其中SCI收录论文23篇，申请发明专利7项，其中已授权5项；培养博士生2名和硕士生7名。从理论和技术层面上均达到了项目申请书中的预期目标。