新型Mg-Bi-Al-Zn變形鎂合金的微觀組織與力學性能

新型Mg-Bi-Al-Zn變形鎂合金的微觀組織與力學性能Microstructure and mechanical properties of new Mg-Bi-Al-Zn wrought magnesium alloy

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)量分數(shù)，%，BAZ711)合金的微觀組織進行相關(guān)表征，同時采用萬能試驗機測試了其鑄態(tài)及擠壓態(tài)試樣的力學性能。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相沿擠壓方向呈條帶狀斷續(xù)分布，同時，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。由于組織細化和微/納雙尺度第二相的綜合強化作用，擠壓態(tài)合金力學性能較鑄態(tài)顯著提高，其拉伸屈服強度、抗拉強度和伸長率分別達到244 MPa、305 MPa和14%。

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.

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