Quantification and localization of the liquid zone of partially remelted M2 tool steel using X-ray microtomography and scanning electron microscopy

Abstract

is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. In situ tensile tests were performed at room temperature on a ferrite-cementite steel specifically designed for this study. The evolution of the average stress in ferrite during loading was analyzed by Xray diffraction. Lattice strain measurements were performed with synchrotron ring diffraction in both ferrite and cementite. These in situ tests were complemented by macroscopic tensile and reversible tensile-compression tests to study the Bauschinger effect. In order to reproduce stresses in ferrite and cementite particles, a recently developed micromechanical Internal Length Mean Field (ILMF) model based on a generalized self-consistent scheme is applied. In this designed ferrite-cementite steel, the third ''phase'' of the model represents finite intermediate ''layers'' in ferrite due to large geometrically necessary dislocation (GND) densities around cementite particles. The assumed constant thickness of the layers is calibrated thanks to the obtained experimental data. The ILMF model is validated by realistic estimates of the Bauschinger stress and the large difference between mean stresses in ferrite and in cementite phases. This difference cannot be reproduced by classic two-phase homogenization schemes without intermediate GND layers.

Microstructure observation and quantification of the liquid fraction of M2 steel grade in the semi-solid state, combining confocal laser scanning microscopy and X-ray microtomography

“…As compared to CLSM and SEM, X-ray microtomography provides 3-D information on microstructure, as stated in Ref. [9]. In addition, a larger field of view can improve the precision of the quantification of liquid fraction and reduce the uncertainty.…”

“…This technique has been successfully used to investigate the overall and local microstructural changes occurring during partial remelting of aluminum alloys directly at high temperature [8], because the solid and liquid phases present good absorption contrast thanks to the large difference in chemical compositions. Such in situ observations have never been performed on steel grades in the semi-solid state; only ex situ investigations on M2 steel grade have been carried out on quenched specimens from the semi-solid state [9].…”

Microstructural evolution during partial melting and semisolid forming behaviors of two hot-rolled Cr–V–Mo tool steels

“…Mechanical properties and microstructural characteristics of semisolid treated X210CrW12 and 100Cr6 tool steels were investigated by Uhlenhaut et al (2006) and Püttgen et al (2007a), respectively. An X-ray microtomography were used by Gu et al (2012) to investigate the quantification and localization of the liquid phase in a partialy melted M2 tool steel. Subsequently, thixoforming of M2 tool steel lower liquid fraction was performed by the researchers mentioned above (Gu et al, 2015).…”

Application of X-Ray Microtomography to Quantify the Liquid Fraction of M2 Steel for Semi-Solid Forming Process

“…However, the 2D image analysis may lead to high uncertainties and even errors in the evaluation of the liquid fraction and in the characterization of the microstructure of the material (grain size, shape factor, etc) due to 2D sections chosen at random, possible heterogeneity and texture in the material... The real microstructure information (contiguity, grain shapes, entrapped liquid, etc) can be obtained by 3D investigations using serial sectioning techniques [7,8] as well as the non-destructive X-ray microtomography [9]. However, these experiments were mainly carried out on aluminum alloys.…”