Characterization of internal interfaces in polycrystalline materials

Graduate work for approximately 4 years

Degree awarded after completing all requirements: PhD in Material Science and Engineering (Sw. Tekn. Doktor i Konstruktionsmaterial)

Advisor: Prof. Magnus Odén ( magnus.oden@ltu.se )

Location: Engineering Materials, Luleå University of Technology ( www.sirius.ltu.se/material/ )

General information about graduate studies at Luleå University of Technology can be found on www.ltu.se/eng/index.php

This project focuses on describing and incorporating internal interface properties in polycrystalline material models. An interface here primarily means a grain boundary but also coherent interfaces between different phases.

In nanostructured materials internal interfaces are of great importance since the volume fraction material located in the vicinity of an interface is substantial due to for example extremely small grains. The interfaces are then the dominating structure and their properties will decide the overall behavior of the material. Critical to understanding an interface is to determine elements present and their positions, bond structure, strains, and dislocation structure and to understand how these change when a global parameter such as temperature or mechanical stress is applied. It is also essential to understand how the interface interacts with the interior of a grain, for example during dislocation motion or atom diffusion.

This PhD-project contains two approaches: (1) fabricate model material based on powder metallurgy processes to study internal interfaces; (2) develop a mathematical description of the interface.

The synthesis and characterization part of the project involves use of advanced analytical tools such as scanning probe microscopy, electron microscopy, spectroscopic methods, x-ray diffraction and thermal analysis. The graduate student will be trained to use these equipments independently. A technically relevant metallic model system will be chosen such as a low alloyed stainless steel grade which will be subjected to variations in alloying content, temperature and mechanical load. For each combination both external and internal interfaces will be characterized.

The theoretical approach involves a review of existing models and implementation of promising candidates. In a second step the models should be adopted to capture the phenomena observed during the experimental part.