(1. 南京工程學(xué)院 材料工程學(xué)院，南京 211167；
2. 南京航空航天大學(xué) 材料科學(xué)與技術(shù)學(xué)院，南京 210016)
摘 要: 交變載荷作用下在AZ31鎂合金疲勞裂紋尖端滲注磷酸鹽轉(zhuǎn)化液，研究磷酸鹽的沉積行為及其對(duì)AZ31鎂合金疲勞裂紋擴(kuò)展速率的影響。采用掃描電鏡(SEM)、能譜儀(EDS)、X射線衍射儀(XRD)觀察分析裂紋尖端的形貌和物相組成，并采用貼應(yīng)變片方法確定滲注磷酸鹽轉(zhuǎn)化液前后應(yīng)力強(qiáng)度因子的變化。結(jié)果表明：滲注的磷酸鹽轉(zhuǎn)化液在AZ31鎂合金疲勞裂紋尖端形成Zn3(PO4)∙4H2O及MgZnP2O7復(fù)合覆層，能改變疲勞裂紋尖端的應(yīng)力大小和分布狀態(tài)，使應(yīng)力強(qiáng)度因子降低約30%，從而有效地增強(qiáng)疲勞裂紋閉合效應(yīng)，降低或延滯AZ31鎂合金疲勞裂紋的擴(kuò)展。
關(guān)鍵字: AZ31鎂合金；磷酸鹽；疲勞裂紋擴(kuò)展；疲勞裂紋閉合
fatigue crack propagation in AZ31 magnesium alloy
（1. School of Material Engineering, Nanjing Institute of Technology, Nanjing 211167, China;
2. College of Material Science and Technology, Nanjing University of Aeronautics and Astronautics,
Nanjing 210016, China）
Abstract:Under alternate loads, a phosphate liquid was immersed into the fatigue crack tip of AZ31 magnesium alloy, the phosphate deposition behavior and effects of the phosphate film on the fatigue crack propagation rate at the fatigue crack tip of AZ31 magnesium alloy were investigated. The morphologies and phase constitutions of the phosphate deposition at the fatigue crack tip were characterized by scanning electron microscopy (SEM), energy spectrum analysis (EDS) and X-ray diffractometry (XRD), respectively. The stress-intensity factor values at the fatigue crack tip were compared with and without inmersing phosphate liquid by taking advantage of strain gauge. The results show that the phosphate( Zn3(PO4)∙4H2O and MgZnP2O7) films can be formed at the fatigue crack tip of AZ31 alloy through inmersing phosphate liquid, and the stress magnitude and distribution change after inmersing phosphate liquid at the fatigue crack tip of AZ31 alloy. The stress-intensity factor value decreases by about 30%, which effectively improves the fatigue crack closure, and reduces or arrearage the fatigue crack propagation.
Key words: AZ31 magnesium alloy; phosphate; fatigue crack propagation; fatigue crack closure
