Prominent role of a high volume fraction of Mg17Al12 particles on tensile behaviors of rolled Mg–Al–Zn alloys
Prominent role of a high volume fraction of Mg17Al12 particles on tensile behaviors of rolled Mg–Al–Zn alloys
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DOI：
10.1016/j.jallcom.2017.08.289
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发表时间：
2017-12
影响因子：
6.2
通讯作者：
M. Zha;Hong-min Zhang;Cheng Wang;Huiyuan Wang;Zhang Enbo;Q. Jiang
中科院分区：
文献类型：
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作者：
M. Zha;Hong-min Zhang;Cheng Wang;Huiyuan Wang;Zhang Enbo;Q. Jiang
由于实现细晶组织的困难，用常规轧制方法制备具有超塑性&500%的镁合金板材仍然是一个挑战。更令人费解的是，位于晶界的软化的Mg17Al12粒子在高温下对超塑性起促进或抑制作用的作用迄今尚不清楚。采用常规轧制方法制备了高体积分数球形∼-9Al-1Zn(μ)(AZ91)(AZ3.0AZ3.0AZ3.0AZ9Al-1Zn)合金。轧制后的AZ91合金在室温下的抗拉强度为∼370℃，塑性为∼13%。更重要的是，在250℃和300℃时，分别获得了∼563%和∼735%的超塑性。认为镁铝锌合金的高温变形机制很大程度上取决于镁铝锌颗粒的数量。这项工作突出了高体积分数的Mg17Al12粒子在高温下沿晶界偏析的显著作用，它一方面可以有效地钉扎晶界，延缓晶粒粗化，另一方面有利于缓解晶间应力不相容，从而显著促进GBS行为。本研究对高超塑性轧制AZ91合金板材的工业应用具有重要的推动作用。
Fabricating magnesium alloy sheets exhibiting superplasticity >500% by conventional rolling remains a challenge due to the difficulty in achieving fine-grained structure. Even more puzzling is the role of softened Mg17Al12particles locating at grain boundaries, which play a promoting or retarding effect on superplasticity at elevated temperatures, has not been understood so far. Here, fine-grained (∼3.0 μm) Mg–9Al–1Zn (AZ91) alloy with a high volume fraction of spherical Mg17Al12particles was prepared by conventional rolling. The rolled AZ91 alloy exhibits a high tensile strength of ∼370 MPa and ductility of ∼13% at room temperature. More importantly, high superplasticity of ∼563% and ∼735% is achieved at 250 and 300 °C, respectively. It is recognized that the deformation mechanisms of the Mg–Al–Zn alloys at elevated temperatures depend significantly on the amount of Mg17Al12particles. This work highlights the prominent role of a high volume fraction of Mg17Al12particles segregating along grain boundaries at elevated temperatures, which on one hand can effectively pin grain boundaries to retard grain coarsening, and on the other hand, are beneficial to relax the intergranular stress incompatibility, and hence significantly facilitate GBS behavior. The current study promotes significantly the industry application of high superplastic rolled AZ91 alloy sheets.