This study investigated the influence of graded Zn content on the evolution of precipitated and iron-rich phases and grain struc-ture of the alloys,designed and developed the Al–8.0Zn–1.5Mg–1.5Cu–0.2Fe(wt%)alloy w...This study investigated the influence of graded Zn content on the evolution of precipitated and iron-rich phases and grain struc-ture of the alloys,designed and developed the Al–8.0Zn–1.5Mg–1.5Cu–0.2Fe(wt%)alloy with high strength and formability.With the increase of Zn content,forming the coupling distribution of multiscale precipitates and iron-rich phases with a reasonable matching ratio and dispersion distribution characteristics is easy.This phenomenon induces the formation of cell-like structures with alternate distribu-tion of coarse and fine grains,and the average plasticity–strain ratio(characterizing the formability)of the pre-aged alloy with a high strength is up to 0.708.Results reveal the evolution and influence mechanisms of multiscale second-phase particles and the corresponding high formability mechanism of the alloys.The developed coupling control process exhibits considerable potential,revealing remarkable improvements in the room temperature formability of high-strength Al–Zn–Mg–Cu alloys.展开更多
Three kinds of Al-Zn-Mg-Cu based alloys with 0.22%, 0.36%(Sc+Zr) (mass fraction, %), and without Sc, Zr addition were prepared by ingot metallurgy. By using optical microscopy, transmission electronic microscopy and s...Three kinds of Al-Zn-Mg-Cu based alloys with 0.22%, 0.36%(Sc+Zr) (mass fraction, %), and without Sc, Zr addition were prepared by ingot metallurgy. By using optical microscopy, transmission electronic microscopy and scanning electron microscopy, the effects of microalloying elements of Sc, Zr on the microstructure of super-high-strength Al-Zn-Mg-Cu alloys related to mechanical properties were investigated. The tensile properties and microstructures of the studied alloys under different heat treatment conditions were studied. The addition of minor Sc, Zr results in the formation of Al3(Sc,Zr) particles. These particles are highly effective in refining the microstructures, retarding recrystallization, pinning dislocations and subboundaries. The strength of Al-Zn-Mg-Cu alloys was greatly improved by simultaneously adding minor Sc, Zr, meanwhile the ductility of the studied alloys remains at a higher level. The 0.36%(Sc+Zr) alloys gain the optimal properties after 465 ℃/h solution and 120 ℃/24 h aging. The increment of strength is mainly due to strengthening of fine grain and substructure and precipitation of Al3(Sc, Zr) particles.展开更多
A series of Al-8.2Zn-2.1Mg-2.3Cu based as-cast alloys and some plates with thickness of 4 mm containing minor Sc and Zr were prepared. The effect of joint addition of minor Sc and Zr on microstructure and mechanical p...A series of Al-8.2Zn-2.1Mg-2.3Cu based as-cast alloys and some plates with thickness of 4 mm containing minor Sc and Zr were prepared. The effect of joint addition of minor Sc and Zr on microstructure and mechanical properties of Al-Zn-Mg-Cu alloys were investigated by using OM, SEM with EDS and TEM. The results show that by adding 0.18% Zr (mass fraction) in the cast alloy, the grains can be refined to a certain degree, and by adding 0.18% Sc a little as well. Adding Sc and Zr can generate strong grain refinement effect and obtain a fine equiaxed grain structure, because primary Al3(ScxZr1- )precipitation forms in front of the x a-Al grains. The microstructure and tensile test results show that 0.18% addition of Zr does not bring higher tensile strength and elongation to the alloy of adding Sc, but a better inhibition to recrystallization. Recrystallization inhibiting effect is the strongest in the alloys with joint addition of Sc and Zr. When the content of Zr is unchanged, the strength and elongation of the alloys increase with increasing Sc addition. The increase of strength and elongation in the alloys is related to the refine grain strengthening, precipitation particles strengthening and substructure strengthening principles.展开更多
The mechanical properties and stress corrosion cracking (SCC) resistance of an Al-Zn-Cu-Mg-Sc-Zr alloy under different aging conditions were investigated. The dependence of microstructure and mechanical properties on ...The mechanical properties and stress corrosion cracking (SCC) resistance of an Al-Zn-Cu-Mg-Sc-Zr alloy under different aging conditions were investigated. The dependence of microstructure and mechanical properties on aging parameters was evaluated by tensile test, hardness test and conductivity measurement. The results show that for the alloys with retrogression and re-aging treatment (RRA), the conductivity increases with the retrogression time and temperature, while the tensile strength decreases. The transmission electron microscopy (TEM) results show that the precipitates η(MgZn2) at grain boundary aggregate apparently with retrogression time and the precipitates inside the matrix exhibit the similar distribution to T6 temper, which comprises fine GP zones, large η′(MgZn2) and η(MgZn2) phases. According to the mechanical properties and microstructure observations, the optimal RRA regime is recommended to be 120 °C, 24 h + 180 °C, 30 min + 120 °C, 24 h. The strength level of the alloy after the optimum RRA treatment is similar to that in T6 condition and the SCC resistance is improved obviously in contrast to T6 condition.展开更多
The effects of yttrium addition on microstructure and mechanical properties of as-cast Mg-6Zn-3Cu-0.6Zr-xY(x=0,0.5, 1.0,1.5 and 2.0,mass fraction,%)(ZCK630+xY for short in this study)alloys were investigated by means ...The effects of yttrium addition on microstructure and mechanical properties of as-cast Mg-6Zn-3Cu-0.6Zr-xY(x=0,0.5, 1.0,1.5 and 2.0,mass fraction,%)(ZCK630+xY for short in this study)alloys were investigated by means of OM,XRD and SEM. The results show that the average grain size of Mg-Zn-Cu-Zr magnesium alloy is effectively reduced(from 57μm to 39μm)by Y addition.The analysis of XRD indicates the existence of I-phase(Mg3Zn6Y)and W-phase(Mg3Zn3Y2)in ZCK630 alloys with Y addition.The ultimate tensile strength of ZCK630 alloys is significantly deteriorated with increasing Y addition,which is possibly related to the continuous networks of intergranular phases and the increase of W-phase.展开更多
基金supported by the National Key Research and Development Program of China(No.2021YFE0115900)the National Natural Science Foundation of China(Nos.52371016,51871029,and 51571023)the Opening Project of State Key Laboratory for Advanced Metals and Materials(Nos.2020-ZD02 and No.2022-Z03).
文摘This study investigated the influence of graded Zn content on the evolution of precipitated and iron-rich phases and grain struc-ture of the alloys,designed and developed the Al–8.0Zn–1.5Mg–1.5Cu–0.2Fe(wt%)alloy with high strength and formability.With the increase of Zn content,forming the coupling distribution of multiscale precipitates and iron-rich phases with a reasonable matching ratio and dispersion distribution characteristics is easy.This phenomenon induces the formation of cell-like structures with alternate distribu-tion of coarse and fine grains,and the average plasticity–strain ratio(characterizing the formability)of the pre-aged alloy with a high strength is up to 0.708.Results reveal the evolution and influence mechanisms of multiscale second-phase particles and the corresponding high formability mechanism of the alloys.The developed coupling control process exhibits considerable potential,revealing remarkable improvements in the room temperature formability of high-strength Al–Zn–Mg–Cu alloys.
基金financially supported by the National Key Research and Development Program of China(No.2020YFB0311201)the National Natural Science Foundation of China(No.51627802)。
基金Project(2002AA305104) supported by the National High-Tech Research and Development Program of China
文摘Three kinds of Al-Zn-Mg-Cu based alloys with 0.22%, 0.36%(Sc+Zr) (mass fraction, %), and without Sc, Zr addition were prepared by ingot metallurgy. By using optical microscopy, transmission electronic microscopy and scanning electron microscopy, the effects of microalloying elements of Sc, Zr on the microstructure of super-high-strength Al-Zn-Mg-Cu alloys related to mechanical properties were investigated. The tensile properties and microstructures of the studied alloys under different heat treatment conditions were studied. The addition of minor Sc, Zr results in the formation of Al3(Sc,Zr) particles. These particles are highly effective in refining the microstructures, retarding recrystallization, pinning dislocations and subboundaries. The strength of Al-Zn-Mg-Cu alloys was greatly improved by simultaneously adding minor Sc, Zr, meanwhile the ductility of the studied alloys remains at a higher level. The 0.36%(Sc+Zr) alloys gain the optimal properties after 465 ℃/h solution and 120 ℃/24 h aging. The increment of strength is mainly due to strengthening of fine grain and substructure and precipitation of Al3(Sc, Zr) particles.
基金Project(2005CB623706) supported by the National Advanced Technology Research and Development Committee of China
文摘A series of Al-8.2Zn-2.1Mg-2.3Cu based as-cast alloys and some plates with thickness of 4 mm containing minor Sc and Zr were prepared. The effect of joint addition of minor Sc and Zr on microstructure and mechanical properties of Al-Zn-Mg-Cu alloys were investigated by using OM, SEM with EDS and TEM. The results show that by adding 0.18% Zr (mass fraction) in the cast alloy, the grains can be refined to a certain degree, and by adding 0.18% Sc a little as well. Adding Sc and Zr can generate strong grain refinement effect and obtain a fine equiaxed grain structure, because primary Al3(ScxZr1- )precipitation forms in front of the x a-Al grains. The microstructure and tensile test results show that 0.18% addition of Zr does not bring higher tensile strength and elongation to the alloy of adding Sc, but a better inhibition to recrystallization. Recrystallization inhibiting effect is the strongest in the alloys with joint addition of Sc and Zr. When the content of Zr is unchanged, the strength and elongation of the alloys increase with increasing Sc addition. The increase of strength and elongation in the alloys is related to the refine grain strengthening, precipitation particles strengthening and substructure strengthening principles.
基金Project(2006AA03Z523) supported by the National High-tech Research and Development Program of China
文摘The mechanical properties and stress corrosion cracking (SCC) resistance of an Al-Zn-Cu-Mg-Sc-Zr alloy under different aging conditions were investigated. The dependence of microstructure and mechanical properties on aging parameters was evaluated by tensile test, hardness test and conductivity measurement. The results show that for the alloys with retrogression and re-aging treatment (RRA), the conductivity increases with the retrogression time and temperature, while the tensile strength decreases. The transmission electron microscopy (TEM) results show that the precipitates η(MgZn2) at grain boundary aggregate apparently with retrogression time and the precipitates inside the matrix exhibit the similar distribution to T6 temper, which comprises fine GP zones, large η′(MgZn2) and η(MgZn2) phases. According to the mechanical properties and microstructure observations, the optimal RRA regime is recommended to be 120 °C, 24 h + 180 °C, 30 min + 120 °C, 24 h. The strength level of the alloy after the optimum RRA treatment is similar to that in T6 condition and the SCC resistance is improved obviously in contrast to T6 condition.
基金Project(50875031) supported by the National Natural Science Foundation of ChinaProject(2009AA03Z525) supported by the National High-tech Research and Development Program of China+1 种基金Project(20095263005) supported by Aviation Science Foundation of ChinaProject(2006) supported by the Foundation for the Young Scholars of Dalian University of Technology
文摘The effects of yttrium addition on microstructure and mechanical properties of as-cast Mg-6Zn-3Cu-0.6Zr-xY(x=0,0.5, 1.0,1.5 and 2.0,mass fraction,%)(ZCK630+xY for short in this study)alloys were investigated by means of OM,XRD and SEM. The results show that the average grain size of Mg-Zn-Cu-Zr magnesium alloy is effectively reduced(from 57μm to 39μm)by Y addition.The analysis of XRD indicates the existence of I-phase(Mg3Zn6Y)and W-phase(Mg3Zn3Y2)in ZCK630 alloys with Y addition.The ultimate tensile strength of ZCK630 alloys is significantly deteriorated with increasing Y addition,which is possibly related to the continuous networks of intergranular phases and the increase of W-phase.
