Through microstructure observation and X-ray diffraction analysis, the equilibrium phase constituents of Al-Zn alloy that contains 2 at. pct Cu at room temperature have been determined as Al-based solid solution (α),...Through microstructure observation and X-ray diffraction analysis, the equilibrium phase constituents of Al-Zn alloy that contains 2 at. pct Cu at room temperature have been determined as Al-based solid solution (α), Zn-based solid solution and AI4Cu3Zn phase (T'-phase), which are different from a phase, Zn phase and CuZn4 phase originally believed. It is determined that the products of discontinuous precipitation transformation below 277℃ are not the equilibrium phase constituents, but the metastable phases made up of a phase, Zn phase and CuZn4 phase. The phase constituents after discontinuous precipitation of AIZn-2Cu alloy would transform to the ones in equilibrium status: Al-based solid solution (α) in fcc structure, Zn-based solid solution in hcp structure and AI4Cu3Zn phase (T'-phase) ultimately through plastic deformation at room temperature and re-heating treatment below 277℃.展开更多
The effect of Cu additions on discontinuous precipitation of AlZn alloy were studied with optical microscopy, scanning electron microscopy and X-ray diffraction. It is found that the effect of addition of 2 at. pct Cu...The effect of Cu additions on discontinuous precipitation of AlZn alloy were studied with optical microscopy, scanning electron microscopy and X-ray diffraction. It is found that the effect of addition of 2 at. pct Cu on cellular nucleation site is not remarkable, while the effect of aging temperature on cellular nucleation site of AlZn and AIZn-2Cu alloys is fairly obvious. The cell growth rate of discontinuous precipitation of AlZn alloy is remarkably accelerated with the addition of 2 at. pct Cu. The discontinuous precipitation microstructure of AlZn alloy is not apparently affected with the addition of 2 at. pct Cu and the cellular front is still fine microstructure of spinodal decomposition. The phase constituents consist of a fcc Al-rich phase, a hcp Zn-rich phase and a CuZn4 phase. The transformation rate of discontinuous precipitation of AlZn alloy is remarkably accelerated with the addition of 2 at. pct Cu.展开更多
Recrystallization of cold-rolled discontinuous, precipitation microstructurewhich has fine laminar structure in an Al-40 percent Zn (atom fraction) binary alloy is investigatedby optical microscopy, SEM and TEM. It is...Recrystallization of cold-rolled discontinuous, precipitation microstructurewhich has fine laminar structure in an Al-40 percent Zn (atom fraction) binary alloy is investigatedby optical microscopy, SEM and TEM. It is found that there are two kinds of recrystallizationmechanisms: continuous coarsening (CC) and discontinuous coarsening (DC). The latter can be dividedinto coarsening mainly driven by stored deformation energy at colony boundaries and slip bands andthe one mainly driven by boundary energy in the area with little deformation. It is shown that theaddition of Cu can retard the nucleation of coarsening cells and their growth. X-Ray diffractionanalysis indicated the metastable phase CuZn_4 transformed into equilibrium phase A;_4Cu_3Zn duringthe heating process.展开更多
The effect of Cu addition on the spinodal decomposition of the Al-Zn alloy with symmetrical compositions has been investigated by X-ray diffraction analysis. It is found that the single fcc phase can be obtained in th...The effect of Cu addition on the spinodal decomposition of the Al-Zn alloy with symmetrical compositions has been investigated by X-ray diffraction analysis. It is found that the single fcc phase can be obtained in the AlZn alloy with the addition of 2 at. pct Cu after solution treatment at 400℃ and water quenching to room temperature. The modulation structure occurs in two types of alloys aged at room temperature for 30 min. The spinodal process remarkably slows down above or at the three phase equilibrium temperature, particularly at room temperature due to the addition of 2 at. pct Cu. The spinodal time increases by 20 times when aging at 300℃ and by more than 30 times when aging at room temperature.展开更多
The coarsening mechanism and kinetics of discontinuous precipitation (DP) in Al-Zn-(Cu) alloys were studied by means of optical microscopy, scanning electron microscopy, and X-ray diffraction analysis. The results sho...The coarsening mechanism and kinetics of discontinuous precipitation (DP) in Al-Zn-(Cu) alloys were studied by means of optical microscopy, scanning electron microscopy, and X-ray diffraction analysis. The results show that the coarsening mechanism is different as the aging temperature varies. At a low temperature (150℃), the coarsening occurs through the dissolution and spheroidization of fine laminar structure of DP; at high temperatures (above 200℃), the discontinuous coarsening (DC) of DP microstructure mainly occurs, forming coarsening cells with a larger laminar distance. The growth velocity of coarsening cells rapidly reaches the maximum, and then decreases with the increase of time. The coarsening velocity of DP microstructure decreases due to the addition of Cu element.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
文摘Through microstructure observation and X-ray diffraction analysis, the equilibrium phase constituents of Al-Zn alloy that contains 2 at. pct Cu at room temperature have been determined as Al-based solid solution (α), Zn-based solid solution and AI4Cu3Zn phase (T'-phase), which are different from a phase, Zn phase and CuZn4 phase originally believed. It is determined that the products of discontinuous precipitation transformation below 277℃ are not the equilibrium phase constituents, but the metastable phases made up of a phase, Zn phase and CuZn4 phase. The phase constituents after discontinuous precipitation of AIZn-2Cu alloy would transform to the ones in equilibrium status: Al-based solid solution (α) in fcc structure, Zn-based solid solution in hcp structure and AI4Cu3Zn phase (T'-phase) ultimately through plastic deformation at room temperature and re-heating treatment below 277℃.
基金This work was financially supported by the National Natural Science Foundation of China under No.59971015.We are grateful to Prof.H.Ding for discussion and proof in English.
文摘The effect of Cu additions on discontinuous precipitation of AlZn alloy were studied with optical microscopy, scanning electron microscopy and X-ray diffraction. It is found that the effect of addition of 2 at. pct Cu on cellular nucleation site is not remarkable, while the effect of aging temperature on cellular nucleation site of AlZn and AIZn-2Cu alloys is fairly obvious. The cell growth rate of discontinuous precipitation of AlZn alloy is remarkably accelerated with the addition of 2 at. pct Cu. The discontinuous precipitation microstructure of AlZn alloy is not apparently affected with the addition of 2 at. pct Cu and the cellular front is still fine microstructure of spinodal decomposition. The phase constituents consist of a fcc Al-rich phase, a hcp Zn-rich phase and a CuZn4 phase. The transformation rate of discontinuous precipitation of AlZn alloy is remarkably accelerated with the addition of 2 at. pct Cu.
文摘Recrystallization of cold-rolled discontinuous, precipitation microstructurewhich has fine laminar structure in an Al-40 percent Zn (atom fraction) binary alloy is investigatedby optical microscopy, SEM and TEM. It is found that there are two kinds of recrystallizationmechanisms: continuous coarsening (CC) and discontinuous coarsening (DC). The latter can be dividedinto coarsening mainly driven by stored deformation energy at colony boundaries and slip bands andthe one mainly driven by boundary energy in the area with little deformation. It is shown that theaddition of Cu can retard the nucleation of coarsening cells and their growth. X-Ray diffractionanalysis indicated the metastable phase CuZn_4 transformed into equilibrium phase A;_4Cu_3Zn duringthe heating process.
基金supported by the National Natural Science Foundation of China under grant No.59971015supported by the Laboratory of Atom Imaging of Solids,Institute of Metal Research,the Chinese Academy of Sciences.
文摘The effect of Cu addition on the spinodal decomposition of the Al-Zn alloy with symmetrical compositions has been investigated by X-ray diffraction analysis. It is found that the single fcc phase can be obtained in the AlZn alloy with the addition of 2 at. pct Cu after solution treatment at 400℃ and water quenching to room temperature. The modulation structure occurs in two types of alloys aged at room temperature for 30 min. The spinodal process remarkably slows down above or at the three phase equilibrium temperature, particularly at room temperature due to the addition of 2 at. pct Cu. The spinodal time increases by 20 times when aging at 300℃ and by more than 30 times when aging at room temperature.
文摘The coarsening mechanism and kinetics of discontinuous precipitation (DP) in Al-Zn-(Cu) alloys were studied by means of optical microscopy, scanning electron microscopy, and X-ray diffraction analysis. The results show that the coarsening mechanism is different as the aging temperature varies. At a low temperature (150℃), the coarsening occurs through the dissolution and spheroidization of fine laminar structure of DP; at high temperatures (above 200℃), the discontinuous coarsening (DC) of DP microstructure mainly occurs, forming coarsening cells with a larger laminar distance. The growth velocity of coarsening cells rapidly reaches the maximum, and then decreases with the increase of time. The coarsening velocity of DP microstructure decreases due to the addition of Cu element.
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.
