Balanced strength and ductility by asymmetric gradient nanostructure in AZ91 Mg alloy  

作　　者：Bingqian Xu Jiapeng Sun Lingling Wang Jing Han Guosong Wu 

机构地区：[1]College of Mechanics and Materials,Hohai University,Nanjing 211100,China [2]School of Mechanical and Electrical Engineering,China University of Mining and Technology,Xuzhou 221116,China

出　　处：《Journal of Materials Science & Technology》2024年第17期167-179,共13页材料科学技术（英文版）

基　　金：supported by the Fundamental Research Funds for the Central Universities(No.B210202094);the Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.KYCX230661).

摘　　要：High-strength Mg alloys have historically suffered from a challenge in achieving good ductility.Here,we report an asymmetric gradient nanostructure design prepared by ultrasonic severe surface rolling(USSR)at room temperature.Unlike conventional gradient-nanostructured materials that employ a hard-soft-hard sandwich structure,this new design incorporates a combined gradient distribution of grain microstructure and nanoprecipitates throughout the entire sample along the thickness direction.The nanoprecipitates are identified as theβ-Mg_(17)Al_(12)phase and are primarily generated through In-situ pre-cipitation promoted by the USSR-induced high-density dislocations and temperature increment.Benefit-ing from this unique microstructure,an outstanding strength-ductility synergy is achieved,with a yield strength of 372.8 MPa,an ultimate tensile strength of 453.3 MPa,and an elongation of 11.5%.The en-hanced strength can be attributed to several mechanisms,including grain boundary strengthening,dislocation strengthening,precipitation strengthening,twin strengthening,and hetero-deformation induced(HDI)strengthening.The HDI hardening and activation of multiple deformation modes also contribute to good ductility.This work provides a promising and effective method for overcoming the longstanding strength-ductility trade-offdilemma in Mg alloys.

关 键 词：Mg alloy Strength-ductility synergy Gradient nanostructure Precipitates AZ91 

分 类 号：TG146.22[一般工业技术—材料科学与工程]