A Comprehensive Material Model for the Super-Duplex Stainless Steel SAF2507 in a Welding Environment

The aim of this work is to describe a reliable methodology for determining parameters of a material model suitable for implementation in a welding simulation using the finite element method (FEM). The adopted methodology employs a multi-scale approach integrating a microstructure evolution model, a representative volume element (RVE) calibrated through experimental methods, including a thermal–mechanical simulator, and electron backscatter diffraction (EBSD) experiments. The result is a complete material model, which covers thermal, mechanical and metallurgical material models for SAF2507 (EN 1.4410), that shows promising results and was successfully implemented in finite element (FE) code. A direct comparison of experimental and calculated results shows a deviation of up to 12% for the phase fraction of austenite and 25% for the mean grain diameter of ferrite

In situ analysis of the effect of high heating rates and initial microstructure on the formation and homogeneity of austenite

Decreasing processing time of a quench and temper heat treatment is of high interest for industry due to the possibility of cost reduction. One option to reduce processing time is to shorten the austenitizing cycle by applying high heating rates and minimum holding times. However, due to the high heating rates, the analysis of their influences on the formation kinetics of austenite and its crystallographic parameters is challenging. Thus, this work concentrates on the in situ analysis of the austenitization process by means of high-energy X-ray diffraction to study a range of heating rates applied to ferritic–pearlitic and soft annealed initial microstructures. The transformation kinetics from ferrite/pearlite and soft annealed state to austenite, the cementite dissolution behavior and the homogeneity of the freshly formed austenite were analyzed. The results indicate three distinct steps of austenite formation independent of initial microstructure and heating rate: (1) nucleation of carbon-rich austenite at cementite–ferrite interfaces, (2) growth of austenite phase fraction accompanied by a reduction of the carbon content, until reaching the mean carbon content of the steel, followed by growth of the austenite grain size, (3) regarding austenite homogeneity, the combination of austenitization temperature and initial microstructure are the main influencing factors

Experimental and Numerical Investigation of the Deformation and Fracture Mode of Microcantilever Beams Made of Cr(Re)/Al2O3 Metal–Matrix Composite

This work presents a combined experimental and computational study of the deformation and fracture of microcantilever specimens made of chromium(rhenium)-alumina metal–matrix composite (MMC), with a particular focus on the failure properties of the metal–ceramic interfaces. The obtained experimental results show that the bending strength of microcantilevers containing alumina particles in critical cross-sections near specimen’s fixed end is considerably higher than that of unreinforced chromium(rhenium) samples. Brittle cracking along chromium–alumina interfaces is the dominant fracture mode of the composite microcantilevers. The interface characteristics are determined in an indirect way by numerical simulations of the experiment with account of the actual specimen microstructure from the scanning electron microscope (SEM) images. A parametric study demonstrates that the overall material response may be reproduced by different sets of model parameters, whereas the actual failure mode permits to discriminate among the possible alternatives. Using this approach, the in situ values of the chromium–alumina interface cohesive strength and the fracture energy are estimated

Typical residualized RT time series is shown for one patient (P029) and one condition (0-back non-jittered) for illustrative purposes.

<p>Successive RTs are connected with black lines; the outer horizontal dashed lines mark the threshold for particularly low and high RTs (Gaussian 1% threshold, cf. Methods). Very fast or slow reactions, exceeding the thresholds, are marked with circles. The red line shows the 40 s running median of values within the thresholds (background response fluctuation) and the inner horizontal dashed lines its tercile boundaries (1/3 of all values lying in each partition). The occurrence of each of these events (low/high value or omission) was associated with the tercile of the background response fluctuation. It can be seen that the few very fast RTs occur during a time of fast background RTs; similarly the larger number of very slow RTs (contributing to τ) occur preferentially during phases of slow background RT fluctuation.</p