基于同步辐射X射线的SiC颗粒/Al复合材料变形损伤
Synchrotron-based study on deformation and damage of SiC particles/Al composites with X-ray imaging

通过原位X射线成像系统研究了两种SiC粒径配比（45 μm和（45+100）μm）对70vol% SiC颗粒（SiCP）/Al复合材料变形损伤行为的影响。在准静态压缩加载下，利用X射线数字图像相关方法（XDIC）计算了SiCp/Al复合材料在不同变形阶段的应变场分布。宏观应力-应变曲线表明，因颗粒尺寸引起的SiCp/Al复合材料的强度差异较小，但粒径配比为45 μm的SiCP/Al的延展性明显优于（100+45）μm的SiCP/Al。细观应变场分析表明，粒径配比为（100+45）μm的SiCP/Al比45 μm的SiCP/Al更早出现变形损伤带，且前者在变形后期其应变场不均匀性更高。这是由于（100+45）μm SiCP/Al中更早在大颗粒附近出现应变集中点，而且这些集中点会迅速长大和汇聚进而形成宏观裂纹，导致材料更早失效和破坏。因此，减小颗粒尺寸和促进颗粒均匀分布有利于提高颗粒增强金属基复合材料的延展性。断口回收分析表明：两种颗粒尺寸的SiCP/Al复合材料的断裂模式都属于脆性断裂，且断口中都发现有颗粒破坏和界面脱粘现象存在。 Effect of SiC particle(SiCP) gradation (45 μm and (45+100) μm) on the deformation and damage of 70vol% SiCP/Al composites was studied by an in situ X-ray imaging system. The strain fields of SiCP/Al composites at different deformation stages under quasi-static loading were calculated by the X-ray digital image correlation method (XDIC). The bulk-scale stress-strain curves show that the difference in the yield strength of SiCP/Al composites with different particle gradations is small. But the ductility of 45 μm SiCP/Al is higher than that of (45+100) μm SiCP/Al. Strain field mapping suggests that deformation and damage localizations appear earlier in (45+100) μm SiCP/Al than in 45 μm SiCP/Al, and the strain fields for (45+100) μm SiCP/Al are more heterogeneous in the later deformation stages. The reason is that strain localizations tend to nucleate around big particles which grow and coalesce to form macroscopic cracks, leading to an earlier failure of (100+45) μm SiCP/Al. Hence, optimizing the particle size distribution helps improve the ductility of particle-reinforced metal matrix composites. The postmortem analysis indicates that the fracture modes of the two SiCP/Al composites are both brittle, characterized by particle breakage and interfacial debonding in the fracture plane. 国家重点研发计划（2017YFB0702002）；国家自然科学基金（11802252；11627901）；国防基础科研科学挑战专题（TZ2018001