Bending fatigue behavior of thin Zr_(61)Ti_(2)Cu_(25)Al_(12)bulk metallic glass beams for compliant mechanisms application

作     者：Diao-Feng Li Ya-Long Yang Yong Shen Jian Xu Diao-Feng Li;Ya-Long Yang;Yong Shen;Jian Xu

作者机构：Institute of Metal ResearchChinese Academy of SciencesShenyang110016China School of Materials Science and EngineeringUniversity of Science and Technology of ChinaShenyang110016China 

出 版 物：《Journal of Materials Science & Technology》 (材料科学技术（英文版）)

年 卷 期：2021年第89卷第30期

页      面：1-15页

核心收录：

学科分类：08[工学] 0817[工学-化学工程与技术] 0806[工学-冶金工程] 080203[工学-机械设计及理论] 0805[工学-材料科学与工程（可授工学、理学学位）] 080502[工学-材料学] 0802[工学-机械工程] 0703[理学-化学] 0801[工学-力学（可授工学、理学学位）] 0702[理学-物理学] 

基　　金：supported by the National Natural Science Foundation of China under Grant No.51571192。 

主　　题：Metallic glasses Bending fatigue Crack initiation Crack propagation Compliant mechanisms 

摘      要：In this work,bending fatigue behavior of thinner Zr_(61)Ti_(2)Cu_(25)Al_(12)(ZT1)BMG beams with thicknesses of 500μm and 100μm were investigated with three-point bending(3PB),to evaluate the reliability and safety of this potentially material used in compliant mechanisms under cyclic bending load.Fatigue endurance limits(FELs)of ZT1 beams with thicknesses of 500μm and 100μm were determined to be 470 MPa,and~0.3 of its tensile strength.Fatigue life and FEL of ZT1 beams in bending are substantially independent of the beam thickness,in the scale from 500μm down to 100μm.Fatigue cracks of all ZT1 beams initiated at the extrinsic microvoids,either indirectly derived from surface scratches during mechanical polishing or originated from as-cast process.However,fatigue crack propagation behavior is highly related to the magnitude of cyclic stress level.By interrupted fatigue tests,larger proportion about 60-70%of fatigue life was spent on crack propagation under high stress level,while crack initiation occupied larger proportion about 80-85%under low stress level.The medium stress level of about 590 MPa almost shared the crack-initiation life and crack-propagation life.In addition,there are two crack deflection mechanisms during cracks steady propagation stage.One mechanism is crack deflection along the interacted shear bands ahead of crack-tip,the other one is crackjumpfrom one shear band to another shear band at a certain angle.These two mechanisms alternate dominate the crack propagation process,generating typical staircase-like crack propagation trajectory.Fatigue endurance limits of ZT1 beams in the form of either stress amplitude or strain amplitude are superior to traditional candidate materials in the field of compliant mechanisms,showing that the better reliability and larger deflection deformation can be achieved for flexible members made by ZT1 BMG even under cyclic loading.