Sc/Zr ratio-dependent mechanisms of strength evolution and microstructural thermal stability of multi-scale hetero-structured Al-Mg-Sc-Zr alloys  

作　　者：Min Zha Teng Tian Hai-Long Jia Hong-Min Zhang Hui-Yuan Wang 

机构地区：[1]Key Laboratory of Automobile Materials of Ministry of Education&School of Materials Science and Engineering,Nanling Campus,Jilin University,Changchun 130025,China [2]School of Mechanical Engineering and Rail Transit,Changzhou University,Changzhou 213164,China [3]International Center of Future Science,Jilin University,Changchun 130012,China [4]State Key Laboratory of Superhard Materials,Jilin University,Changchun 130012,China

出　　处：《Journal of Materials Science & Technology》2023年第9期67-78,共12页材料科学技术（英文版）

基　　金：supported by the Natural Science Foundation of China(Nos.51922048,52234009 and 51871108);Partial financial support from the Changjiang Scholars Program(No.T2017035);the Science and Technology Development Program of Jilin Province(No.20200401030GX);the Natural Science Foundation of Jiangsu Province(No.BK 20220629)was greatly acknowledged.

摘　　要：Microstructure and its thermal stability are critical in the development of high-performance Al-Mg alloys.Here,we attempt to tailor Al_(3)(Sc,Zr)precipitates and thus microstructure characteristics to manipulate mechanical properties and microstructural stability of Al-7Mg alloys fabricated by hot extrusion com-bined with two-pass hard-plate rolling via changing Sc/Zr ratio.Increasing Sc/Zr ratio leads to improved strength without any loss of ductility.A strength-ductility synergy,i.e.yield strength of∼548 MPa and ultimate tensile strength of∼605 MPa with an impressive ductility of∼10%elongation was achieved in the Al-7Mg-0.3Sc-0.1Zr alloy.The good strength-ductility synergy is ascribed to the multi-scale het-erogeneous microstructure promoted by the high Sc/Zr ratio,i.e.a bimodal grain structure,profuse low angle grain boundaries,dispersed nano-sized Al_(3)(Sc,Zr)precipitates coexisting with intragranular Mg-Zr co-clusters segregated at dislocations.Upon thermal exposure,the Al-7Mg-0.3Sc-0.1Zr alloy maintained higher hardness at below 250°C,whereas Al-7Mg-0.2Sc-0.2Zr and Al-7Mg-0.1Sc-0.3Zr alloys exhibited higher hardness in moderate-and high-temperature range of 250-350℃and≥400℃,respectively.Atom-probe tomography analysis illustrates that slow-diffusing Zr atoms enhance Al_(3)(Sc,Zr)coarsening resistance through forming a higher-content Zr-enriched protective shell around a Sc-enriched core in Al-7Mg-0.1Sc-0.3Zr.Meanwhile,the high Zr content promotes concurrent Al_(3)(Sc,Zr)precipitation during thermal exposure at high temperatures.The improved microstructural thermal stability in Al-7Mg-0.1Sc-0.3Zr alloy is further discussed in terms of the recrystallization resistance and grain growth behavior.The present study reveals the feasibility for designing high-strength and thermally stable hetero-structured Al-Mg-Sc-Zr alloys via tailoring Sc/Zr ratios for different application temperature ranges.

关 键 词：Al–Mg alloys Al_(3)(Sc Zr) Strength Thermal stability Bimodal grain structure 

分 类 号：TG146.21[一般工业技术—材料科学与工程]