(1. 華南理工大學 國家金屬材料近凈成形工程技術(shù)研究中心，廣州 510640；
2. 華南理工大學 機械與汽車工程學院，廣州 510640)
摘 要: 對AZ91鎂合金鑄板進行攪拌摩擦加工，研究熱處理對被加工材料組織和力學性能的影響。結(jié)果表明，經(jīng)413 ℃保溫16 h固溶處理后，鑄態(tài)合金晶界處粗大的網(wǎng)狀β-Mg17Al12相基本溶入α-Mg基體中。在攪拌摩擦加工過程中，組織發(fā)生明顯細化，產(chǎn)生細小的等軸狀再結(jié)晶晶粒。預先固溶處理可使摩擦加工合金晶界處少量未溶β-Mg17Al12相全部溶入基體。隨后時效處理導致β-Mg17Al12相以兩種方式析出，時效初期以晶界處非連續(xù)析出為主，然后再發(fā)生晶粒內(nèi)部的連續(xù)析出。時效處理可較大程度地提高合金的硬度，以16 h最為顯著，攪拌區(qū)平均顯微硬度的最大值為118.4HV。預先固溶處理可以提高攪拌摩擦加工合金的塑性，伸長率為31.5%；隨后時效處理(16 h)則可以大幅度提高合金的抗拉強度，由攪拌摩擦加工板的265 MPa增至340 MPa。
關(guān)鍵字: AZ91鎂合金；攪拌摩擦加工；組織；力學性能；熱處理
（1. National Engineering Research Center of Near-net-shape Forming for Metallic Materials,
South China University of Technology, Guangzhou 510640, China;
2. School of Mechanical and Automotive Engineering, South China University of Technology,
Guangzhou 510640, China）
Abstract:AZ91 magnesium alloy sheet was subjected to friction stir processing (FSP), and the microstructure and mechanical properties of the experimental materials were investigated. The results show that coarse β-Mg17Al12 networks dissolve into the α-Mg matrix after solution treatment (ST) at 413 ℃ for 16 h. FSP results in the significant grain refinement and the generation of equiaxed recrystallized grains. Only a few β-Mg17Al12 phases are found at the grain boundaries in the FSP specimen, while these phases disappear in the pre-ST+FSP specimen. Two types of precipitates, i.e. discontinuous precipitation (DP) and continuous precipitation (CP), are found after aging treatment. The lamellar DPs are the dominant ones at the initial aging, and the CPs form within the grains. Aging treatment can improve the microhardness, with the maximum average value of 118.4HV (16 h). The pre-ST+FSP specimen shows excellent ductility with an elongation of 31.5%. Succedent aging treatment can remarkably improve the tensile strength of the alloy, which increases from 265 MPa in the FSP alloy to 340 MPa.
Key words: AZ91 magnesium alloy; friction stir processing; microstructure; mechanical property; heat treatment
