(武汉理工大学 新材料力学理论与应用湖北省重点实验室，武汉 430070)
摘 要: 为了研究高性能柱状晶Cu-Al-Mn形状记忆合金的高温大变形加工能力，采用Gleeble 3500热模拟试验机，在变形温度700~850 ℃和应变速率0.01~10 s-1条件下，对柱状晶Cu70.8Al18.6Mn10.6形状记忆合金进行热压缩变形，分析合金的动态再结晶行为。结果表明：随着变形温度升高和应变速率的增大，合金逐渐在晶界处以晶界弓弯的形核开始机制发生动态再结晶，且动态再结晶晶粒个数和尺寸不断增加。根据Zener-Hollomon参数分析可得，合金的热变形激活能为Q=113.55 KJ/mol。当应变速率因子 ＜8时，合金发生动态再结晶；当8≤ ≤16.34时，合金可能发生或不发生动态再结晶；当 ＞16.34时，合金不发生动态再结晶。结合合金的热加工图得到其热加工最佳工艺参数：变形温度和应变速率区间分别为725~825 ℃和0.08~1 s-1。对比分析高温轧制前后合金组织和性能发现，合金在820 ℃轧制变形75%后不发生动态再结晶，且轧后合金在室温下仍具有8%左右的超弹性应变，同时马氏体相变开始应力和峰值应力均提高2倍多。因此，合金在稍低于动态再结晶温度下进行大变形加工后，不仅可以提高合金的强度，而且还可以较好地保留铸态合金的优异记忆性能。
关键字: Cu-Al-Mn形状记忆合金；柱状晶组织；动态再结晶；应变速率因子；高温轧制
（Hubei Key Laboratory of Theory and Application of Advanced Materials Mechanics, Wuhan University of Technology, Wuhan 430070, China）
Abstract:In order to study the high-temperature and large-deformation processing capability of high-performance columnar-grained Cu-Al-Mn shape memory alloys, the columnar-grained Cu70.8Al18.6Mn10.6 shape memory alloy was subjected to hot compression deformation (the deformation temperature of 700-850 ℃ and the strain rate of 0.01-10 s-1) to analyze the dynamic recrystallization behavior used the Gleeble 3500 thermal simulation testing machine. The results show that with the increase of deformation temperature and strain rate, dynamic recrystallization occurs at the grain boundary, and the number and size of dynamic recrystallized grains in the columnar-grained Cu70.8Al18.6Mn10.6 shape memory alloy increase. According to the Zener-Hollomon parameter analysis, it can be obtained that the thermal deformation activation energy of the alloy is Q=113.55 kJ/mol. When the strain rate factor ＜8, the alloy undergoes dynamic recrystallization; when 8≤ ≤16.34, the alloy may or may not undergo dynamic recrystallization; when ＞16.34, the alloy will not undergo dynamic recrystallization. Combining the hot working diagram of the alloy, the best process parameters of the hot working are obtained: the deformation temperature and strain rate ranges are 725-825 ℃ and 0.08-1 s-1, respectively. Comparative analysis of the structure and properties of the alloy before and after high temperature rolling shows that the alloy does not undergo dynamic recrystallization after 75% rolling deformation at 820 ℃. And the alloy still has a superelastic strain of about 8% after rolling, and the martensitic transformation critical stress and the peak stress are increased by more than 2 times at room temperature. Therefore, after large deformation at a temperature slightly lower than the dynamic recrystallization temperature, not only the strength of the alloy can be improved, but also the excellent memory performance of the as-cast alloy can be retained.
Key words: Cu-Al-Mn shape memory alloy; columnar-grained structure; dynamic recrystallization; strain rate factor; high temperature rolling
