首页|Balanced strength and ductility by asymmetric gradient nanostructure in AZ91 Mg alloy
Balanced strength and ductility by asymmetric gradient nanostructure in AZ91 Mg alloy
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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 the β-Mg17Al12 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,dis-location strengthening,precipitation strengthening,twin strengthening,and hetero-deformation induced(HD1)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-off dilemma in Mg alloys.
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