鎂合金組織與性能的影響
(1. 東北大學 理學院，沈陽 110004;
2. 東北大學 材料電磁過程研究教育部重點實驗室，沈陽 110004)
摘 要: 研究了熔煉時在熔劑(42%MnCl2+53%LiCl+5%CaF2, 質量分數(shù)，%)中添加稀土Er對鑄態(tài)AZ91鎂合金顯微組織、力學性能、斷口形貌以及腐蝕行為的影響。結果表明：在熔劑中添加稀土Er能夠去除鎂合金熔煉過程中產生的熔劑夾雜，凈化鎂合金熔體，提高鑄態(tài)AZ91鎂合金的拉伸性能和耐腐蝕性能；當熔劑中添加10 %的稀土Er時，鎂合金的抗拉強度σb和伸長率δ分別從156 MPa和1.8%上升到最大值220 MPa和4.1%；同時，鎂合金在5%NaCl水溶液中的腐蝕速率從1.20 mg/(cm2∙d)下降到最小值0.15 mg/(cm2∙d)；然而，隨著稀土Er在熔劑中添加量的進一步提高，合金中開始有φ-(Al7ErMn5) 和 τ-(Al66.7Mg23.3Er10)等含有稀土Er的相生成，消耗了合金中的Al和Mn元素，改變了β-(Mg17Al12)相的形態(tài)；而且沿枝晶界附近分布的粗大φ-(Al7ErMn5)相降低了枝晶之間的結合力，使得合金的σb和δ下降；同時，部分網狀的β-(Mg17Al12)相斷裂，呈離散的塊狀，導致合金的腐蝕速率增加；熔劑中添加稀土Er不改變鎂合金的斷裂機理，斷裂機制仍為準解理斷裂。
關鍵字: AZ91鎂合金；稀土Er；熔劑；力學性能
properties of casting AZ91
magnesium alloy
CUI Jian-zhong2, LE Qi-chi2
（1. College of Science, Northeastern University, Shenyang 110004, China;
2. The Key Laboratory of Electromagnetic Processing of Materials(EPM), Ministry of Education,
Northeastern University,Shenyang 110004, China）
Abstract:The effects of Er addition in the flux(42%MnCl2+53%LiCl+5%CaF2, mass fraction, %) on the microstructure, tensile properties, fractography, and corrosion behaviour of casting AZ91 Mg alloy were investigated. The results show that Er addition in the flux can eliminate the inclusions formed during smelting, purify the melt and improve the tensile properties and corrosion resistance. Using the flux mixed with 10% Er, σb and δ of the casting AZ91 magnesium alloy can be improved by purification from 156 MPa and 1.8% to the maximum value of 220 MPa and 4.1%, respectively. Meanwhile, the corrosion rate decreases from 1.20 mg/(cm2∙d) to the minimum value of 0.15 mg/(cm2∙d) in 5%NaCl solution. However, further increasing Er content in flux, φ-(Al7ErMn5) and τ-(Al66.7Mg23.3Er10) phase form, which can consume Al and Mn element in the alloy, and modify the morphology of β-(Mg17Al12) phase. The coarse φ-(Al7ErMn5) phase along dendrite boundaries can decrease the cohesion force between dendrites, which leads the tensile properties to decrease. In addition, some net-liked β-(Mg17Al12) phases become dispersive and nubble-liked, resulting in the increase of corrosion rate. The Er addition in flux cannot change the fracture mechanism of quasi-cleavage of AZ91 Mg alloy.
Key words: AZ91 magnesium alloy; rare earth of Er; flux; mechanical properties
