PSI - Issue 69

Mohammadjavad Abdollahzadeh et al. / Procedia Structural Integrity 69 (2025) 2–19

9

C * = 1 " ) " 9 %," 61 ' ) ' 9 %,' 1 " ) " 61 ' ) '

(18)

Fig.4: Schematic diagram of cells and phases. In this figure, “L” means Liquid, “S” means Solid, and “L/S” means a mix of liquid and solid (mushy zone)

The comprehensive illumination of both the velocity and pressure fields is facilitated by the continuity and momentum equations. To determine the temperature field, it is advantageous to employ the energy equation premised on the enthalpy method. When combined with the momentum equation, this method allows for the precise calculation of the temperature field relevant to the LPBF process [41]. ρ6 ! ! : & + &8V8⃗ ⋅ ∇(h7 = −∇ ⋅ (K∇T) + q̇ (19) In the Eq (19), k is the thermal conductivity, T is the temperature, h is the enthalpy, and q is the external heat source. Enthalpy is linked to the other parameters and can be defined as follow [41, 56, 57]. h=C * ⋅T+α ⋅ L 1 (20) α(T)=J 0, if T⩽T ; <4< ( < ( 4< ) , if T ; > < ? (T−T /01 )+σ @ (22) The physical attributes and morphology of the fabricated components are influenced by the recoil pressure exerted on the melt pool throughout the LPBF process. This pressure comes into play when the pool's temperature rises to, or surpasses, the evaporation point of NiTi. The recoil pressure can be computed via Equation (23) [33, 40, 41, 57]. Pr≅0.54P @ exp 6L A <4< (* B<< (* 7 (23) In the aforementioned equation, P 0 denotes the atmospheric pressure, while L ν signifies the latent heat of vaporization. The terminologies 'surface temperature', 'liquid-vapor equilibrium temperature', and 'universal gas