Microstructure and Property Modifications of Cold Rolled IF Steel by Local Laser Annealing

Abstract

Laser annealing experiments are performed on cold rolled IF steel whereby highly localized microstructure and property modification are achieved. The microstructure is seen to develop by strongly heterogeneous recrystallization to provide steep gradients, across the submillimeter scale, of grain size and crystallographic texture. Hardness mapping by microindentation is used to reveal the corresponding gradients in macroscopic properties. A 2D level set model of the microstructure development is established as a tool to further optimize the method and to investigate, for example, the development of grain size variations due to the strong and transient thermal gradient. Particular focus is given to the evolution of the beneficial γ-fiber texture during laser annealing. The simulations indicate that the influence of selective growth based on anisotropic grain boundary properties only has a minor effect on texture evolution compared to heterogeneous stored energy, temperature variations, and nucleation conditions. It is also shown that although the α-fiber has an initial frequency advantage, the higher probability of γnucleation, in combination with a higher stored energy driving force in this fiber, promotes a stronger presence of the γ-fiber as also observed in experiments.

Modeling of grain growth under fully anisotropic grain boundary energy

“…A large number of studies on mesoscale simulations of grain structure evolution in polycrystals, using different modeling approaches, have been published over the years. The numerical methods used comprise, for example, Monte Carlo Potts formulations [12][13][14], phase fields [15][16][17][18][19][20], level sets [21][22][23], cellular automata [24,25] and vertex models [26,27]. These different approaches to modeling of microstructure evolution in polycrystals are reviewed in [28].…”

Analysis of the Advantages of Laser Processing of Aerospace Materials Using Diffractive Optics

“…Applied in this manner, laser heating permits us to increase the plasticity of local sections of the material. The use of laser annealing can be extraordinarily effective for processing materials such as hard alloys, heat-resistant steels and alloys, and hardened or work-hardened alloys [69,70].…”

Recrystallization Study of the Al4.5wt%Cu Alloy Conventionally and Unidirectionally Solidified, Deformed and Heat Treated

“…Authors such as 41,44,45 explain that the greater is the deformation of the material, greater will be the nucleation of new grains. The cold working of metallic materials increases the stored energy on its microstructure, most significantly through an increased dislocation density in the crystal structures.…”