To improve the understanding of coupling effect between dynamic recrystallization(DRX)behaviors and flow behaviors of as-cast AlCu4 SiMg, a finite element(FE) simulation equipped with the models of DRX evolution was i...To improve the understanding of coupling effect between dynamic recrystallization(DRX)behaviors and flow behaviors of as-cast AlCu4 SiMg, a finite element(FE) simulation equipped with the models of DRX evolution was implemented. A series of isothermal compression tests were performed primarily on a Gleeble-3500 thermo-mechanical simulator in a temperature range of 648-748 K and a strain rate range of 0.01-10 s-1.According to the measured true stress-strain data,the strain hardening rate curves(dσ/dε versus σ) were plotted to identify the critical strains for DRX initiation(εc). By further derivation of the related material constants, the DRX volume fraction equation and the strain for 50% DRX(ε0.5) equation were solved. Accordingly, the aforementioned DRX equations were implanted into the FE model to conduct a series of simulations for the isothermal compression tests. The results show that during the evolution of DRX volume fraction at a fixed strain rate, the strain required for the same amount of DRX volume fraction increases with decreasing temperature. In contrast, at a fixed temperature, it increases with increasing strain rate. Ultimately, the DRX kinetics model of AlCu4 SiMg alloy and the consequence of the FE analysis were validated by microstructure observations.展开更多
In this study,an AlCu/AlMgSc bimetallic alloy is prepared using a dual-wire arc direct energy deposition method and a triple heterogeneous microstructure(fine/coarse equiaxed grains/columnar grains)is constructed.Addi...In this study,an AlCu/AlMgSc bimetallic alloy is prepared using a dual-wire arc direct energy deposition method and a triple heterogeneous microstructure(fine/coarse equiaxed grains/columnar grains)is constructed.Additionally,a quantitative comparative analysis of the deformation behavior of triple and dual heterogeneous microstructures during interrupted tensile testing is conducted,with emphasis on the effects of grain morphology and size on the tensile deformation mechanisms in the heterogeneous microstructure.Compared with the AlCu alloy with a double heterogeneous microstructure(equiaxed/columnar grain),the AlCu/AlMgSc bimetallic alloy exhibits a higher ultimate tensile strength of 301.4±7.9 MPa,a yield strength of 181.3±1.4 MPa,and an elongation of 9.7%±1.3%,which correspond to increases by 19.4%,21.2%,and 24.4%,respectively.Interrupted tensile testing is performed and a quasi-in-situ approach is employed to investigate the plastic deformation mechanisms of the triple heterogeneous microstructure during tensile deformation.The density of geometrically necessary dislocations(GNDs)in the fine equiaxed grains and the rate of GND accumulation during deformation,surpassed those observed in coarse equiaxed and columnar grains.Furthermore,in micrometer-sized equiaxed grains,the ability to accumulate GNDs decreases as the equiaxed grain size increases,and the equiaxed grains exhibit a higher capacity to accumulate GNDs compared with columnar grains.The triple heterogeneous microstructure provides a more favorable environment for trapping GNDs,thus resulting in enhanced strength and plastic deformation capabilities.This study offers guidance for the formulation and engineering application of heterogeneous microstructure alloys with diverse grain morphologies and multiple length scales.Additionally,novel approaches are introduced to enhance the strength and ductility of Al alloys.展开更多
Al-Cu binary alloys are important and interesting industry materials.Up to date,the formation mechanisms of the key strengthening precipitates,namedθ’-phase,in the alloys are still controversial.Here,we report that ...Al-Cu binary alloys are important and interesting industry materials.Up to date,the formation mechanisms of the key strengthening precipitates,namedθ’-phase,in the alloys are still controversial.Here,we report that for non-deformed bulk Al-Cu alloys theθ’-phase actually has its own direct precursors that can form only at elevated aging temperature(>ca.200℃).These high-temperature precursors have the same plate-like morphology as theθ’-phase precipitates but rather different structures.Atomicresolution imaging reveals that they have a tetragonal structure with a=0.405 nm and c=1.213 nm,and an average composition of Al_(5-x)Cu_(1+x)(0≤x<1),being fully coherent with the Al-lattice.This precursor phase may initiate with a composition of Al5 Cu and evolve locally towards Al_(4)Cu_(2)in composition,eventually leading to a consequent structural transformation into theθ’-phase(Al4 Cu2=Al2 Cu).There are evidences that because of their genetic links in structure,such a high-temperature precursor may transform to theθ’-phase without having to change their morphology and interface structure.Our study reveals a well-defined and previously hidden precipitation scenario for theθ’-phase to form in Al-Cu alloys at an elevated aging temperature.展开更多
基金Project(cstc2016jcyjA0335)supported by Chongqing Foundation and Frontier Research,ChinaProject(P2017-020)supported by Open Fund Project of State Key Laboratory of Materials Processing and Die&Mould Technology,China
文摘To improve the understanding of coupling effect between dynamic recrystallization(DRX)behaviors and flow behaviors of as-cast AlCu4 SiMg, a finite element(FE) simulation equipped with the models of DRX evolution was implemented. A series of isothermal compression tests were performed primarily on a Gleeble-3500 thermo-mechanical simulator in a temperature range of 648-748 K and a strain rate range of 0.01-10 s-1.According to the measured true stress-strain data,the strain hardening rate curves(dσ/dε versus σ) were plotted to identify the critical strains for DRX initiation(εc). By further derivation of the related material constants, the DRX volume fraction equation and the strain for 50% DRX(ε0.5) equation were solved. Accordingly, the aforementioned DRX equations were implanted into the FE model to conduct a series of simulations for the isothermal compression tests. The results show that during the evolution of DRX volume fraction at a fixed strain rate, the strain required for the same amount of DRX volume fraction increases with decreasing temperature. In contrast, at a fixed temperature, it increases with increasing strain rate. Ultimately, the DRX kinetics model of AlCu4 SiMg alloy and the consequence of the FE analysis were validated by microstructure observations.
基金supported by the National Natu-ral Science Foundation of China(No.52205414)the Young Elite Scientists Sponsorship Program by CAST(No.2021QNRC001)+3 种基金the Advance Research Projects in the Field of Manned Spaceflight,China Manned Space Agency,China(No.040302)the Shang-hai Aerospace Science and Technology Innovation Fund Project,the Shanghai Academy of Spaceflight Technology,China(No.SAST2018-066)the 73rd batch of China Postdoctoral Science Foun-dation General Financial Support(No.2023MD734199)the Shaanxi Provincial Natural Science Basic Research Program(No.2023-JC-QN-0551).
文摘In this study,an AlCu/AlMgSc bimetallic alloy is prepared using a dual-wire arc direct energy deposition method and a triple heterogeneous microstructure(fine/coarse equiaxed grains/columnar grains)is constructed.Additionally,a quantitative comparative analysis of the deformation behavior of triple and dual heterogeneous microstructures during interrupted tensile testing is conducted,with emphasis on the effects of grain morphology and size on the tensile deformation mechanisms in the heterogeneous microstructure.Compared with the AlCu alloy with a double heterogeneous microstructure(equiaxed/columnar grain),the AlCu/AlMgSc bimetallic alloy exhibits a higher ultimate tensile strength of 301.4±7.9 MPa,a yield strength of 181.3±1.4 MPa,and an elongation of 9.7%±1.3%,which correspond to increases by 19.4%,21.2%,and 24.4%,respectively.Interrupted tensile testing is performed and a quasi-in-situ approach is employed to investigate the plastic deformation mechanisms of the triple heterogeneous microstructure during tensile deformation.The density of geometrically necessary dislocations(GNDs)in the fine equiaxed grains and the rate of GND accumulation during deformation,surpassed those observed in coarse equiaxed and columnar grains.Furthermore,in micrometer-sized equiaxed grains,the ability to accumulate GNDs decreases as the equiaxed grain size increases,and the equiaxed grains exhibit a higher capacity to accumulate GNDs compared with columnar grains.The triple heterogeneous microstructure provides a more favorable environment for trapping GNDs,thus resulting in enhanced strength and plastic deformation capabilities.This study offers guidance for the formulation and engineering application of heterogeneous microstructure alloys with diverse grain morphologies and multiple length scales.Additionally,novel approaches are introduced to enhance the strength and ductility of Al alloys.
基金the National Natural Science Foundation of China(Nos.51831004,51801060,51671082,11427806,51471067)the National Key Research and Development Program of China(No.2016YFB0300801)。
文摘Al-Cu binary alloys are important and interesting industry materials.Up to date,the formation mechanisms of the key strengthening precipitates,namedθ’-phase,in the alloys are still controversial.Here,we report that for non-deformed bulk Al-Cu alloys theθ’-phase actually has its own direct precursors that can form only at elevated aging temperature(>ca.200℃).These high-temperature precursors have the same plate-like morphology as theθ’-phase precipitates but rather different structures.Atomicresolution imaging reveals that they have a tetragonal structure with a=0.405 nm and c=1.213 nm,and an average composition of Al_(5-x)Cu_(1+x)(0≤x<1),being fully coherent with the Al-lattice.This precursor phase may initiate with a composition of Al5 Cu and evolve locally towards Al_(4)Cu_(2)in composition,eventually leading to a consequent structural transformation into theθ’-phase(Al4 Cu2=Al2 Cu).There are evidences that because of their genetic links in structure,such a high-temperature precursor may transform to theθ’-phase without having to change their morphology and interface structure.Our study reveals a well-defined and previously hidden precipitation scenario for theθ’-phase to form in Al-Cu alloys at an elevated aging temperature.
