LASER melting is the basis of various modern processing and fabrication techniques, such as laser surface alloying, laser welding and metal additive manufacturing. Standard methods of microstructure simulation are generally not suited to model the kinetic effects associated with rapid solidification in laser processing, especially for material systems that contain intermetallic phases. PhasePot employs a tailored phase-field model to demonstrate unique features of microstructure evolution in rapid solidification of such systems. This example demonstrates the application of the software in studying the effect of processing conditions on various microstructural features, such as the distribution of intermetallic phases in the melt pool and the heat-affected zone during laser processing of a nickel-rich Ni-Al alloy.

Scanning laser melting simulations were carried out on a polycrystalline Ni-Al alloy with 0.2 Al mole fraction. To create the initial microstructure for these simulations, isothermal solidification of the alloy was simulated in the first step. The simulated microstructure from the isothermal solidification step was subsequently used as the initial condition for the simulation of laser melting. To emulate the thermal cycle of the moving heat source in the continuous melting case, a heat-flux was applied to 20 cells at the top boundary, while the calculation domain was shifted to the right with a constant velocity. To illustrate the effect of process parameters on microstructure evolution, simulations were carried out with three different laser powers (15, 21 and 27 GW/m2) corresponding to three scanning speeds (0.5, 0.7 and 0.9 m/s). In this way, the ratio of laser power densities over scanning speeds remained constant, so that the overall heat input per unit volume of material was the same in all simulations (30 GJ/m3).

The simulations demonstrated possible microstructural features that can arise during laser processing of polycrystalline Ni-rich alloys in the Ni-Al system, including dissolution of precipitates and the segregation pattern, in addition to a strongly textured grain structure.