Engineering Commons^™

Computational And Experimental Study Of Structure-Property Relationships In Nial Precipitate-Strengthened Ferritic Superalloys, Shenyan Huang

Doctoral Dissertations

Ferritic superalloys strengthened by coherent ordered NiAl B2-type precipitates are promising candidates for ultra-supercritical steam-turbine applications, due to their superior resistance to creep, coarsening, oxidation, and steam corrosion as compared to Cr ferritic steels at high temperatures. Combined computational and experimental tools have been employed to investigate the interrelationships among the composition, microstructure, and mechanical behavior, and provide insight into deformation micromechanisms at elevated temperatures.

Self and impurity diffusivities in a body-centered-cubic (bcc) iron are calculated using first-principles methods. Calculated self and impurity diffusivities compare favorably with experimental measurements in both ferromagnetic and paramagnetic states of bcc Fe. The calculated …

Micromechanical Studies Of Intergranular Strain And Lattice Misorientation Fields And Comparisons To Advanced Diffraction Measurements, Lili Zheng

Doctoral Dissertations

Inhomogeneous deformation fields arising from the grain-grain interactions in polycrystalline materials have been evaluated using a crystal plasticity finite element method and extensively compared to neutron diffraction measurements under fatigue crack growth conditions. The roles of intergranular deformation anisotropy, grain boundary damage, and non-common deformation mechanisms (such as twinning for hexagonal close packed crystals) are systematically evaluated. The lattice misorientation field can be used to determine the intragranular deformation behavior in polycrystals or to describe the deformation inhomogeneity due to dislocation plasticity in single crystals. The study of indentation-induced lattice misorientation fields in single crystals sheds lights on the understanding …