Interface Structure and Deformation Mechanisms of Mg/Nb Multilayers

Authors

Xinyan Xie, University of Nebraska - LincolnFollow

First Advisor

Jian Wang

Date of this Version

Summer 7-2018

Citation

Xie, Xinyan, "Interface Structure and Deformation Mechanisms of Mg/Nb Multilayers" (2018). Mechanical (and Materials) Engineering -- Dissertations, Theses, and Student Research. MS thesis, University of nebraska-Lincoln.

Comments

A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Mechanical Engineering and Applied Mechanics, Under the Supervision of Professor Jian Wang. Lincoln, Nebraska: July, 2018

Copyright (c) 2018 Xinyan Xie

Abstract

Magnesium (Mg) and its alloys, as the lightest structural materials, are very attractive for a range of weight sensitive applications, such as aircraft engine, transportation industry and so on. However, their further applications are limited due to the weak properties, such as the low strength and poor ductility. In recent years, advanced techniques aiming at the modification of the microstructures, have been developed to promote the properties of Mg and its alloys, such as modifying the texture, refining the grain size, forming the intermetallic phase, and introducing the interfaces or stacking faults into the systems. Constructing Mg/Nb multilayers, which introduces a high density of interfaces into the system, is one of the most promising techniques to improve mechanical properties. The corresponding mechanism gives the direction for the improvement of this technique. In this study, a comprehensive literature review related to Mg/Nb multilayers is first summarized and studied. Then, the interface structures and the network of interfacial dislocations were determined by the atomically informed Frank-Bilby (AIFB) method. With Molecular Dynamics (MD) simulation, it has been found that Mg/Nb interfaces remain stable during deformation while {10-12} twinning is the dominant deformation mode in Mg layers when the Mg/Nb multilayer is subjected to compressive loading along [10-10] direction in Mg. Abnormally, {10-12} twinning is accomplished by BP transformation, which leads to considerable yield strength, high hardening rate, and significant back stress in nearby layers. All the factors explain the superior mechanical properties of Mg/Nb multilayers.

Advisor: Jian Wang