Background

High pressure die casting (HPDC) Mg alloy has a hetero-structure in which the microstructures gradually coarsen from the casting surface to the interior, leading to the different elastic–plastic (E-P) transitional behaviors among the layers.

Objective

In this paper, we quantitively determined the diverse E-P transitions among the HPDC layers and related them to the microstructural evolution.

Methods

To investigate independently the E-P transitional behavior of the layer, the surface, middle, and central layers were deliberately sliced in sequence from the casting surface to the interior of the HPDC Mg-4Al-5.7RE (in wt.%) component. The onset and the end of E-P transition in each layer were quantitively determined by cyclic tensile test and Kocks-Mecking analysis, respectively.

Results

It was found that the plastic deformation for all layers occurred in the first unloading loop near zero strain, indicating the start of the E-P transition. With increasing strain, the E-P transition ended first in the middle layer at 0.0081 strain due to the lowest fraction of the second phases and ended last at the small-grained surface layer at 0.0090 strain. Excluding the twinning-dependent anelastic strain, the E-P transitions ended in advance at the strains of 0.0059 and 0.0062 in the middle and surface layer, respectively.

Conclusions

A combination of cyclic tensile test and Kocks-Mecking analysis provided a method to quantitively determine the diverse E-P transitions among the HPDC layers resulted from the hetero-structure regarding grains, the second phases, and twins.

中文翻译：

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异质高压压铸镁铝稀土合金的弹塑性转变实验研究

背景

高压压铸（HPDC）镁合金具有异质结构，其中微观结构从铸造表面到内部逐渐变粗，从而导致各层之间不同的弹塑性（EP）过渡行为。

客观的

在本文中，我们定量确定了HPDC层之间的各种EP过渡，并将它们与微观结构演变相关。

方法

为了独立研究该层的EP过渡行为，有意从浇铸表面到HPDC Mg-4Al-5.7RE（按重量％）组分的内部依次对表面层，中间层和中心层进行了切片。通过循环拉伸试验和Kocks-Mecking分析分别定量确定每层中EP转变的开始和结束。

结果

结果发现，所有层的塑性变形均发生在接近零应变的第一个卸载回路中，这表明EP转变开始。随着应变的增加，由于第二相的分数最低，EP过渡首先在中间层以0.0081应变终止，最后在0.0090应变在小晶粒表面层终止。除了依赖孪晶的非弹性应变，EP过渡分别在中层和表层分别以0.0059和0.0062的应变结束。

结论

循环拉伸试验和Kocks-Mecking分析的结合提供了一种定量确定HPDC层中由晶粒，第二相和孪晶的异质结构导致的不同EP转变的方法。