The aim of the present work is to develop a model for simulating double-peak precipitation hardening kinetics in Al-Zn-Mg alloy with the simultaneous formation of different types of precipitates at elevated temperatur...The aim of the present work is to develop a model for simulating double-peak precipitation hardening kinetics in Al-Zn-Mg alloy with the simultaneous formation of different types of precipitates at elevated temperatures based on the modified Langer-Schwartz approach. The double aging peaks are present in the long time age-hardening curves of Al-Zn-Mg alloys. The physically-based model, while taking explicitly into account nucleation, growth, coarsening of the new phase precipitations and two strengthening mechanisms associated with particle-dislocation interaction （shearing and bypassing）, was used for the analysis of precipitates evolution and precipitation hardening during aging of Al-Zn-Mg alloy. Model predictions were compared with the measurements of Al-Zn-Mg alloy. The systematic and quantitative results show that the predicted hardness profiles of double peaks via adding a shape dependent parameter in the growth equation for growth and coarsening generally agree well with the measured ones. Two strengthening mechanisms associated with particle-dislocation interaction （shearing and bypassing） were considered operating simultaneously in view of the particle size-distribution. The transition from shearing to bypassing strengthening mechanism was found to occur at rather early stage of the particle growth. The bypassing was found to be the prevailing strengthening mechanism in the investigated alloys.展开更多
Effects of Mg content on the microstructure and mechanical properties of low Zn-containing Al−xMg−3Zn−1Cu cast alloys(x=3−5,wt.%)were investigated.As Mg content increased in the as-cast alloys,the grains were refined ...Effects of Mg content on the microstructure and mechanical properties of low Zn-containing Al−xMg−3Zn−1Cu cast alloys(x=3−5,wt.%)were investigated.As Mg content increased in the as-cast alloys,the grains were refined due to enhanced growth restriction,and the formation ofη-Mg(AlZnCu)_(2) and S-Al_(2)CuMg phases was inhibited while the formation of T-Mg_(32)(AlZnCu)_(49 )phase was promoted when Mg content exceeded 4 wt.%.The increase of Mg content encumbered the solution kinetics by increasing the size of eutectic phase but accelerated and enhanced the age-hardening through expediting precipitation kinetics and elevating the number density of the precipitates.As Mg content increased,the yield strength and tensile strength of the as-cast,solution-treated and peak-aged alloys were severally improved,while the elongation of the alloys decreased.The tensile strength and elongation of the peak-aged Al−5Mg−3Zn−1Cu alloy exceed 500 MPa and 5%,respectively.Precipitation strengthening implemented by T′precipitates is the predominant strengthening mechanism in the peak-aged alloys and is enhanced by increasing Mg content.展开更多
AM50-4%(Zn,Y)alloy with a Zn/Y mole ratio of6:1was subjected to thermal analysis,and the results were used for designing a two-step progressive solution treatment process.The effects of solution and aging treatments o...AM50-4%(Zn,Y)alloy with a Zn/Y mole ratio of6:1was subjected to thermal analysis,and the results were used for designing a two-step progressive solution treatment process.The effects of solution and aging treatments on the microstructure and mechanical properties of the AM50-4%(Zn,Y)alloy were investigated using OM,XRD,SEM/EDS,TEM,tensile test and hardness test.The experimental results demonstrated that the two-step progressive solution treatment could make theΦandβphases sufficiently dissolve into the matrix which possessed higher supersaturated degree of the dissolved solute compared with the one-step solution treatment.This resulted in a certain enhancement of the precipitation strengthening effect during the subsequent aging process.The precipitation of theФphase had a greater impact on the comprehensive mechanical properties of the alloy thanβphase precipitation when the aging treatment was performed at180℃.The peak aging strength of the AM50-4%(Zn,Y)alloy which was subjected to the two-step progressive solution treatment process(345℃for16h and375℃for6h)was obtained after the aging treatment at180℃for12h.展开更多
基金Project(51021063)supported by the Creative Research Group of the National Natural Science Foundation of ChinaProject(50831007)supported by the National Natural Science Foundation of China+1 种基金Project(2011CB610401)supported by the National Basic Research Program of ChinaProject(12C1142)supported by the Education Department of Hunan Province,China
文摘The aim of the present work is to develop a model for simulating double-peak precipitation hardening kinetics in Al-Zn-Mg alloy with the simultaneous formation of different types of precipitates at elevated temperatures based on the modified Langer-Schwartz approach. The double aging peaks are present in the long time age-hardening curves of Al-Zn-Mg alloys. The physically-based model, while taking explicitly into account nucleation, growth, coarsening of the new phase precipitations and two strengthening mechanisms associated with particle-dislocation interaction （shearing and bypassing）, was used for the analysis of precipitates evolution and precipitation hardening during aging of Al-Zn-Mg alloy. Model predictions were compared with the measurements of Al-Zn-Mg alloy. The systematic and quantitative results show that the predicted hardness profiles of double peaks via adding a shape dependent parameter in the growth equation for growth and coarsening generally agree well with the measured ones. Two strengthening mechanisms associated with particle-dislocation interaction （shearing and bypassing） were considered operating simultaneously in view of the particle size-distribution. The transition from shearing to bypassing strengthening mechanism was found to occur at rather early stage of the particle growth. The bypassing was found to be the prevailing strengthening mechanism in the investigated alloys.
基金supported by the National Natural Science Foundation of China (Nos. 51674166, U1902220)the National Key R&D Program of China (No. 2021YFB3701303)。
文摘Effects of Mg content on the microstructure and mechanical properties of low Zn-containing Al−xMg−3Zn−1Cu cast alloys(x=3−5,wt.%)were investigated.As Mg content increased in the as-cast alloys,the grains were refined due to enhanced growth restriction,and the formation ofη-Mg(AlZnCu)_(2) and S-Al_(2)CuMg phases was inhibited while the formation of T-Mg_(32)(AlZnCu)_(49 )phase was promoted when Mg content exceeded 4 wt.%.The increase of Mg content encumbered the solution kinetics by increasing the size of eutectic phase but accelerated and enhanced the age-hardening through expediting precipitation kinetics and elevating the number density of the precipitates.As Mg content increased,the yield strength and tensile strength of the as-cast,solution-treated and peak-aged alloys were severally improved,while the elongation of the alloys decreased.The tensile strength and elongation of the peak-aged Al−5Mg−3Zn−1Cu alloy exceed 500 MPa and 5%,respectively.Precipitation strengthening implemented by T′precipitates is the predominant strengthening mechanism in the peak-aged alloys and is enhanced by increasing Mg content.
基金Project (201602548) supported by Liaoning Province Natural Science Foundation,ChinaProject (1711800) supported by Shenyang Science and Technology Plan,China+1 种基金Project (LQGD2017032) supported by Youth Project of Liaoning Education Department,ChinaProjects (51504153,51571145) supported by the National Natural Science Foundation of China
文摘AM50-4%(Zn,Y)alloy with a Zn/Y mole ratio of6:1was subjected to thermal analysis,and the results were used for designing a two-step progressive solution treatment process.The effects of solution and aging treatments on the microstructure and mechanical properties of the AM50-4%(Zn,Y)alloy were investigated using OM,XRD,SEM/EDS,TEM,tensile test and hardness test.The experimental results demonstrated that the two-step progressive solution treatment could make theΦandβphases sufficiently dissolve into the matrix which possessed higher supersaturated degree of the dissolved solute compared with the one-step solution treatment.This resulted in a certain enhancement of the precipitation strengthening effect during the subsequent aging process.The precipitation of theФphase had a greater impact on the comprehensive mechanical properties of the alloy thanβphase precipitation when the aging treatment was performed at180℃.The peak aging strength of the AM50-4%(Zn,Y)alloy which was subjected to the two-step progressive solution treatment process(345℃for16h and375℃for6h)was obtained after the aging treatment at180℃for12h.
