Numerical Simulation of the Thermal Behaviour of a Ti-Ni Shape Memory Alloy During Selective Laser Melting
B-B. He, D-D. Gu, L-F. Wang and L-J. Guo
A three-dimensional (3-D) finite element method (FEM) model was developed to simulate the thermal behaviour during selective laser melting of Ti-Ni two-component powder in the ration 60:40. The moving heat source with a Gaussian distribution was considered in the simulation. The development of temperature distributions, molten pool configurations and cooling rates were comprehensively investigated. The numerical results showed the maximum temperature of the molten pool was increased from 1858 to 2429ºC and the resultant molten pool dimensions were enlarged (width: from 44 to 215 μm; depth: from 34 to 98 μm ) as the laser power increased from 150 to 300 W at a constant scan velocity of 100 mm/s. In contrast, the maximum temperature of the molten pool was decreased from 2345 to 1702ºC and the corresponding molten pool sizes were lowered (width: from 152 to 39 μm; depth: from 88 to 11 μm) when the scan velocity increased from 50 to 200 mm/s at a fixed laser power of 200 W. The average temperature of the powder bed increased as the selective laser melting (SLM) process proceeded. The cooling rates were negative before the laser beam reached the centre of the top surface of powder bed, whereas the cooling rates were positive as the laser beam moved away. The maximum cooling rate was found to occur near the centre of the top surface of the powder bed.
Keywords: Ti-Ni alloy, shape memory alloy, selective laser melting (SLM), numerical simulation, additive manufacturing (AM), finite element method (FEM), temperature distribution, cooling rate