(1. 有研科技集團(tuán)有限公司 有色金屬材料制備加工國家重點實驗室，北京 100088；
2. 有研工程技術(shù)研究院有限公司，北京 100088；
3. 北京有色金屬研究總院，北京 100088)
摘 要: 以工業(yè)化擠壓生產(chǎn)大截面尺寸的ZM51鎂合金為研究對象，測試擠壓態(tài)和T6態(tài)合金沿擠壓方向(ED)的靜態(tài)力學(xué)性能，并在應(yīng)力比R=-1的條件下，研究T6態(tài)ED試樣的高周疲勞行為。結(jié)果表明：T6處理后，ED試樣的拉伸和壓縮強(qiáng)度均得到提升，但伸長率大幅降低，壓縮屈服強(qiáng)度的提高幅度遠(yuǎn)低于拉伸屈服強(qiáng)度的，合金拉壓屈服不對稱性增加。T6態(tài)ZM51鎂合金循環(huán)周次為1×107時的疲勞極限為103 MPa，約為其抗拉強(qiáng)度的30%。發(fā)生在裂紋尖端塑性區(qū)內(nèi)的“拉伸孿生-退孿生”是主要的疲勞損傷機(jī)制。合金疲勞裂紋的萌生位置以試樣表面附近的孿晶界為主，疲勞裂紋穿晶路徑擴(kuò)展。疲勞斷口兩側(cè)存在覆蓋整個斷口的針狀孿晶層，應(yīng)力越大，孿晶層厚度越小，而單個晶粒內(nèi)的針狀孿晶的數(shù)量越多，且間距越小。
關(guān)鍵字: 變形鎂合金；拉壓屈服不對稱性；高周疲勞；孿生；退孿生
（1. State Key Laboratory of Nonferrous Metals and Processes, GRINM Group Co., Ltd., Beijing 100088, China;
2. GRIMAT Engineering Institute Co., Ltd., Beijing 100088, China;
3. General Research Institute for Non-ferrous Metals, Beijing 100088, China）
Abstract:The industrially extruded ZM51 magnesium alloy was studied in the present work. The static mechanical properties of as-extruded and T6 treated samples along extrusion direction (ED) were tested, and the high cycle fatigue behavior of T6 ED samples were studied under stress ratio R=-1. The results show that the tensile and compressive strength of the ED sample are improved by T6 heat treatment, but the elongation is greatly reduced, and the increment of the compressive yield strength is much lower than that of the tensile yield strength, resulting in the rise in the yield-strength asymmetry. The fatigue strength of T6 treated ZM51 alloy is 103 MPa under 1×107 cycle conditions, which is about 30% of its tensile strength. The tensile twinning and detwinning mechanism play a dominate role in fatigue deformation process, which is occurred in the plastic zone of the crack tip. The fatigue crack mainly initiates at the twin boundaries near the specimen surface, and propagates in a trans-granular mode. There are a large number of needle twins on both sides of the fatigue fracture which cover the whole fracture. The larger the stress, the larger the number of needle twins, and the smaller the spacing. The thickness of twin layer near the fracture decreases with the increase of the stress.
Key words: wrought magnesium alloy; tension-compression yield asymmetry; high cycle fatigue; twinning; detwinning
