Investigation of the coarse grained heat-affected zone microstructure and hardness of multipass welded X65 linepipe steel.

In this thesis the effect of single and multipass welding on the microstructure and hardness of X65 linepipe steel of four different chemical compositions was investigated. The welding was simulated for three different heat inputs and two second pass peak temperatures. The thermal simulation has been achieved by simulating the CGHAZ with a...

Orientation dependence of the martensite transformation in a quenched and partitioned steel subjected to uniaxial tension

The orientation dependence of the austenite-to-martensite transformation during uniaxial tensile testing was modelled using the phenomenological theory of martensite crystallography and the mechanical driving force. It was validated experimentally by means of electron backscatter diffraction measurements on a pre-defined zone of a quenched and...

Unravelling the structural and chemical features influencing deformation-induced martensitic transformations in steels

A combination of Electron Back-Scattered Diffraction (EBSD) and high-sensitivity Electron Probe Micro-Analysis (EPMA) was used to correlate the changes in microstructural features upon deformation with local chemical composition in Transformation-Induced Plasticity steels. A novel cleaning procedure was developed that allows complete monitoring...

Micromechanisms of Failure under Static Loading in Sheet Metals for Automotive Applications

Deformation-induced austenite grain rotation and transformation in TRIP-assisted steel

Uniaxial straining experiments were performed on a rolled and annealed Si-alloyed TRIP (transformation-induced plasticity) steel sheet in order to assess the role of its microstructure on the mechanical stability of austenite grains with respect to martensitic transformation. The transformation behavior of individual metastable austenite grains...

Nucleation of ferrite in austenite: The role of crystallography

The nucleation mechanisms during solid-state phase transformations in polycrystalline materials are still not completely understood. The nucleation stage has a strong influence on the overall evolution of phase transformations, which determines the final microstructure and thereby the properties of the material. The understanding of grain...

Fundamentals of Rolling Contact Fatigue

In the mechanical industry there is a need for continuous development towards increasing performance of various types of machinery. Critical components in such machines are exposed to gradually harsher operating environments involving higher cyclic stresses and operating temperatures. Examples of such fatigue-exposed components are gears,...

Equal-Channel angular pressing of high-carbon steel

This master thesis deals with the research to the effects of severe plastic deformation on the development of the microstructure and the mechanical properties of three low-alloyed high-carbon steels. The steels investigated include a hypo-eutectoid, an eutectoid and a hyper-eutectoid steel containing 0.61, 0.81 and 1.22 weight-percent carbon....