热力耦合作用下Al-2.8%Cu-1.35%Li-0.11%Zr合金析出相演化和力学性能

通过TEM、HAADF-STEM和室温拉伸实验开展Al-2.8%Cu-1.35%Li-0.3%Mn-0.11%Zr合金在人工时效和蠕变时效状态下的析出相演化规律和力学性能研究。结果表明,160℃时效条件下,人工时效和160 MPa应力时效过程中合金中析出相数量均随时效时间的延长而增多,相同时效时间条件下应力时效状态合金T_(1)相数量较多,但其平均直径减小了约5~15 nm。这主要是因为外加应力增加了合金中的位错密度从而促进析出相析出。T_(1)相在时效析出过程中并未受外加应力的影响而沿某个方向择优析出,无明显的应力位向效应,这可能与T_(1)相具有更大的惯习平面变体上的形核与临界应力值有关。相比于人工时效,应力时效后合金的室温屈服强度和抗拉强度均增加,且在时效初期对屈服强度效果更为显著。

Hybrid machine learning and microstructure-based approach for modeling relationship between microstructure and hardness of AA2099 Al−Li alloy

A hybrid approach combining machine learning and microstructure analysis was proposed to investigate the relationship between microstructure and hardness of AA2099 Al−Li alloy through nano-indentation,X-ray diffraction(XRD)and electron backscatter diffraction(EBSD)technologies.Random forest regression(RFR)model was employed to predict hardness based on microstructural features and uncover influential factors and their rankings.The results show that the increased hardness correlates with a smaller distance from indentation to grain boundary(D_(dis))or a shorter minimum grain axis(D_(min)),a lower Schmidt factor in friction stir weld direction(SF_(FD)),and higher sine values of the angle between{111}slip plane and surface(sinθ_(min)).D_(dis) and D_(min) emerge as pivotal determinants in hardness prediction.High-angle grain boundaries imped dislocation slip,thereby increasing hardness.Crystallographic orientation also significantly influences hardness,especially in the presence of T_(1) phases along{111}Al habit planes.This effect is attributable to the variation in encountered T_(1) variants during indenter loading.Consequently,the importance ranking of microstructural features shifts depending on T_(1) phase abundance:in samples with limited T_(1) phases,D_(dis) or D_(min)>SF_(FD)>sinθ_(min),while in samples with abundant T_(1) phases,D_(dis) or D_(min)>sinθ_(min)>SF_(FD).

中间形变热处理对铝锂合金短横向拉伸性能的影响

通过室温拉伸试验、扫描电镜(SEM)、X射线衍射分析(XRD)、背散射电子衍射技术(EBSD)、透射电镜(TEM)等手段对经过中间形变热处理工艺处理后的T84状态铝锂合金厚板的短横向拉伸性能及合金的显微组织进行了系统研究。结果表明,随冷压变形量的增加,合金短横向屈服强度和抗拉强度变化较小,延伸率先升高后降低。冷变形工艺提高了合金在随后热处理过程中的再结晶程度,降低了基体内粗大第二相的数量和尺寸,抑制了T_(1)相在晶界处的析出,晶粒形貌、粗大第二相和析出相共同影响了合金的短横向塑性。冷压变形量为20%时,合金的短横向屈服强度(R_(p0.2))为436 MPa、抗拉强度(R_(m))为543 MPa、延伸率为5.1%,具有最佳的强塑性匹配。