Nanoengineered Laser Shock Processing via Pulse Shaping for Nanostructuring in Metals: Multiscale simulations and experiments

Modulating the heating and cooling during plastic deformation has been critical to control the microstructure and phase change in metals. During laser shock peening under optimal elevated temperatures, high-density dislocations and nanoprecipitates can be generated to greatly enhance material strength and fatigue life in metals. In this paper, we propose a general methodology to modulate the heating and cooling during laser shock processing via temporal pulse shaping, namely dual pulse laser shock peening (DP-LSP), which combines both ultrafast-heating and laser shock peening in one operation to generate desired microstructure and mechanical property. Single pulse LSP was able to remelt large second phase precipitates due to fast cooling, resulting in smaller grains (500nm), while using DP-LSP with appropriate pulse durations, dynamic precipitation effects can generate nanosized (30nm) intermetallic phase Al3Ti with high density. By generation of grain size refinement, high density nanoscale precipitates, and dislocations, the yield strength increase by 18% and 102% compared with single pulse processing, and original sample respectively. A phase-field model (PFM) and multiscale dislocation dynamics (MDD) were applied to study dislocation dynamics and nanoprecipitation generation during DP-LSP, and their interaction. The work provides a basis for controlling microstructure by DP-LSP to enhance mechanical properties in metals.