Laser materials transformations - An overview

Abstract

Directed energy heat sources are important tools of the materials scientist for heat treating materials to change their surface properties. There has been great interest in employing carbon dioxide and. Nd-YAG lasers as directed energy heat sources. These lasers provide directed beams of radiant energy far more intense than flames, arcs or plasma arcs. They have advantages with respect to electron beams: namely, shallower absorption depth; better focus and more controllable spatial distribution of intensity; no x-ray hazard; and, atmosphere capability. Because of these features, these lasers have been used to induce materials transformations such as: martensite transformation in ferrous alloys; melting for purposes of alloying, cladding, incorporation of hard dispersoids or formation of metastable phases; and recovery or recrystallization of strain hardened materials.An important consideration in the application of lasers to produce useful materials transformations is the predictability of the thermal treatment. We will compare thermal cycles measured at the surface of irradiated samples to those predicted by linear heat flow theories. The intensity of laser heat sources makes possible very rapid heating and cooling of materials with minimum heat effect outside of the transformed zone. Results obtained in the author’s laboratory by applying this principle to the hardening of a steel to improve its fatigue resistance and to the formation of metastable phases in Ag-Cu alloys will be presented.Directed energy heat sources are important tools of the materials scientist for heat treating materials to change their surface properties. There has been great interest in employing carbon dioxide and. Nd-YAG lasers as directed energy heat sources. These lasers provide directed beams of radiant energy far more intense than flames, arcs or plasma arcs. They have advantages with respect to electron beams: namely, shallower absorption depth; better focus and more controllable spatial distribution of intensity; no x-ray hazard; and, atmosphere capability. Because of these features, these lasers have been used to induce materials transformations such as: martensite transformation in ferrous alloys; melting for purposes of alloying, cladding, incorporation of hard dispersoids or formation of metastable phases; and recovery or recrystallization of strain hardened materials.An important consideration in the application of lasers to produce useful materials transformations is the predictability of the thermal tre...