Materials Technology

Key research areas

Materials optimisation, creep resistant materials, aluminium alloys

The main objective is to improve and develop methods for accurate predictions of features in the microstructure as well as material property values. Composition–microstructure-property relations (CMPR) are established with sufficient precision that they could be used in engineering design. This enables a fully mathematical optimisation of materials for given applications.

To achieve this goal the accuracy in models for describing the microstructure development has been improved. This applies for example to the nucleation, growth and coarsening of particles with the help of thermodynamic modelling. For creep resistant materials models for solid solution, particle, dislocation and substructure hardening have been established. These models are so accurate that quantitative predictions of creep properties have been possible to make for the first time without using fitting parameters. By analysing microstructure mechanisms, CMPR for mechanical properties are set up for non-hardenable and hardenable aluminium alloys. Properties covered include yield strength, tensile strength, fatigue strength and hardness as well as technological properties such as general corrosion resistance, machinability and weldability.

Toughness of duplex stainless steels

Fracture toughness testing is performed both for different duplex stainless steels. The results are evaluated by the master curve analysis and deriving a reference temperature. The reference temperature corresponds to the onset of cleavage cracking. The reference temperature is typically quite low implying that the steels can be used down to low temperatures without the risk for brittle failure. Principles for design against brittle failure are developed. Some of these principles are implemented in the European Pressure Vessel Code. Microstructure mechanisms are also analysed. Sigma phase precipitation is known to embrittle duplex stainless steel. Accordingly, heat treatment and welding must be performed carefully. Nucleation and diffusional growth of sigma and other phases in the duplex stainless are analysed in order to ensure a high toughness shown both base and weld material.

Copper for nuclear waste management

Copper is going be used in canisters for storage of nuclear waste. The canisters are going to exposed to external pressure at somewhat elevated temperatures for extended periods of time, which gives rise to creep. Fundamental models for creep deformation are formulated without the use of fitting parameters. These models are sufficiently accurate that they can and are used in FEM computations of the canisters. The crucial role of the welds has initiated studies of the processing as well as properties of the friction stir welds.

Fatigue properties of welded aluminium profiles

The fatigue behaviour of friction stir welded aluminium alloys is investigated. The complex geometry of the profiles as well as of the welds is taken into account.

Industrial use of the results

Practically all of the running and past projects are or have been performed in collaboration with national and international industry. In this way it is ensured that the problems studied are of direct technical relevance.