The tensile tests were conducted at room temperature using material test machine. The sensitivity of flow strength to strain rate was researched at strain rates of 0.001, 0.1, 0.6s-1 for Mg3Al1Zn2Y, Mg3Al2Zn2Y and Mg3A16Zn2Y. The sensitivity sequence of flow strength is Mg3A12Zn2Y ＞ Mg3Al1Zn2Y＞Mg3Al6Zn2Y. The rupture characteristics of magnesium alloys were described based on the fractal theory and technology of computer image disposal combined with scanning electron microscope. The results show that the fractal behavior of the alloys' fracture surface is remarkable. The brittleness, plasticity and the appearance of fracture surface can be related by the fractal dimension. The higher the fractal dimension, the better the alloy's plasticity, the more complex the fracture surface and the alloy inclines to ductile rupture. The sensitivity sequence of fracture surface to strain rate is Mg3Al2Zn2Y＞ Mg3A16Zn2Y＞Mg3Al1Zn2Y with positive or negative effect.%利用材料试验机开展了室温拉伸实验,在0.001,0.1,0.6s-1不同应变率下,研究了Mg3Al1Zn2Y,Mg3Al2Zn2Y与Mg3Al6Zn2Y合金流动应力的应变率敏感性,其大小为Mg3Al2Zn2Y＞ Mg3Al1Zn2Y＞ Mg3Al6Zn2Y.基于分形理论和计算机图像处理技术,结合扫描电镜分析,研究了合金断裂特征,结果表明:合金在不同应变率拉伸下的断口分形行为显著,分形维数可将断口的韧脆性与形貌特征联系起来,分形维数越大,合金塑性相对越好,合金越倾向于延性断裂,断口形貌也越复杂；三种合金断裂特性的应变率敏感性大小为Mg3Al2Zn2Y＞ Mg3Al6Zn2Y＞Mg3Al1Zn2Y,且表现出正负不同的应变率效应.
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