Cracking and Failure in a High Strength Low Alloy Steel during Solidification

The present study focuses on characterizing cracks and fracture that appeared during solidification in the segregated zones of the as-cast structure of a large size ingot made of high strength low alloy steel. Solidification experiment was conducted, using Gleeble® 3800 thermo-mechanical simulator, on samples taken from the ingot/hot top interface of a 40 MT (Metric Ton) ingot. The thermal cycle consisted in heating from ambient temperature to 1385 °C with a constant heating rate of 2 °C/s followed by a free cooling. Optical and scanning electronic microscopies were used to analyze and quantify the cracked regions. Microstructural observations revealed that shrinkage during rapid solidification of melted grain boundaries ultimately led to the initiation and propagation of cracks.

Effect of Heat Treatment on Dendritic Microsegregation of an Al-Cu-Si Alloy

Solidification experiment a graphite mold was carried out on ternary alloy Al-4.61Cu-0.92Si and typical dendrite microstructure was obtained. The influence of heat treatment on microsegregation between the dendrite, and the amount and morphology of the non-equilibrium eutectic phases were studied. Line scans results shows that the dendrite microsegregation disappeared after heat treatment under temperature near the ternary eutectic point. And the amount of eutectic phases is decreased obviously and the morphology of most θ-phase is changed from normal pattern to sphere or nearly spherical.