Microstructure and superplasticity of the as-cast Mg–9Al–1Zn magnesium alloy after high-ratio differential speed rolling
Microstructure and superplasticity of the as-cast Mg–9Al–1Zn magnesium alloy after high-ratio differential speed rolling
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DOI：
10.1016/j.msea.2016.09.063
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发表时间：
2016-11
期刊：
影响因子：
6.4
通讯作者：
Yong-Seog Kim;W. Kim
中科院分区：
文献类型：
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作者：
Yong-Seog Kim;W. Kim
采用大差速轧制（HRDSR）工艺对Mg-9Al-1 Zn（AZ 91）镁合金铸态组织进行轧制，可显著细化镁合金的晶粒尺寸，形成离异共晶β相，形成半网状组织。在HRDSR大变形过程中，由于离异共晶β相的破碎和分解，富Al α相在晶界和晶内析出了纳米级β相（50-100 nm）。在低于573 K的低温下，经HRDSR处理的AZ 91镁合金表现出优异的超塑性。最佳超塑性（最大拉伸伸长率为830%）是在573 K和1 × 10 - 3s-1下实现的。超过573 K，由于细小的β相颗粒溶解到基体中，导致晶粒尺寸的热稳定性降低，超塑性严重恶化。提出了超细晶AZ 91镁合金高温流变行为的理论模型。
The direct application of high-ratio differential speed rolling (HRDSR) on the cast microstructure of Mg–9Al–1Zn (AZ91) alloy resulted in significant refinement of grain size and divorced eutectic β-phase with semi-network structure. Nanosized β-phase particles (50–100 nm) precipitated at grain boundaries and within grains from the Al-rich α-phase, which formed as a result of fragmentation and decomposition of thedivorced eutecticβ-phase during severe plastic deformation by HRDSR. The HRDSR-processed AZ91 alloy exhibited excellent superplasticity at low temperatures below 573 K. The optimum superplasticity (with a maximum tensile elongation of 830%) was achieved at 573 K at 1 × 10−3s−1. Beyond 573 K, serious deterioration in superplasticity occurred due to a loss of thermal stability of grain size caused by the dissolution of the fine β-phase particles into the matrix. Models that can explain the high-temperature flow behavior of the ultrafine grained AZ91 alloy were proposed.