Understanding Defect-assisted Precipitation to Control Mechanical Behaviors in Magnesium Alloys

Description

To respond to the rapid climate change and the increasing energy crisis, energy-efficient and high-strength lightweight materials are highly desirable in advanced technologies in transportation, propulsion, aerospace industries, etc. Magnesium alloys are promising metallic materials to supplant their aluminum and steel counterparts in structural applications due to their lower densities. Part of the reason for their limited applications is their relatively low strength. Precipitation of fine particles in a supersaturated matrix is a common method to strengthen materials and has achieved notable success in developing high-strength steel and aluminum alloys. In contrast, its improvement capacity for magnesium alloys appears inadequate using conventional aging treatment. Pre-existing crystal defects can alter the precipitation trajectory by modifying the nucleation and growth of particles, holding the potential for further improvement in strengthening magnesium alloys. Encouraging process engineering of defect-assisted precipitation to change mechanical performance has been reported in applied studies. However, the fundamental knowledge of how distinctive defects in magnesium manipulate the precipitation process to control mechanical behavior still needs to be discovered.  In this proposed project, the PI aims to understand the role of two distinctive defects in magnesium, dislocation and twin boundary, on the precipitation process in representative magnesium alloys. The experimental studies will systematically compare the well-known defects,dislocation and ordinary grain boundary, to benchmark the effect on precipitation process. We will employ bulk and small-scale mechanical testing to analyze the strengthening effectiveness of defect-assisted precipitation. Meanwhile, state-of-the-art microstructure characterization will be performed to elucidate the defect-solute interaction and deformation mechanism after precipitation.     The project is expected to offer key insights into controlling defect-assisted precipitation to develop magnesium alloys with superior mechanical properties. The scientific knowledge obtained in this project will also be instructive to other precipitation-hardenable metallic materials with the same crystal structure as magnesium.