Effect of Yttrium Addition on Microstructural Characteristics and Superplastic Behavior of Friction Stir Processed ZK60 Alloy
Effect of Yttrium Addition on Microstructural Characteristics and Superplastic Behavior of Friction Stir Processed ZK60 Alloy
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DOI：
10.1016/j.jmst.2013.10.031
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发表时间：
2013-12
影响因子：
10.9
通讯作者：
Z. Luo;G. Xie;Z. Ma;Guanglei Wang;G. Wang
中科院分区：
文献类型：
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作者：
Z. Luo;G. Xie;Z. Ma;Guanglei Wang;G. Wang
对ZK60和ZK60-Y镁合金挤压板材进行了搅拌摩擦加工，加工速度分别为1600转/分和200转/分。等轴再结晶组织的形成使ZK60和ZK60-Y合金的平均晶粒度分别为∼8.5和∼4.7μm。此外，在FSP ZK60合金中，FSP破碎并弥散了镁锌相和W相(Mg3Zn3Y2)相，溶解了镁锌相。在ZK60合金中加入稀土元素Y后，合金中的大角度晶界比例由%提高到90%，并出现了一定数量的孪晶。在450℃时，FSPZK60-Y合金的最大延伸率为1200%，最佳应变速率为3×10−3S−1，显著高于FSPZK60合金。这是由于FSP ZK60-Y合金中HAGBs含量较高的细晶和大量弥散分布的热稳定性较高的第二相粒子所致。超塑性数据分析和表面形貌观察表明，晶界滑移是FSP ZK60和ZK60-Y合金的主要变形机制。
As-extruded ZK60 and ZK60-Y magnesium alloy plates were successfully processed via friction stir processing (FSP) at a tool rotation rate of 1600 r/min and a traverse speed of 200 mm/min. FSP resulted in the formation of equiaxed recrystallized microstructures with the average grain sizes of ∼8.5 and ∼4.7 μm in the ZK60 and ZK60-Y alloys, respectively. Moreover, FSP broke and dispersed the MgZn2and W-phase (Mg3Zn3Y2) particles and dissolved MgZn2phase in the FSP ZK60 alloy. With the addition of rare earth element yttrium (Y) into the ZK60 alloy, the ratio of the high angle grain boundaries (HAGBs) in the FSP alloys increased from 64% to 90%, and a certain amount of twins appeared in the FSP ZK60-Y alloy. The maximum elongation of 1200% and optimum strain rate of 3 × 10−3s−1achieved at 450 °C in the FSP ZK60-Y alloy were substantially higher than those of the FSP ZK60 alloy. This is attributed to the fine grains with high ratio of HAGBs and the distribution of a large number of dispersed second phase particles with high thermal stability in the FSP ZK60-Y alloy. Grain boundary sliding was identified as the primary deformation mechanism in the FSP ZK60 and ZK60-Y alloys from the superplastic data analyses and surficial morphology observations.