Quantification of Hierarchal Microstructures of Metallic Materials and the Prediction of the strength by Homogenization Method

材料的微观结构变化是多组分相互作用的结果。在金属材料中，性能是利用显微组织的不均匀性来设计的。本研究的目的是定量地阐明非均匀组织的组织演变，并估计耐热金属材料表现出复杂的多相层次结构的性能变化。为了实现这些目的，我们采用了“系统自由能”的概念，并用这个概念量化了微观组织变化的程度，这种量化使得获得组织演变与材料强度变化之间的关系成为可能。例如，用相场方法模拟了镍基高温合金从形成到崩溃的一系列微观组织演变，并将结果考虑到对蠕变强度…的理解更多的合金。结果表明，随着蠕变时间的延长，蠕变应变增大，本征应变的对称性由立方转变为四方。结果表明，通过改变结构的稳定方向，形成的垂直于伽马质相[001]方向的木筏结构呈波浪形。木筏结构稳定性的变化与高温合金的蠕变强度密切相关，即当木筏结构稳定时，蠕变强度保持较高。此外，还发现蠕变应变能够从排架结构的形状中推断出来。得出了铁素体耐热钢蠕变强度与层状组织之间的关系，即马氏体相板条、块状和包状组织的稳定性与其长期蠕变强度直接相关。合金元素对层状组织稳定性的影响由三元系扩散实验得到的交叉扩散系数来解释。在三元体系中，通过扩散实验得到了四个互扩散系数，并且发现母材中合金元素之间的相互作用是两个互扩散系数的符号。较少

Microstructural changes of materials axe emerged as a result of interactions of multi-Sixes in it. In metallic materials, the properties have been designed by using the inhomogeneousity of the microstructure The purposes of this study are to elucidate quantitatively the microstructural evolution of the inhomogeneous microstructure and to estimate the change of properties of heat resistant metallic materials, which show a complex hierarchy multi-phase. In order to perform these purposes, we employed the concept of “System Free Energy" and quantified the degree of the microstructural change using the concept This quantification made it possible to obtain the relationship between the microstructural al evolution and the strength change of the materials For example, a series of microstructural evolution from the formation to collapse the rafted structure in nickel-based superalloys was simulated by the Phase-field method, and the results were considered for understanding the creep strength … More of the alloys. It was found that the symmetry of the eigen strain changed from cubic to tetragonal as a result of the increase of the creep strain with increasing creep time. As a result the rafted structure formed perpendicular to [001] direction of the gamma-prime phase became wavy shape by changing the stable direction of the structure. The change in the stability of the rafted structure was strongly related to the creep strength of the superalloys, i.e. the creep strength was kept high when the rafted structure was stable. Furthermore, it was found that the creep strain was able to deduce from the shape of the rafted structures. The relationship between the creep strength and the hierarchal microstructure of ferritic heat resistant steels was also obtained, i.e., the stability of the lath, block and packet of the martensite phase was directly related to the long-term creep strength of them.The effects of alloying elements on the stability of the hierarchal microstructures were elucidated by the c cross-interdiffusion coefficients obtained from a series of diffusion experiments using ternary systems. In ternary systems, four interdiffusion coefficients were obtained by the diffusion experiments, and the interactions between the alloying elements in the host metal were emerged as the sign of two cross interdiffusion coefficients. Less