Microstructure evolution and mechanical properties of a high strength Mg-11.7Gd-4.9Y-0.3Zr (wt%) alloy prepared by pre-deformation annealing, hot extrusion and ageing
Microstructure evolution and mechanical properties of a high strength Mg-11.7Gd-4.9Y-0.3Zr (wt%) alloy prepared by pre-deformation annealing, hot extrusion and ageing
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DOI：
10.1016/j.msea.2017.06.096
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发表时间：
2017-08
期刊：
影响因子：
6.4
通讯作者：
Zijian Yu;Chao Xu;J. Meng;S. Kamado
中科院分区：
文献类型：
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作者：
Zijian Yu;Chao Xu;J. Meng;S. Kamado
通过预变形退火、热挤压和时效处理，成功地研制出一种具有弱拉压屈服不对称性的高强度Mg-11.7Gd-4.9Y-0.3Zr（wt%）合金。研究了预变形退火对该合金组织演变和力学性能的影响。结果表明，预变形退火产生了大量的Mg 5 RE（RE：稀土）相颗粒，提高了动态再结晶（DRX）分数。预制Mg 5 RE颗粒不仅通过颗粒模拟形核（PSN）强化动态再结晶，而且在热挤压过程中通过促进晶粒细化促进连续动态再结晶（C-DRX）。在没有预变形退火的情况下，挤压态合金表现出376± 9.6MPa的高拉伸屈服强度（TYS），但由于由具有强基底织构的粗的未DRX晶粒和具有弱基底织构的细的DRX晶粒组成的双峰组织而具有4.3±0.1%的低断裂伸长率（EL）。T5处理后，TYS进一步增加至500±5.5 MPa，而EL降低至2.7± 0.4%。预变形退火1h后，由于动态再结晶分数的提高和基体织构的弱化，合金的强度和塑性达到了很好的平衡（TYS为343± 0.2MPa，EL为9.3±0.9%）。T5处理进一步将TYS增加到446±3.8 MPa，但将EL降低到3.0± 0.2%。所研究的合金具有良好的压缩性能，导致在弱拉压屈服不对称性。晶粒细化、Mg 5 RE和β′相以及溶质偏聚的SFs对合金的强化有贡献。
Abstract A high strength Mg-11.7 Gd-4.9 Y-0.3 Zr (wt%) alloy with a weak tension-compression yield asymmetry has been successfully developed by pre-deformation annealing, hot extrusion and ageing. The effects of pre-deformation annealing on the microstructure evolution and mechanical properties are studied. The results reveal that pre-deformation annealing generates a large number of Mg 5 RE (RE: rare earth) phase particles and raises the fraction of dynamic recrystallization (DRX). The preformed Mg 5 RE particles not only enhance the DRX by particle simulated nucleation (PSN), but also facilitate the continuous DRX (C-DRX) by promoting the grain subdivision during hot extrusion. Without pre-deformation annealing, the as-extruded alloy exhibits a high tensile yield strength (TYS) of 376±9.6 MPa but a low elongation to failure (EL) of 4.3±0.1% due to the bimodal microstructure consisting of coarse un-DRXed grains with strong basal texture and fine DRXed grains with weak basal texture. After T5 treatment, the TYS further increases to 500±5.5 MPa, whereas the EL reduces to 2.7±0.4%. An excellent balance of strength and ductility (TYS of 343±0.2 MPa and EL of 9.3±0.9%) can be realized by pre-deformation annealing for 1 h due to the raised fraction of DRX and the weakened basal texture. T5 treatment further increases the TYS to 446±3.8 MPa but reduces the EL to 3.0±0.2%. The studied alloy exhibits good compressive performance, resulting in a weak tension-compression yield asymmetry. The grain refinement, Mg 5 RE and β′ phases, and solute-segregated SFs contribute to the alloy strengthening.