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| 1 | Numerical simulation of precipitation kinetics in multicomponent alloys显示文摘A universal numerical model based on the particle size distribution(PSD)approach has been developed for the simulation of precipitation kinetics in multicomponent alloys during isothermal ageing.Nucleation was implemented utilizing the classical nucleation theory(CNT).Growth and coarsening were modeled by a single growth kinetics equation,which is constructed based on the interfacial diffusion flux balance and the capillarity effect.Only partial off-diagonal terms in the diffusion matrix(diffusion of individual components in the matrix)were taken into account in the calculations to minimize the computational cost while coupling with CALPHAD to extract thermodynamics equilibrium around the interface.A new feature of the model is the incorporation of a more realistic spatial site distribution via a Voronoi construction in the characteristic cell,for the purpose of modifying the diffusion distance.Computational predictions of the precipitate dimensions and the precipitation kinetics were compared with the atom probe tomography(APT)measurements on ternary Ni-Al-Cr alloys isothermally aged at 873 K.It is found that the temporal evolution of the dimensions and composition of the precipitates is well captured,as is the dependence on changes in the alloy composition.The new modification with Voronoi construction demonstrates that the overall precipitation kinetics depends on the density and the spatial site distribution of precipitates.The ability to handle sophisticated alloy chemistries by quantitative equations,the compositional sensitivity of microstructural characteristics emerging from the simulation results,and the ability to visualize the spatial distribution of precipitates make the work very promising for multicomponent alloy design and optimization. | K.Xu J.D.Liu S.van der Zwaag W.Xu J.G.Li | 2022 | Journal of Materials Science & Technology2022，，33： | 1 |
| 2 | Misorientation dependent thermal condition-solute field cooperative effect on competitive grain growth in the converging case during directional solidification of a nickel-base superalloy显示文摘Nowadays,thermal condition and solute field are considered as the potential dominant factors controlling competitive grain growth during directional solidification process.However,the controlling modes and critical conditions of competitive grain growth have been drastically debated over the past two decades.In this work,thermal condition and solute field are combined to study the competitive grain growth in the converging case by experimental observation and numerical simulation of bicrystal samples.We find the competitive grain growth is controlled by the cooperative effect of thermal condition and solute field,and the controlling modes are related to the bicrystal misorientation between favorably and unfavorably oriented grains.When the unfavorably oriented grain is low misoriented,unfavorably oriented grain dominates grain selection,and the competitive grain growth performs as solute field domination.However,with the increase of unfavorably oriented grain’s misorientation,the grain selection converts into favorably oriented grain domination,and the competitive grain growth changes to thermal condition domination.To explain these abnormal transformation phenomena,we propose a misorientation dependent thermal condition-solute field cooperative domination model and identify the critical conditions by a critical misorientation(θ_(cm)).According to dynamic equation of dendrite growth,we calculate the critical misorientationθ;to prove this model.The theoretical calculation results agree well with the experimental results. | X.B.Meng J.G.Li C.N.Jing J.D.Liu S.Y.Ma J.J.Liang C.W.Zhang M.Wang B.T.Tang T.Lin J.L.Chen X.L.Zhang Q.Li | 2022 | Journal of Materials Science & Technology2022，，1： | 1 |
| 3 | Stress-rupture behavior of a Re-containing Ni-base single crystal superalloy at high temperatures显示文摘A Re-containing Ni-base single crystal superalloy was used to investigate the elementary processes associated with stress-rupture behavior at different temperatures where theγʹrafting occurs.At 900°C,the rupture behavior is mainly determined by the multiplication of dislocations within the wideningγchannels,which is closely linked with the propagation of microcracks along the inherentγ/γʹinterfaces.The rapid formation of lamellaγ/γʹraft structure,along with the developed-well interfacial dislocation networks,and its elastic instability are primarily responsible for the rupture behavior at 1100°C.There is a clear curvature tendency in the Larson-Miller plot of stress-rupture lifetime in relation to stress at high temperatures.It indicates that the influence extent ofγʹrafting on stress-rupture behavior is sensitive to the acting conditions of temperature and stress. | G.L.Wang D.Q.Qi J.L.Liu J.D.Liu J.G.Li Y.Z.Zhou X.F.Sun | 2023 | Journal of Materials Science & Technology2023，，32： | 0 |
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