Investigation on variations of microstructures and mechanical properties along thickness direction of friction stir processed AA2014 aluminum alloy via ultra-rapid cooling-猫眼课题宝

超快冷搅拌摩擦加工AA2014铝合金厚度方向显微组织和力学性能变化研究

DOI：

10.1016/j.matchar.2021.111352

发表时间：

2021-09

期刊：

Materials Characterization

影响因子：

4.7

通讯作者：

中科院分区：

材料科学1区

文献类型：

作者：

Jian Wang;Ke Yang;Yang Zhang;Ya-lin Lu;Zhi-hao Bai;Xing-cheng Li

采用冷源辅助搅拌摩擦加工（CSA-FSP）技术，在不同冷却条件下实现了AA2014铝合金的细晶化。研究了液体co2诱导的冷却能力对搅拌区（SZ）沿厚度方向的组织演变和力学性能的影响。结果表明，液态co2冷却的FSP由于具有较高的应变速率、较高的冷却效率、较低的变形温度和较短的高温停留时间，可以在SZ上部区域形成细小的晶粒组织。整个SZ除CDRX和GDRX的主导机制外，表层DDRX和底层PSN的附加晶粒细化机制也有部分参与。随着冷却速度的增加，CSA-FSP 2014铝合金的强度和显微硬度均有所提高。液态co2冷却后，SZ上部区域的极限抗拉强度达到519.7 MPa，伸长率高达9.4%，比均匀化后的基体合金（246.7 MPa和4.3%）分别提高了110.66%和118.6%。细化和保留的第二相颗粒也可以进一步增强晶粒细化和位错积累效果，从而实现强度和塑性的良好结合。同时，定性评价了各种强化机制对CSA-FSP 2014铝合金整体强度的贡献

Fine-grained AA2014 aluminum alloy was innovatively achieved by cold source assisted friction stir processing (CSA-FSP) under different cooling conditions. The investigation detailedly addresses the effects of cooling capacity induced by liquid CO2on microstructural evolution and mechanical properties of the stirred zone (SZ) along thickness direction. The results indicated that FSP with liquid CO2cooling can provide fine grain structures in the upper region of SZ due to higher strain rate, higher cooling efficiency, lower deformation temperature and shorter high temperature residence time. Besides the dominant CDRX and GDRX mechanisms in the entire SZ, the additional grain refinement mechanism of DDRX in the surface region while PSN in the bottom region was partially involved. The strength and microhardness of CSA-FSP 2014 aluminum alloy were enhanced as the cooling rate increased. The ultimate tensile strength in the upper region of SZ cooled with liquid CO2achieved 519.7 MPa with a high elongation of 9.4%, which was 110.66% and 118.6% higher than that of the homogenized base alloy (246.7 MPa and 4.3%) due to the fine grain strengthening and second phase strengthening. The refined and retained second phase particles also can further enhance the grain refinement and dislocation accumulation effect, thus achieving an excellent combination of strength and plasticity. Meanwhile, the contribution of various strengthening mechanisms to the overall strength of CSA-FSP 2014 aluminum alloy was qualitatively evaluated