(1. 中南大學(xué) 材料科學(xué)與工程學(xué)院，長(zhǎng)沙 410083； 2. 中南大學(xué) 有色金屬先進(jìn)結(jié)構(gòu)材料與制造協(xié)同創(chuàng)新中心，長(zhǎng)沙 410083； 3. 中南大學(xué) 有色金屬學(xué)材料科學(xué)與工程教育部重點(diǎn)實(shí)驗(yàn)室，長(zhǎng)沙 410083)
摘 要: 對(duì)AZ61鎂合金進(jìn)行降溫多向壓縮變形，利用OM，SEM/EBSD及TEM技術(shù)對(duì)其晶粒細(xì)化和析出相變化進(jìn)行了觀察和分析。結(jié)果表明：在623~483 K溫度范圍內(nèi)降溫多向壓縮時(shí)AZ61鎂合金晶粒急劇細(xì)化，低角晶界通過(guò)吸收位錯(cuò)轉(zhuǎn)變成高角晶界，而降溫變形會(huì)明顯抑制晶粒長(zhǎng)大和晶界高角化，5道次變形后還存在大量中低角晶界，平均晶粒尺寸約為0.8 μm。變形初期析出的第二相尺寸較大，隨著變形道次的增加，第二相細(xì)化的同時(shí)數(shù)量明顯增多。降溫變形可促進(jìn)動(dòng)態(tài)析出，使得析出相分布更加細(xì)小、彌散。動(dòng)態(tài)析出使得AZ61相對(duì)AZ31鎂合金具有更高的硬度。AZ61鎂合金經(jīng)降溫變形后強(qiáng)度和延性得到同步提升，尤其是5道次變形后伸長(zhǎng)率顯著提高，這是細(xì)小第二相在中低角晶界上動(dòng)態(tài)析出造成的。
關(guān)鍵字: 鎂合金；多向壓縮；中低角度晶界；動(dòng)態(tài)析出
（1. School of Materials Science and Engineering, Central South University, Changsha 410083, China; 2. Nonferrous Metal Oriented Advanced Structural Materials and Manufacturing Cooperative Innovation Center, Central South University, Changsha 410083, China; 3. Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education, Central South University, Changsha 410083, China）
Abstract:Dynamic precipitation and its effect on grain refinement and mechanical properties of AZ61 Mg alloy during multi-directional forging in temperature range from 623 K to 483 K were investigated by OM, SEM/EBSD and TEM techniques. Dynamic precipitation of Mg17Al12 phase does happen at the early stage of multi-directional forging and grain size is significantly refined to 0.8 μm after five passes deformation. The initial size of precipitates is relatively big, and then precipitates become dispersed and are refined to nanometer scale. The nanometer dispersed precipitation retards the dislocation movement, along with the temperature decreasing, resulting in the high density of dislocations and low medium angle grain boundaries inside the grain. The strength and ductility of AZ61 Mg alloy are simultaneously improved after multi-directional forging under decreasing temperature. The dramatic improvement of ductility is found after the whole five passes deformation finished, which can be attributed to the dynamic precipitation occurring on the low or medium angle grain boundary.
Key words: magnesium alloy; multi-directional forging; low-medium angle grain boundary; dynamic precipitation
