(1. 中南大學(xué) 材料科學(xué)與工程學(xué)院，長沙 410083；
2. 中南大學(xué) 有色金屬材料科學(xué)與工程教育部重點(diǎn)實(shí)驗(yàn)室，長沙 410083)
摘 要: 采用光學(xué)顯微鏡、SEM/EBSD和組織定量分析技術(shù)研究AZ61鎂合金在623 K、3×10−5~3×10−1 s−1下單向壓縮時(shí)變形和動態(tài)再結(jié)晶行為。結(jié)果表明：AZ61鎂合金的流變應(yīng)力和動態(tài)再結(jié)晶行為強(qiáng)烈地受到應(yīng)變速率的影響；隨著應(yīng)變速率的提高，穩(wěn)態(tài)流變應(yīng)力對應(yīng)變速率的敏感性逐漸減弱，而峰值應(yīng)力對應(yīng)變速率的敏感性卻呈先減弱后又顯著增強(qiáng)的趨勢。提高應(yīng)變速率可加快動態(tài)再結(jié)晶進(jìn)程，但高速變形初期產(chǎn)生更多的粗大 孿晶，不利于完全再結(jié)晶而導(dǎo)致穩(wěn)態(tài)時(shí)的再結(jié)晶體積分?jǐn)?shù)反而較低；在中低應(yīng)變速率下動態(tài)再結(jié)晶以晶界弓出形核為主，而在高應(yīng)變速率下則主要通過孿晶分割來進(jìn)行；由應(yīng)變速率引起變形機(jī)制的變化是導(dǎo)致不同動態(tài)再結(jié)晶行為的原因。
關(guān)鍵字: AZ61鎂合金；高溫變形；應(yīng)變速率；動態(tài)再結(jié)晶；孿晶
AZ61 magnesium alloy
（1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
2. Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education, Central South University, Changsha 410083, China）
Abstract:The deformation and dynamic recrystallization behavior of magnesium alloy AZ61 were studied at 623 K and 3×10−5−3×10−1 s−1 by optical and SEM/EBSD metallographic observation. The results show that the flow stresses and the dynamic recrystallization behavior are dependent on strain rates. With the increase of the strain rate, the strain rate sensitivity becomes weaker for steady state stresses while the strain rate sensitivity for the peak stress decreases firstly then increases obviously. Increasing strain rate can accelerate the process of dynamic recrystallization and the development of coarse twins which are harmful to get a complete recrystallization structure leading to the decrease of fractional recrystallization. Bulging mechanism for dynamic recrystallization nucleation operates mainly at lower strain rate, whereas the dynamic recrystallization substructure developed at higher strain rate is characterized by twin intersections. The difference of deformation mode leads to the operation of different mechanisms of dynamic recrystallization nucleation.
Key words: AZ61 magnesium alloy; high temperature deformation; strain rate; dynamic recrystallization; twin
