Mesoscopic Strain Fields Measurement During the Allotropic α − γ Transformation in High Purity Iron

Abstract

The allotropic phase change from ferrite to austenite represents a moment of massive interplay between the microstructural and mechanical states of iron. The difference of compacity between the two phases induces a microplastic accommodation in the material at grain scale. However, mechanical heterogeneities resulting from the transformation process remain challenging to characterise due to the high temperature conditions it is associated with. We developed experimental equipment for in situ observation of α − γ and γ − α transformations. Images of the surface of an iron sample taken by an optical camera were used as input for a Digital Image Correlation (DIC) routine. Special care was taken to maximize image resolution to capture subgrain phenomena. Observations show that, at the mesoscopic scale, shear strain fields exhibit strong localisations that are evidence of transformations that are occurring.

Probing the Effect of Cuttings Particle Size on the Friction and Wear Mechanism at the Casing Friction Interface: A Molecular Dynamics Study

“…However, this is limited for the overall lattice structure evolution of the Fe block. On the other hand, the microstructure of the Fe block is influenced by the temperature . However, the lattice distortion of Fe atoms requires a temperature of at least 1202.2 K, and the system temperature is much lower than this .…”

“…On the other hand, the microstructure of the Fe block is influenced by the temperature. 55 However, the lattice distortion of Fe atoms requires a temperature of at least 1202.2 K, and the system temperature is much lower than this. 56 Therefore, the silica particles and the external temperature cannot dominate the change of the local atomic crystal structure of the surface material of the casing.…”

Experimental Investigation of Allotropic Transformation of Cobalt: Influence of Temperature Cycle, Mechanical Loading and Starting Microstructure

“…Dilatometric tests have been performed using a homemade device on dog bone shaped tensile specimens [16,17]. The samples were machined by electroerosion along the rolling direction.…”

Real time imaging of strain fields induced by the ferrite-to-austenite transformation in high purity iron

“…This quantity has a deviatoric nature and is not altered by dilatation, which eliminates the effects of both thermal and phase change isotropic transformations. As such, it is a good way to characterize the elasto plastic activity taking place around the ferrite-to-austenite transformation, as exemplified in [7]. Line plots of the Maximum Shear Strain are presented in Figure 2.…”

“…Yet, the scanning phase involved by the imaging process hinders real time observations, although efforts made in this direction by Ziljstra et al [6] deserve to be noted. Halfway between the two, a recent experimental set-up [7] makes use of a high resolution camera to monitor phase changes at the mesoscale. Raw images are processed using the Digital Image Correlation (DIC) technique, which has emerged as the indisputable tool to investigate strain localizations in metallic materials [8].…”