In-situ analysis of phase transformations in a supermartensitic stainless steel: A magnetic approach

This thesis studies in-situ the phase transformations during heat treatment of two advanced steels: a supermartensitic stainless steels (SMSS), on which the main focus of this work is, and Fe-C-Mn-Si steels. A magnetic technique, based on the analysis of saturation magnetization, is utilized as the primary analysing tool. The scientific aim of...

Developing novel heat treatments for automotive spring steels: Phase transformations, microstructure and performance

This Ph.D. thesis investigates the substitution of quenching and tempering treat-<br/>ments by isothermal bainitic treatments in automotive spring production. An isothermal bainitic treatment has benefits mainly in terms of energy savings, but it can also prevent quench cracking, distortion and residual stresses, commonly found in quenched and...

Molecular dynamics simulations of martensitic transformation in iron

The aim of this PhD. thesis is to use molecular dynamics (MD) simulations to comprehend the mechanisms governing nucleation and growth of martensite phase in austenitic phases in iron. In view of this objective, the thesis is divided into five parts: Chapter 2 reviews previous investigations of the fcc-to-bcc transformation in iron by MD...

Artefact biography 2.0: the information value of corroded archaeological bronzes

The different phases in the life of archaeological objects can be described by artefact biography. This dissertation defines an updated version: artefact biography 2.0, and the life phases of Early Iron Age bronze studs from Oss-Zevenbergen, the Netherlands, are elaborated. Throughout the thesis, the research revolves around information value....

Yield and flow stress of steel in the austenitic state

Steels for nuclear reactors: Eurofer 97

These days, climate change and its consequences regularly make the news. Sea levels are rising, poles are defrosting, species are becoming extinct, the ozone layer is being destroyed and the earth's temperature is increasing. These symptoms convey a clear call to action: the preservation of the environment needs to be of the highest concern. In...

Optimising mechanical behaviour of new advanced steels based on fine non-equilibrium microstructures

This Ph.D. thesis investigates the relation between microstructural and mechanical properties of Advanced High Strength Steels (AHSS), with the goal of developing a microstructure with optimised mechanical properties. Among different grades of AHSS, Quenching and Partitioning (Q&P) steel which is composed of thin films of retained austenite...

Tempering of martensitic steel for fasteners: Effects of micro-alloying on microstructure and mechanical property evolution

The research presented in this thesis aims to deepen our understanding of the effect of micro-alloying on the microstructure and mechanical property evolution during tempering of martensitic steel for fasteners. The ongoing trend of engine down-sizing has led to the need for stronger and more temperature resistant fasteners than currently...

Mathematical Modelling of Nucleating and Growing Precipitates: Distributions and Interfaces

Steels with higher strength and better formability are increasingly required by the automotive industry because they can provide higher safety, reduce energy consumption and thus lead to a better environmental protection. To meet these requirements, it is a sustainable effort for steel industry to develop high strength formable steels. One of...

Microstructural evolution in deformed austenitic TWinning Induced Plasticity steels

This thesis studies the effect of plastic deformation on the stability of the austenitic microstructure against martensitic transformation and diffusional decomposition and its role in the phenomenon of delayed fracture in austenitic manganese (Mn)-based TWinning Induced Plasticity (TWIP) steels. The transformation to alpha’-martensite upon...

Stereological Estimation of Anisotropic Microstructural Features: Applying an Oriented Cylinder Model to Dual Phase Steel

Microstructural banding is explored in 2D and 3D using serial sectioned micrographs. The banding is quantified using two parameters called the Band Continuity Index Cb and the Perpendicular Continuity Index Cp. The indexes determined from the 2D micrographs is shown to be sufficient for estimating the distribution of the bands in 3D. A...

Microstructure Control of Fire-resistant, Low-alloy Steel; An in-situ 3D X-ray Diffraction and A Small-angle X-ray Scattering Study

The research presented in this thesis aims at deepening our understanding of the formation of the microstructure of steel during thermal processing in order to control the microstructure and thereby improve the fire-resistance of low-alloy steel. The strength of steel decreases during a fire mainly due to the following changes in the...

Thermostatistical theory of plastic deformation in metals

This work aims to describe plastic deformation and microstructure evolution of metals at various scales in terms of dislocation behaviour. The theory is based on statistical thermodynamics, where the entropy is proposed to incorporate the possible paths for dislocation motion. Other than estimating the velocity gradients a dislocation may reach,...

Thermo-Mechanical Fatigue of Compacted Graphite Iron in Diesel Engine Components

Cast iron components in combustion engines, such as cylinder blocks and heads of trucks, are exposed for long periods of time to elevated temperatures. Moreover, the engines are started and stopped frequently during their operational life, constituting a large number of heating and cooling cycles. In geometrical complex components the sudden...

Modeling of Precipitation Sequence and Ageing Kinetics in Al-Mg-Si Alloys

Al-Mg-Si alloys are heat treatable alloys in which strength is obtained by precipitation hardening. Precipitates, formed from a supersaturated solid solution during ageing heat treatment, are GP-zones, B", B´ and B-Mg2Si. Precipitation kinetics and strength vary with alloy composition and process parameters. There is still a need for property...

Austenite formation in C-Mn steel

The production process of almost all modern steels involves austenitization formation of the austenite phase upon continuous heating. Many of the microstructural features and properties that are obtained upon subsequent cooling are to a large extend determined by the evolution of the microstructure and chemical inhomogeneities during...

Physically-based modelling of material response to welding

Abstract not available