Taking extruded Al–Zn–Mg–Cu alloy(7A04 alloy) bars as the research object, the effect and mechanism of pre-annealing treatments on the microstructure and mechanical properties of the aged alloy bars were investigat...Taking extruded Al–Zn–Mg–Cu alloy(7A04 alloy) bars as the research object, the effect and mechanism of pre-annealing treatments on the microstructure and mechanical properties of the aged alloy bars were investigated. The results show that a pre-annealing treatment at 350°C for 15 h before a T6 treatment substantially reduced the sensitivity of the microstructure and mechanical properties of the extruded 7A04 aluminum alloy specimens toward the extrusion temperature. The average grain sizes of the specimens extruded at 390 and 430°C after T6 treatment were 3.4 and 8.1 μm, respectively, and their elongations to failure were 7.0% and 9.2%, respectively. However, after pre-annealing + T6 treatment, the differences in both the grain sizes and the elongations of the specimens became small, i.e., their average grain sizes were 3.2 and 3.8 μm and their elongations were 12.0% and 13.3%, respectively. For the specimens extruded at the same temperature, pre-annealing treatment obviously improved the plasticity of the alloy, which is attributed to an increase in soft texture or to grain refinement in the specimens as a result of the pre-annealing + T6 treatment.展开更多
The influence of pre-annealing on thermal stability of the amorphousZr_(70)Cu_(20)Ni_(10) alloy was reported by employing the differential scanning calorimetry (DSC)and high-resolution transmission electron microscopy...The influence of pre-annealing on thermal stability of the amorphousZr_(70)Cu_(20)Ni_(10) alloy was reported by employing the differential scanning calorimetry (DSC)and high-resolution transmission electron microscopy (HRTEM) techniques. It has been observed thatthe supercooled liquid region decreases with increasing the annealing time under isothermalconditions, indicating that the thermal stability of the amorphous Zr_(70)Cu_(20)Ni_(10) alloydecreases gradually. HRTEM observations reveal that there exist some ordered atomic clusters in theamorphous matrix at the relaxation stage. These ordered atomic clusters can be regarded asprecursors for the precipitation of the crystalline phases in the subsequent crystal-lizationprocess. The reasons resulting in the decrease in thermal stability of the amorphousZr_(70)Cu_(20)Ni_(10) alloy with annealing time are discussed through the Gaussian decomposition forthe radial distribution function of the amorphous Zr_(70)Cu_(20)Ni_(10) alloy.展开更多
The crystallization kinetics of the Cu_(40)Ti_(60) glasses,either as-quenched or pre-annealed,has been studied by differential scanning calorimetry.The crystallization temperature,activation energy for crystallization...The crystallization kinetics of the Cu_(40)Ti_(60) glasses,either as-quenched or pre-annealed,has been studied by differential scanning calorimetry.The crystallization temperature,activation energy for crystallization and Avrami exponent were found to be lowered by the pre-an- nealing.Both activation energies of nucleation and growth of the amorphous CuaoTi_(60) are ob- tained on the basis of experimental results and theoretical analysis.展开更多
To explore the temperature dependence of deformation behavior of BCC structural materials and the relevant effect of pre-annealing, commercially pure iron (CP Fe) produced by equal-channel angular pressing (ECAP) ...To explore the temperature dependence of deformation behavior of BCC structural materials and the relevant effect of pre-annealing, commercially pure iron (CP Fe) produced by equal-channel angular pressing (ECAP) is selected as the experimental material. The influences of deformation temperature T and pre-annealing on deformation behavior, surface deformation characteristics and substructures of ECAP Fe were systematically studied. The results show that ECAP Fe undergoes a remarkable strain softening stage after a rapid strain hardening during uniaxial compression, and the softening degree and the yield strength avs first decrease and then increase with raising temperature. Pre-annealing at 400 ℃ effectively weakens the strain softening degree and increases trys. To understand the influence of deformation temperature on deformation behavior, as well as the relevant pre-annealing effect, deformation and damage characteristics and dislocation structures are studied in detail. In a word, the strain softening of ECAP Fe is associated not only with internal structural instability, but also with temperature, and pre-annealing at 400 ℃ improves high-temperature me- chanical properties of ECAP Fe.展开更多
基金financially supported by the National Key Technologies R & D Program of China (No. 2016YFB0300901)
文摘Taking extruded Al–Zn–Mg–Cu alloy(7A04 alloy) bars as the research object, the effect and mechanism of pre-annealing treatments on the microstructure and mechanical properties of the aged alloy bars were investigated. The results show that a pre-annealing treatment at 350°C for 15 h before a T6 treatment substantially reduced the sensitivity of the microstructure and mechanical properties of the extruded 7A04 aluminum alloy specimens toward the extrusion temperature. The average grain sizes of the specimens extruded at 390 and 430°C after T6 treatment were 3.4 and 8.1 μm, respectively, and their elongations to failure were 7.0% and 9.2%, respectively. However, after pre-annealing + T6 treatment, the differences in both the grain sizes and the elongations of the specimens became small, i.e., their average grain sizes were 3.2 and 3.8 μm and their elongations were 12.0% and 13.3%, respectively. For the specimens extruded at the same temperature, pre-annealing treatment obviously improved the plasticity of the alloy, which is attributed to an increase in soft texture or to grain refinement in the specimens as a result of the pre-annealing + T6 treatment.
基金This work is financially supported by the National Natural Science Foundation of China (No.59871025 and 50171006),Hi-tech ResearchDevelopment Program of China(863)(No.2001AA331010)National Major Basic Research Project of China(973)(No.G2000 6720
文摘The influence of pre-annealing on thermal stability of the amorphousZr_(70)Cu_(20)Ni_(10) alloy was reported by employing the differential scanning calorimetry (DSC)and high-resolution transmission electron microscopy (HRTEM) techniques. It has been observed thatthe supercooled liquid region decreases with increasing the annealing time under isothermalconditions, indicating that the thermal stability of the amorphous Zr_(70)Cu_(20)Ni_(10) alloydecreases gradually. HRTEM observations reveal that there exist some ordered atomic clusters in theamorphous matrix at the relaxation stage. These ordered atomic clusters can be regarded asprecursors for the precipitation of the crystalline phases in the subsequent crystal-lizationprocess. The reasons resulting in the decrease in thermal stability of the amorphousZr_(70)Cu_(20)Ni_(10) alloy with annealing time are discussed through the Gaussian decomposition forthe radial distribution function of the amorphous Zr_(70)Cu_(20)Ni_(10) alloy.
文摘The crystallization kinetics of the Cu_(40)Ti_(60) glasses,either as-quenched or pre-annealed,has been studied by differential scanning calorimetry.The crystallization temperature,activation energy for crystallization and Avrami exponent were found to be lowered by the pre-an- nealing.Both activation energies of nucleation and growth of the amorphous CuaoTi_(60) are ob- tained on the basis of experimental results and theoretical analysis.
基金financially supported by the National Natural Science Foundation of China (Nos. 51231002, 51271054, 51201077 and 50671023)the Specialized Research Fund for the Doctoral Program of Higher Education of China (No. 20110042110017)the Fundamental Research Funds for the Central Universities of China (Nos. N110105001 and N120505001)
文摘To explore the temperature dependence of deformation behavior of BCC structural materials and the relevant effect of pre-annealing, commercially pure iron (CP Fe) produced by equal-channel angular pressing (ECAP) is selected as the experimental material. The influences of deformation temperature T and pre-annealing on deformation behavior, surface deformation characteristics and substructures of ECAP Fe were systematically studied. The results show that ECAP Fe undergoes a remarkable strain softening stage after a rapid strain hardening during uniaxial compression, and the softening degree and the yield strength avs first decrease and then increase with raising temperature. Pre-annealing at 400 ℃ effectively weakens the strain softening degree and increases trys. To understand the influence of deformation temperature on deformation behavior, as well as the relevant pre-annealing effect, deformation and damage characteristics and dislocation structures are studied in detail. In a word, the strain softening of ECAP Fe is associated not only with internal structural instability, but also with temperature, and pre-annealing at 400 ℃ improves high-temperature me- chanical properties of ECAP Fe.