热处理对SLM AZ91D镁合金组织及腐蚀行为的影响  

Effect of Heat Treatment on Microstructures and Corrosion Properties of SLM AZ91D Magnesium Alloy

作　　者：崔博帅 王建刚[1] 张欣[1] 冯志浩 杨光 岳彦芳 李建辉[1,2,3] CUI Bo-shuai;WANG Jian-gang;ZHANG Xin;FENG Zhi-hao;YANG Guang;YUE Yan-fang;LI Jian-hui(School of Materials Science and Engineering,Hebei University of Science and Technology,Shijiazhuang 050000,China;Hebei Key Laboratory of Material Near-Net Forming Technology,Shijiazhuang 050000,China;Hebei Engineering Laboratory of Aviation Lightweight Composite Materials and Processing Technology,Shijiazhuang 050000,China)

机构地区：[1]河北科技大学材料科学与工程学院,石家庄050000 [2]河北省材料近净成形技术重点试验室,石家庄050000 [3]航空轻质复合材料与加工技术河北省工程实验室,石家庄050000

出　　处：《表面技术》2021年第3期323-329,365,共8页Surface Technology

基　　金：国防基础科研计划项目(Jcky2018407C004);河北省自然科学基金(E2017208128)。

摘　　要：目的研究热处理对激光选区熔化成形(Selective Laser Melting,SLM)AZ91D镁合金组织与耐蚀性能的影响。方法利用SLM技术成形了AZ91D镁合金,对试样进行固溶处理(T4)、固溶+时效处理(T6)。采用金相显微镜、扫描电镜、X射线衍射仪、电化学工作站分别对SLM、T4热处理、T6热处理的AZ91D镁合金试样的微观组织和耐蚀性能进行观察与测试。结果SLM试样经420℃保温6 h固溶处理后,β-Mg17Al12相基本固溶于基体中,晶粒尺寸由5μm增大至60μm左右。加热至200℃保温2 h时效处理后,β-Mg17Al12相从基体析出,随着时效时间由2 h增加至6 h,析出相数量逐渐增多。在3.5%NaCl溶液中浸泡120 h后,SLM试样表面腐蚀坑较小;T4热处理试样表面出现较大的腐蚀坑;T6热处理试样的表面腐蚀坑大小及深浅不一,腐蚀最严重。极化曲线结果表明,SLM试样的腐蚀电流密度Jcorr最小,为(1.889±0.2)×10^(–5)A/cm^(2),耐蚀性能最好;固溶+时效处理2 h的试样Jcorr最大,为(1.225±0.2)×10^(–4)A/cm^(2),耐蚀性能最差。不同热处理试样的耐蚀性能优劣排序为:SLM试样>T4试样>T6试样。结论未经热处理的SLM试样晶粒尺寸最小,耐蚀性最好。经420℃保温6 h固溶处理后,β-Mg17Al12相基本溶解,晶粒尺寸增大1个数量级;加热至200℃时效2 h处理后,耐蚀性最差,当时效时间继续延长至6 h后,β-Mg17Al12相的数量逐渐增多,耐蚀性能反而有所增强。This paper is devoted to investigate the effect of heat treatment on the microstructures and properties of resistance to corrosion of AZ91D magnesium alloy fabricated by Selective Laser Melting(SLM).The method adopted in this paper was to fabricate the samples of AZ91D magnesium alloy by SLM,and then solution treatment(T4)and solution-aging treatment(T6)were conducted,respectively.The microstructures and resistance to corrosion of AZ91D magnesium alloy samples with SLM,T4 solid solution and T6 solution-aging were tested and examined through metallographic microscope,scanning electron microscope,X-ray diffraction and electrochemical workstation.The results demonstarted that a substantial amount of theβ-Mg17Al12 phases were dissolved in the matrix,and the size of grains was increased from 5μm to 60μm after being treated with solid solution at 420℃for 6 hours.When the samples are heated to 200℃for 2 hours after aging treatment,theβ-Mg17Al12 phase precipitated from the matrix.Further,as the aging time being extended from 2 h to 6 h,the amount of precipitated phases were increased gradually.After being immersed in a solution of 3.5%NaCl for 120 hours,the corrosion pits on the surface of the samples were smaller,while larger corrosion pits appeared on T4 samples.In addition,the T6 samples demonstrated the most serious corrosion,with different sizes and depth of corrosion pits on the surface.The polarization curve of the samples showed that,Jcorr of the SLM sample was the smallest,with(1.889±0.2)×10^(–5) A/cm^(2),which also indicated the best resistance to corrosion.Jcorr of the samples treated by solution+aging for 2 hours was the largest,with(1.225±0.2)×10^(–4) A/cm^(2),indicating the worst corrosion resistance.As a result,regarding the resistance to corrosion in 3.5%NaCl solution,the order of corrosion resistance of different heat treatment samples is:the SLM sample>the T4 sample>the T6 sample.To summarize,the grain size of SLM samples was the finest and its resistance to corrosion was the best.Theβ-

关 键 词：AZ91D镁合金 激光选区熔化 固溶处理 时效处理 显微组织 耐腐蚀性 

分 类 号：TG166[金属学及工艺—热处理]