To explore the approaches of combined toughening and strengthening of the Al_3Ti-based L1_2 intermetallic alloys, multiphase Al_3Ti alloys formed by combining with reinforcement or by second phase precipitation are be...To explore the approaches of combined toughening and strengthening of the Al_3Ti-based L1_2 intermetallic alloys, multiphase Al_3Ti alloys formed by combining with reinforcement or by second phase precipitation are being studied. The interface reactions between Al_(66)Fe_9Ti_(25)matrix and SiC reinforcement were investigated. It is determined that SiC is chemically incompatible with the Al_(66)Fe_9Ti_(25)matrix, Al_2O_3 barrier coating on SiC by sol-gel process was developed to minimize the interfacial reactions. On the other hand, a new type of Al_3Ti-based alloy having a L1_2 matrix with second phase precipitation has been developed. The quaternary alloys based on Al_(66)Fe_9Ti_(25)and modified with Nb additions, consist of a L1_2 matrix and D0_(22) second phase in the annealed state ,but the second phase can be dissolved by solution treatment and precipitated during high temperature aging.展开更多
Effects of intermediate annealing temperature and time after hot working on recrystallization temperature （Tr） of Al-Mg-Sc-Zr alloy subjected to further cold working were investigated. It was found that Tr of cold w...Effects of intermediate annealing temperature and time after hot working on recrystallization temperature （Tr） of Al-Mg-Sc-Zr alloy subjected to further cold working were investigated. It was found that Tr of cold worked alloy dropped with the rise of intermediate annealing temperature or extension of annealing time, clue to coarsening of Al3（Sc, Zr） particles during intermediate annealing. After annealed at 550℃ for 1 h or 475℃ for 50 h, Tr is nearly same as that in a Sc, Zr free 5A06 alloy. Coarsening mechanism was also discussed. After hot rolling, residual dislocations promoted diffusion of Sc and Zr atoms at the elevated temperature of the intermediate annealing. Easier diffusion sped the growth of the AI3（Sc, Zr） particles, resulting in a coherency loss and quantity reduction of the particles.展开更多
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 mecha...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.展开更多
文摘To explore the approaches of combined toughening and strengthening of the Al_3Ti-based L1_2 intermetallic alloys, multiphase Al_3Ti alloys formed by combining with reinforcement or by second phase precipitation are being studied. The interface reactions between Al_(66)Fe_9Ti_(25)matrix and SiC reinforcement were investigated. It is determined that SiC is chemically incompatible with the Al_(66)Fe_9Ti_(25)matrix, Al_2O_3 barrier coating on SiC by sol-gel process was developed to minimize the interfacial reactions. On the other hand, a new type of Al_3Ti-based alloy having a L1_2 matrix with second phase precipitation has been developed. The quaternary alloys based on Al_(66)Fe_9Ti_(25)and modified with Nb additions, consist of a L1_2 matrix and D0_(22) second phase in the annealed state ,but the second phase can be dissolved by solution treatment and precipitated during high temperature aging.
基金The authors are grateful for the financial supports from the National Natural Science Foundation of China(No.51871111)the Natural Science Foundation of Shandong Province,China(No.ZR2018LE001)+1 种基金the Science and Technology Program of University of Ji’nan,China(Nos.XKY2036,XKY1713)the Key Research and Development Program of Shandong Province,China(No.2019GGX102008).
基金support by the Innovation Foundationof Chinese Academy of Sciences (Grant No CXJJ-205)
文摘Effects of intermediate annealing temperature and time after hot working on recrystallization temperature （Tr） of Al-Mg-Sc-Zr alloy subjected to further cold working were investigated. It was found that Tr of cold worked alloy dropped with the rise of intermediate annealing temperature or extension of annealing time, clue to coarsening of Al3（Sc, Zr） particles during intermediate annealing. After annealed at 550℃ for 1 h or 475℃ for 50 h, Tr is nearly same as that in a Sc, Zr free 5A06 alloy. Coarsening mechanism was also discussed. After hot rolling, residual dislocations promoted diffusion of Sc and Zr atoms at the elevated temperature of the intermediate annealing. Easier diffusion sped the growth of the AI3（Sc, Zr） particles, resulting in a coherency loss and quantity reduction of the particles.
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)+1 种基金the Science and Technology Development Program of Jilin Province(No.20200401030GX)the Natural Science Foundation of Jiangsu Province(No.BK 20220629)was greatly acknowledged.
文摘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.
