Microstructure Selection in Laser Remelted Fe–C–Si Alloys

• Published in: International journal of materials research Vol. 89; no. 11; pp. 751 - 757
• Main Authors: Lima, Milton S. F., Gilgien, P., Kurz, Wilfried
• Format: Journal Article
• Language: English
• Published: De Gruyter 29.12.2021
• ISSN: 1862-5282; 2195-8556
• DOI: 10.3139/ijmr-1998-0144

Laser surface remelting at various velocities has been employed to study the selection of microstructures of high-purity Fe–C–Si alloys containing nominally 3.2 to 4.2 wt.% C and 1 to 3 wt.% Si. The microstructure of the remelted region consisted of metastable Fe–Fe C eutectic (ledeburite) or austenite dendrites, with interdendritic eutectic. Furthermore, ledeburite presents two solid-liquid interface morphologies: planar and cellular. The competition between the austenite dendrites and the ledeburite eutectic as a function of solidification rate has been experimentally determined. The critical velocity which destabilizes the planar Fe–Fe C eutectic with respect to primary austenite dendrites, was of the order of several mm/s and depends on the initial composition of the alloy. The critical velocity for the destabilization of the eutectic interface leading to two-phase cells was 0.44 mm/s, for the alloy containing 4.2 wt.% C and 1 wt.% Si. Theoretical calculations of the coupled zone have been performed using current microstructure selection models. The results of the simulation were then used to construct a microstructure map which was compared with experimental results.