(武漢理工大學(xué) 新材料力學(xué)理論與應(yīng)用湖北省重點實驗室，武漢 430070)
摘 要: 為了研究高性能柱狀晶Cu-Al-Mn形狀記憶合金的高溫大變形加工能力，采用Gleeble 3500熱模擬試驗機(jī)，在變形溫度700~850 ℃和應(yīng)變速率0.01~10 s-1條件下，對柱狀晶Cu70.8Al18.6Mn10.6形狀記憶合金進(jìn)行熱壓縮變形，分析合金的動態(tài)再結(jié)晶行為。結(jié)果表明：隨著變形溫度升高和應(yīng)變速率的增大，合金逐漸在晶界處以晶界弓彎的形核開始機(jī)制發(fā)生動態(tài)再結(jié)晶，且動態(tài)再結(jié)晶晶粒個數(shù)和尺寸不斷增加。根據(jù)Zener-Hollomon參數(shù)分析可得，合金的熱變形激活能為Q=113.55 KJ/mol。當(dāng)應(yīng)變速率因子 ＜8時，合金發(fā)生動態(tài)再結(jié)晶；當(dāng)8≤ ≤16.34時，合金可能發(fā)生或不發(fā)生動態(tài)再結(jié)晶；當(dāng) ＞16.34時，合金不發(fā)生動態(tài)再結(jié)晶。結(jié)合合金的熱加工圖得到其熱加工最佳工藝參數(shù)：變形溫度和應(yīng)變速率區(qū)間分別為725~825 ℃和0.08~1 s-1。對比分析高溫軋制前后合金組織和性能發(fā)現(xiàn)，合金在820 ℃軋制變形75%后不發(fā)生動態(tài)再結(jié)晶，且軋后合金在室溫下仍具有8%左右的超彈性應(yīng)變，同時馬氏體相變開始應(yīng)力和峰值應(yīng)力均提高2倍多。因此，合金在稍低于動態(tài)再結(jié)晶溫度下進(jìn)行大變形加工后，不僅可以提高合金的強(qiáng)度，而且還可以較好地保留鑄態(tài)合金的優(yōu)異記憶性能。
關(guān)鍵字: Cu-Al-Mn形狀記憶合金；柱狀晶組織；動態(tài)再結(jié)晶；應(yīng)變速率因子；高溫軋制
（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
