![]() Our focus is on the advances made in the understanding of the mechanisms for nucleation and grain refinement. In this paper, we present an overview of the current studies of interfacial segregation behavior, the structure and chemistry of interfaces, and their impacts on the subsequent heterogeneous nucleation and grain initiation processes. Such interfacial segregations significantly affect nucleation potency of the substrates, resulting in either promoting or impeding the heterogeneous nucleation process during solidification. For instance, Al 3 Ti 2DC and Ti 2 Zr 2DC at the Al/TiB 2 interface, Y 2 O 3 2DC at the Mg/MgO interface, and a Si-rich 2DS layer at Al-Si/TiB 2 interface have been identified. Extensive examinations on metal/substrate (M/S) interfaces at atomic scale by the state-of-the-art aberration (Cs) corrected STEM and associated EDS and EELS have shown that alloying elements in liquid melts tend to segregate at the interfaces, leading to the formation of various 2-dimensional compounds (2DCs) or 2-dimensional solutions (2DSs), depending upon segregation behavior of the elements. The potency of the substrates for nucleation is mainly dependent upon the atomic arrangements on the substrate surface, which are affected by the lattice misfit between the substrate and the nucleated solid, the surface roughness at atomic scale, and the chemical interaction between the substrates and the melt. Correlative electron backscattered diffraction and transmission electron microscope analysis implies that the significant activation of non-basal 〈a〉 slip may suppress Lüders deformation.ĭuring solidification of metallic materials, heterogeneous nucleation occurs on substrates, either endogenous or exogenous. Stretching the sheet along the transverse direction causes as twice as much Lüders strain as stretching it along the rolling direction. ![]() Correlative transmission electron microscopy and atom probe tomography analysis revealed the segregation of Ca-Zn co-clusters to dislocations after 3% strain, indicating that dislocation locking by the Ca-Zn co-clusters caused the yield-drop. Digital image correlation strain mapping shows that the Lüders deformation after a yield-drop is a distinct phenomenon that only occurs in the Zn-containing sample. ![]() This study reports the effect of Zn addition on discontinuous yielding in Mg-1.2Al-0.5Ca based low-alloyed magnesium alloy sheets. Clarifying the origin of the yielding phenomenon is essential for preventing the deterioration of the flow stability and surface finish of magnesium alloy sheet products.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |