A new high throughput heat-treatment method with a continuous temperature gradient between 600 and 700 ？C was utilized on the Ti-5553 alloy（Ti-5 Al-5 Mo-5 V-3 Cr, mass fraction, %）. The temperature gradient was ind...A new high throughput heat-treatment method with a continuous temperature gradient between 600 and 700 ？C was utilized on the Ti-5553 alloy（Ti-5 Al-5 Mo-5 V-3 Cr, mass fraction, %）. The temperature gradient was induced by the variation of the axial section of sample, which was heated by the direct current. The variation of continuous cooling rates on the treated sample was realized by using the end quenching method. The microstructural evolution and mechanical properties under different heat treatment conditions were evaluated. The results show that the pseudo-spinodal decomposition of the alloy occurs at（617±1） ？C, and the size of the precipitated α phase is around 300 nm. Moreover, the highest microhardness is obtained after the heat treatment at the pseudo-spinodal decomposition temperature for 4 h. These indicate that the high throughput method is efficient and fast to determine the phase transformation temperature and corresponding microstructural evolution of alloys.展开更多
Cu-15Ni-8Sn-0.3Nb alloy rods were prepared by means of powder metallurgy followed by hot extrusion.Element maps obtained by electron probe micro analyzer(EPMA)showed that Nb-rich phases were formed and distributed wit...Cu-15Ni-8Sn-0.3Nb alloy rods were prepared by means of powder metallurgy followed by hot extrusion.Element maps obtained by electron probe micro analyzer(EPMA)showed that Nb-rich phases were formed and distributed within grains and at grain boundaries of the Cu-15Ni-8Sn-0.3Nb alloy.Transmission electron microscope(TEM)results indicated that there was no obvious orientation relationship between these phases and the matrix.Spinodal decomposition and ordering transformation appeared at early stages of aging at400°C and caused significant strengthening.Cu-15Ni-8Sn-0.3Nb alloy exhibited both higher strength(ultimate tensile strength>1030MPa)and higher tensile ductility(elongation>9.1%)than Cu-15Ni-8Sn alloy after aging treatment.The improvement was caused by Nb-rich phases at grain boundaries which led o the refinement of grain size and postponed the growth of discontinuous precipitates during aging.展开更多
In order to investigate the formation mechanisms of the layered growth phenomena in diffusion couples with spinodal decomposition,a phase field model combined with elastic strain field was employed.Microstructure evol...In order to investigate the formation mechanisms of the layered growth phenomena in diffusion couples with spinodal decomposition,a phase field model combined with elastic strain field was employed.Microstructure evolutions of diffusion couple with spinodal decomposition in binary alloys were numerically simulated by considering concentration fluctuation and elastic anisotropy.The simulation results indicate that the number of the periodical layers decreases with the increase of initial concentration fluctuation,even with large elastic anisotropy.The growth of layered microstructures can be attributed to the directional diffusion enhanced by initially discontinuous chemical potential at the interface.展开更多
基金Project(2014CB644002)supported by the National Basic Research and Development Project of ChinaProject(2015CX004)supported by the Innovation-driven Plan in Central South University,China
文摘A new high throughput heat-treatment method with a continuous temperature gradient between 600 and 700 ？C was utilized on the Ti-5553 alloy（Ti-5 Al-5 Mo-5 V-3 Cr, mass fraction, %）. The temperature gradient was induced by the variation of the axial section of sample, which was heated by the direct current. The variation of continuous cooling rates on the treated sample was realized by using the end quenching method. The microstructural evolution and mechanical properties under different heat treatment conditions were evaluated. The results show that the pseudo-spinodal decomposition of the alloy occurs at（617±1） ？C, and the size of the precipitated α phase is around 300 nm. Moreover, the highest microhardness is obtained after the heat treatment at the pseudo-spinodal decomposition temperature for 4 h. These indicate that the high throughput method is efficient and fast to determine the phase transformation temperature and corresponding microstructural evolution of alloys.
基金Project (2016YFB0301400) supported by the National Key Research and Development Program of ChinaProject (9140A12040515QT48167) supported by the Pre-research Fund of the General Armaments Department of ChinaProject (CSU20151024) supported by the Innovation-driven Plan of Central South University,China
文摘Cu-15Ni-8Sn-0.3Nb alloy rods were prepared by means of powder metallurgy followed by hot extrusion.Element maps obtained by electron probe micro analyzer(EPMA)showed that Nb-rich phases were formed and distributed within grains and at grain boundaries of the Cu-15Ni-8Sn-0.3Nb alloy.Transmission electron microscope(TEM)results indicated that there was no obvious orientation relationship between these phases and the matrix.Spinodal decomposition and ordering transformation appeared at early stages of aging at400°C and caused significant strengthening.Cu-15Ni-8Sn-0.3Nb alloy exhibited both higher strength(ultimate tensile strength>1030MPa)and higher tensile ductility(elongation>9.1%)than Cu-15Ni-8Sn alloy after aging treatment.The improvement was caused by Nb-rich phases at grain boundaries which led o the refinement of grain size and postponed the growth of discontinuous precipitates during aging.
基金Project(2017YFB0702401) supported by the National Key R&D Program of ChinaProject(51301146) supported by the National Natural Science Foundation of ChinaProjects(20720170038,20720170048) supported by the Fundamental Research Funds for the Central Universities,China
文摘In order to investigate the formation mechanisms of the layered growth phenomena in diffusion couples with spinodal decomposition,a phase field model combined with elastic strain field was employed.Microstructure evolutions of diffusion couple with spinodal decomposition in binary alloys were numerically simulated by considering concentration fluctuation and elastic anisotropy.The simulation results indicate that the number of the periodical layers decreases with the increase of initial concentration fluctuation,even with large elastic anisotropy.The growth of layered microstructures can be attributed to the directional diffusion enhanced by initially discontinuous chemical potential at the interface.
