Superplastic Deformation of AZ61 Magnesium Alloy having Fine Grains
Superplastic Deformation of AZ61 Magnesium Alloy having Fine Grains
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细晶AZ61镁合金的超塑性变形
DOI：
10.2320/matertrans.45.2537
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发表时间：
2004
影响因子：
1.2
通讯作者：
Y. Kojima
中科院分区：
文献类型：
--
作者：
Y. Yoshida;K. Arai;Shota Itoh;S. Kamado;Y. Kojima
采用等通道转角挤压(ECAE)工艺对挤压后的镁-6质量%Al-1质量%锌(AZ61)合金进行细化。合金挤压棒材在473K进行2次ECAE处理，然后在448K进行4次处理，使合金棒材的晶粒细化到1 mm以下，析出大量细小的Mg17Al12化合物相。随后，对ECAE处理后的试件的超塑性进行了研究。当应变速率分别高于1�10�4 S�1和1�10�3 S�1时，分别在423K和448K下获得了大于300%的断裂伸长率，低于Tm=2(Tm：合金的熔点)。也就是说，发生了低温超塑性。此外，在1�10�2 S�1的高应变速率下，在473K和523K的较低温度下，超塑性分别达到242%和398%。超塑性变形的激活能约为91kJ/�，接近纯镁的晶界扩散激活能。结果表明，该合金的超塑性变形机制为晶界扩散控制位错滑移的晶界滑移。
Extruded Mg-6 mass%Al-1 mass%Zn (AZ61) alloy was grain-refined utilizing Equal Channel Angular Extrusion (ECAE) processing. Initially, the extruded bar of the alloy was ECAE-processed 2-times at 473 K. Subsequently, it was processed 4-times at 448 K. As a result, the grains are refined to less than 1 mm and a large amount of fine Mg17Al12 compound precipitates. Subsequently, the superplastic properties of the ECAE-processed specimens were investigated. Large fracture elongations of over 300% are obtained at 423 K and 448 K, which is below Tm=2 (Tm: melting point of the alloy), at strain rates above 1 � 10 � 4 s � 1 and 1 � 10 � 3 s � 1 , respectively. That is, low temperature superplasticity occurs. Furthermore, at a high strain rate of 1 � 10 � 2 s � 1 , superplasticity occurs with the elongation of 242% and 398% at relatively low temperatures of 473 K and 523 K, respectively. In the extraordinarily elongated specimens, significant grain boundary sliding is observed with strain rate sensitivity of 0:3� 0:4. The activation energy for superplastic deformation is about 91 kJ/mol, which is close to that for grain boundary diffusion of pure magnesium. It is concluded that the superplastic deformation mechanism of the investigated alloy would be grain boundary sliding accommodated by dislocation slip controlled by grain boundary diffusion.