摘要
The strength-ductility inversion relationship of alloys is a persistent challenge in advanced materials design.Al-Cu series cast aluminum alloys that are considered as an exceptionally high-strength light alloy are not exclusive in structural applications due to their inherently poor plasticity.In this work,we employed a squeeze casting technique and Ca microalloying strategy for microstructure modulation to effectively address this difficulty.The addition of low concentrations of Ca(0.5 wt.%and 1 wt.%)elements to the as-cast Al-5Cu-0.5Mn alloy significantly enhances its plasticity by threefold at room temperature.Unexpectedly,even after T6 treatment,which typically compromises ductility for increased strength,the low-Ca micro-alloyed Al-5Cu-0.5Mn exhibited a further increase in its strength without sacrificing its ductility.The low-Ca addition to the alloy generates an ultrafine eutectic colony with a complex"coreshell"structure,which can serve as a carrier for localized stress transfer,effectively distributing the strain uniformly to more grains.Precipitation hardening of α-Al grains and spheroidization of lamellar ultrafine eutectic phases were simultaneously realized in the low-Ca alloy after T6 heat treatment,which resulted in comparable hardness of α-Al grains and eutectic colonies.The synergistic coordination of external strains through extensive strain-hardening induced by slip line and substantial microcrack generation by ultrafine eutectic colonies is evidenced by a series of in situ characterizations of the low-Ca alloys.Therefore,the uniform spreading deformation due to the transfer of strain-hardening effect and the alternating plastic deformation of α-Al grains and ultrafine eutectic colonies are the critical keys to overcoming the strength-plasticity paradox in low-Ca alloys.This study provides a perspective route for Al-Cu system cast aluminum alloys to be utilized as high-strength and tough structural materials.
基金
supported financially by the Science and Technology Innovation Leading Talent Project of Hunan Province(No.2020RC4013)
the"Technology Innovation 2025"Major Special Project of Ningbo City(No.2020Z033)
the Integrated Design of Composition-Structure-Forging of Large-Size and High-Loading Magnesium Transmission Casing for Next Generation Helicopter and Its Creep-Resistance Mechanism Investigation(No.U22A200616).
