The Field-of-Expertise Advanced Materials Science is an interdisciplinary network of researchers at the TU Graz in chemistry, physics, architecture, mechanical engineering, civil engineering, electrical engineering and geodesy who discover, characterize and model materials, functional coatings and components.
Due to the current COVID-19 situation, Advanced Materials Day 2020 will be held in a hybrid form: the posters will be physically displayed but the discussion will be done virtually.
Metals and Alloys
Moderator: Christof Sommitsch
Evaluation of Quenching and Partitioning C20MnSi Steel microstructure
Abstract: Quenching and partitioning is a novel heat treatment that has been proposed to give a good mixture of tensile strength and the total elongation by producing martensitic steel containing a certain amount of retained austenite (RA). The 2-step Q&P process enhances the stabilization of austenite by carbon enrichment through the segregation of the carbon from martensite to RA. The microstructure was investigated using LOM, SEM, EBSD, and XRD. The X-ray diffraction has been carried out in order to assess the retained austenite (RA%) volume fraction. It showed convergent RA fractions for different heat treatments with different quenching and partitioning temperatures. However, for different holding time in quenching and partitioning steps, recognizable differences in RA% can be observed. The mechanical properties obtained by Q&P reported for 20CMnSi steel at different Q&P temperatures showed comparable results. While, at different Q&P holding time, observable change in the mechanical properties is reported.
Hydrogen embrittlement of advanced high-strength steels
Andreas Drexler, Institute of Materials Science, Joining and Forming, Research Group Tools & Forming
Abstract: Advanced high-strength steels have emerged interest in the automotive industry, because of the potential to reduce weight and to increase fuel efficiency. However, with increasing strength steels become prone to hydrogen embrittlement/stress corrosion cracking. Hydrogen absorbed during production or service can easily penetrate the components and lead to time-delayed brittle failure. The delay in time is crucial, because structural components have to be crack free for the whole lifetime of a car. Successful assessment strategies for advanced high-strength steels are still rare and experimental testing is very time consuming and expensive. Furthermore, hydrogen embrittlement tests are performed under controlled laboratory conditions for limited time and extrapolation to the lifetime of a car needs special consideration.
In our research we are focusing on both experimental hydrogen embrittlement testing and simulations. For that purpose, electrochemical and corrosive hydrogen charging cells were established in the corrosion labs. The subsequent tests are performed under different strain rates and temperatures to investigate the rate effect on the local hydrogen accumulation in the samples. Our simulations are based on thermodynamic models describing the hydrogen uptake, diffusion and trapping at microstructural defects and can be coupled with mechanical finite element analyses or CALPHAD based routines, such as MatCalc. The latter allows us virtual testing of new alloy compositions or processing routes to develop more resistant microstructures to hydrogen embrittlement.