Theses and Dissertations

Issuing Body

Mississippi State University

Advisor

El Kadiri, Haitham

Committee Member

Oppedal, Andrew L.

Committee Member

Barrett, Christopher

Date of Degree

8-10-2018

Document Type

Graduate Thesis - Open Access

Major

Mechanical Engineering

Degree Name

Master of Science

College

James Worth Bagley College of Engineering

Department

Department of Mechanical Engineering

Abstract

Hexagonal close packed (hcp) crystal structures, such as magnesium and titanium, provide formidable strength in relation to density. Current interests in reducing CO2 emissions, hold magnesium as a contender to lightweight passenger vehicles. Although significant decreases in mass could be achieved through magnesium, poor formability and energy absorption capacity limit the possibility for cost-effective production. This Master’s thesis aims to observe the microstructure and micro texture evolution induced by twinning using interrupted electron backscattered diffraction (EBSD) characterization in order to determine potential mechanisms causing early failure of magnesium alloys. This study revealed {10-11} contraction twins at stress levels contrary to the basic hypothesis of the Schmid effect revealing the importance of non-Schmid effects in damage. Furthermore, it was observed that crack nucleation occurs in magnesium alloys, due mainly to interaction between twins and microstructure defects and form inside contraction twins, causing cleavage-like terraces in the fracture surface.

URI

https://hdl.handle.net/11668/20970

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