(湖南大學(xué) 材料科學(xué)與工程學(xué)院, 長沙 410082)
摘 要: 在應(yīng)變速率為0.005～5 s-1、 變形溫度為250～450 ℃條件下， 在Gleeble-1500熱模擬機(jī)上對AZ31鎂合金的高溫?zé)釅嚎s變形特性進(jìn)行了研究。結(jié)果表明： 材料流變應(yīng)力行為和顯微組織強(qiáng)烈受到變形溫度的影響； 變形溫度低于350 ℃時(shí)， 流變應(yīng)力呈現(xiàn)冪指數(shù)關(guān)系； 變形溫度高于350 ℃時(shí)， 流變應(yīng)力呈現(xiàn)指數(shù)關(guān)系； 變形過程中發(fā)生了動(dòng)態(tài)再結(jié)晶且晶粒平均尺寸隨變形參數(shù)的不同而改變，其自然對數(shù)與Zener-Hollomon（Z）參數(shù)的自然對數(shù)成線性關(guān)系；材料動(dòng)態(tài)再結(jié)晶機(jī)制受變形機(jī)制的影響， 隨溫度的不同而改變； 低溫下基面滑移和機(jī)械孿晶協(xié)調(diào)變形導(dǎo)致動(dòng)態(tài)再結(jié)晶晶粒的產(chǎn)生； 中溫時(shí)Friedel-Escaig機(jī)理下位錯(cuò)的交滑移控制動(dòng)態(tài)再結(jié)晶形核； 高溫時(shí)位錯(cuò)攀移控制整個(gè)動(dòng)態(tài)再結(jié)晶過程。 在本實(shí)驗(yàn)下， 材料的最佳工藝條件是：變形溫度350～400 ℃， 應(yīng)變速率為0.5～5 s-1。
關(guān)鍵字: AZ31鎂合金； 熱壓縮變形； 微觀組織； 動(dòng)態(tài)再結(jié)晶
AZ31 magnesium alloy at elevated temperature
（ School of Materials Science and Engineering,
Hunan University, Changsha 410082, China）
Abstract: Hot compression tests of AZ31 magnesium alloy were performed on Gleeble 1500 at strain rates ranged in 0.005-5 s-1 and deformation temperature 250-450 ℃. The results show that the flow stress behaviors and microstructures strongly depend on the deformation temperature. The relationship between flow stress and deformation temperature as well as strain rate can be represented by the exponential equation during temperature below 350 ℃, and by the power equation during temperature over 350 ℃. Dynamic recrystallization (DRX) takes place during the deformation process, and the average dynamically recrystallized grain size(drec) changes with deformation variables. The natural logarithm of drec is linear with the natural logarithm of Zener-Hollomon（Z）parameter. The mechanisms of DRX depend on the deformation mechanisms and change with temperature. Low-temperature DRX is associated with the operation of basal slip and twinning. At intermediate temperatures, cross-slip of α dislocations by Friedel-Escaig mechanism controls the nucleation of DRX. At high temperatures, the operating DRX mechanisms is controlled by dislocation climb. In the present work the good deformation condition is temperature of 350~400 ℃ with stain rate of 0.5-5 s-1.
Key words: AZ31 magnesium alloy; hot compression deformation; microstructure; dynamic recrystallization
