(1. 河北工業(yè)大學(xué) 材料科學(xué)與工程學(xué)院，天津 300130；2. 山東理工大學(xué) 材料科學(xué)與工程學(xué)院，淄博 255049；
3. 江蘇科技大學(xué) 冶金與材料學(xué)院，張家港 215600；4. 韓國材料科學(xué)研究院 輕合金組，韓國 昌原 51508)
摘 要: 基于開發(fā)低成本非稀土型變形鎂合金的目的，利用XRD、SEM、EDS、TEM和EBSD等檢測手段對新型Mg-7Bi-1Al-1Zn(質(zhì)量分?jǐn)?shù)，%，BAZ711)合金的微觀組織進(jìn)行相關(guān)表征，同時(shí)采用萬能試驗(yàn)機(jī)測試了其鑄態(tài)及擠壓態(tài)試樣的力學(xué)性能。結(jié)果表明：鑄態(tài)BAZ711合金中粗大的Mg3Bi2相呈連續(xù)網(wǎng)狀分布于α-Mg枝晶晶界處，其平均二次枝晶臂間距約為50 μm；擠壓態(tài)BAZ711合金發(fā)生完全再結(jié)晶，平均晶粒尺寸減小為3 μm，微米級Mg3Bi2相沿?cái)D壓方向呈條帶狀斷續(xù)分布，同時(shí)，基體中彌散分布有大量50~200 nm的近球狀或短桿狀Mg3Bi2相；擠壓后合金表現(xiàn)出典型擠壓織構(gòu)特征。由于組織細(xì)化和微/納雙尺度第二相的綜合強(qiáng)化作用，擠壓態(tài)合金力學(xué)性能較鑄態(tài)顯著提高，其拉伸屈服強(qiáng)度、抗拉強(qiáng)度和伸長率分別達(dá)到244 MPa、305 MPa和14%。
關(guān)鍵字: 鎂合金；熱擠壓；微觀組織；力學(xué)性能
（1. School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130, China
2. School of Materials Science and Engineering, Shandong University of Technology, Zibo 255049, China
3. School of Metallurgy and Materials Engineering, Jiangsu University of Science and Technology, Zhangjiagang 215600, China;
4. Light Metal Team, Korea Institute of Materials Science, Changwon 51508, Republic of Korea）
Abstract:In order to develop cost-effective Mg alloy without rare earth (RE) addition, the microstructural evolution of newly developed Mg-7Bi-1Al-1Zn (mass fraction, %, BAZ711) alloy was investigated by XRD, SEM, EDS, TEM and EBSD. The tensile test was also carried out to study corresponding mechanical properties. The results show that the as-cast BAZ711 alloy is consisted of α-Mg matrix with an average second dendrite arm space (SDAS) of about 50 μm and coarse Mg3Bi2 phases distributing in the grain boundaries. However, the average grain size is reduced to about 3 μm after extrusion. The extruded BAZ711 alloy with fully dynamic recrystallized (DRXed) grains contains strip-like fragmented Mg3Bi2 particles along the extrusion direction (ED), demonstrating a typical basal texture. In addition, a large amount of Mg3Bi2 precipitates with sizes ranging from 50nm to 200 nm were observed. The as-extruded BAZ711 alloy gives superior mechanical properties, a tensile yield strength of 244 MPa, an ultimate tensile strength of 305 MPa and an elongation of 14%, which is mainly due to grain refinement, and presence of micro/nano-size Mg3Bi2 particles.
Key words: magnesium alloy; extrusion; microstructure; mechanical property
