Analysis and fast modelling of microstructures in duplex stainless steel formed by directed energy deposition additive manufacturing

Parametric Study of Directed Energy Deposition Of Duplex Stainless Steels To Optimize Ferrite-Austenite Phase Ratio And Residual Stresses

“…In [17] several printing strategies using a DED machine have been proposed to produce thinwalled structures (50 mm long by 16 mm high) made of 100 layers. In this contribution, two of them are studied in more details: 1) the reference strategy in which the laser power is set to 250 W and the laser velocity is 2000 mm.min −1 (see [17] for details), and 2) an optimized strategy, identical to the reference excepted that the substrate temperature is controlled during fabrication to obtain more balanced and uniform ferrite-austenite phase fraction. All process parameters, and thermal and diffusional properties of SAF 2507 DSS are listed in [17].…”

“…In this contribution, two of them are studied in more details: 1) the reference strategy in which the laser power is set to 250 W and the laser velocity is 2000 mm.min −1 (see [17] for details), and 2) an optimized strategy, identical to the reference excepted that the substrate temperature is controlled during fabrication to obtain more balanced and uniform ferrite-austenite phase fraction. All process parameters, and thermal and diffusional properties of SAF 2507 DSS are listed in [17]. On this basis, thermo-mechanical computations are carried out in this contribution to estimate the mechanical effect of the optimized strategy with respect to the reference strategy.…”

“…This simulation of the temperature field history has already been validated experimentally by infrared measurements using pyrometers [11] and an infrared camera [13], and was used to predict grain growth [14,15,16] during thermal cycling. (ii) In addition, we use a fast model of diffusion of alloying elements based on analytical solutions to take into account phase transitions in DSS [17], which has recently been developed and coupled to [11] to predict ferrite-austenite phase ratio in thin-walled structures, with satisfying comparison against experimental measurements performed by electron backscatter diffraction techniques (EBSD). (iii) Furthermore, stresses also strongly depend on the complex temperature history, which should also be taken into account in the optimization of the phase field.…”

“…General principles of the numerical models are briefly recalled here for the sake of clarity. The reader is refereed to [11,17,13] for details.…”

Very fast simulation of growth competition between columnar dendritic grains during melt pool solidification

“…In the literature, several approaches have been used to assess grain size in melt pool solidification [27]. In this paper a simpler empirical approach [28,29] is chosen to directly relate the grain size d (µm) and the cooling rate at the solidification front in the form of a power law:…”