Final published version
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Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
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TY - JOUR
T1 - Strengthening control in laser powder bed fusion of austenitic stainless steels via grain boundary engineering
AU - Sabzi, H.E.
AU - Hernandez-Nava, E.
AU - Li, X.-H.
AU - Fu, H.
AU - San-Martín, D.
AU - Rivera-Díaz-del-Castillo, P.E.J.
PY - 2021/12/15
Y1 - 2021/12/15
N2 - A new approach to modelling the microstructure evolution and yield strength in laser powder bed fusion components is introduced. Restoration mechanisms such as discontinuous dynamic recrystallization, continuous dynamic recrystallization, and dynamic recovery were found to be activated during laser powder bed fusion of austenitic stainless steels; these are modelled both via classical Zener-Hollomon and thermostatistical approaches. A mechanism is suggested for the formation of dislocation cells from solidification cells and dendrites, and their further transformation to low-angle grain boundaries to form subgrains. This occurs due to dynamic recovery during laser powder bed fusion. The yield strength is successfully modelled via a Hall–Petch-type relationship in terms of the subgrain size, instead of the actual grain size or the dislocation cell size. The validated Hall–Petch-type equation for austenitic stainless steels provides a guideline for the strengthening of laser powder bed fusion alloys with subgrain refinement, via increasing the low-angle grain boundary fraction (grain boundary engineering). To obtain higher strength, dynamic recovery should be promoted as the main mechanism to induce low-angle grain boundaries. The dependency of yield stress on process parameters and alloy composition is quantitatively described.
AB - A new approach to modelling the microstructure evolution and yield strength in laser powder bed fusion components is introduced. Restoration mechanisms such as discontinuous dynamic recrystallization, continuous dynamic recrystallization, and dynamic recovery were found to be activated during laser powder bed fusion of austenitic stainless steels; these are modelled both via classical Zener-Hollomon and thermostatistical approaches. A mechanism is suggested for the formation of dislocation cells from solidification cells and dendrites, and their further transformation to low-angle grain boundaries to form subgrains. This occurs due to dynamic recovery during laser powder bed fusion. The yield strength is successfully modelled via a Hall–Petch-type relationship in terms of the subgrain size, instead of the actual grain size or the dislocation cell size. The validated Hall–Petch-type equation for austenitic stainless steels provides a guideline for the strengthening of laser powder bed fusion alloys with subgrain refinement, via increasing the low-angle grain boundary fraction (grain boundary engineering). To obtain higher strength, dynamic recovery should be promoted as the main mechanism to induce low-angle grain boundaries. The dependency of yield stress on process parameters and alloy composition is quantitatively described.
KW - Grain refinement
KW - Laser powder bed fusion
KW - Mechanical properties
KW - Microstructure
KW - Stainless steel
KW - Austenite
KW - Austenitic stainless steel
KW - Dynamics
KW - Grain boundaries
KW - Grain size and shape
KW - Recovery
KW - Strengthening (metal)
KW - Yield stress
KW - Dislocation cells
KW - Dynamic recovery
KW - Grain boundary engineering
KW - Hall-petch
KW - Laser powders
KW - Low angle grain boundaries
KW - New approaches
KW - Powder bed
KW - Subgrains
U2 - 10.1016/j.matdes.2021.110246
DO - 10.1016/j.matdes.2021.110246
M3 - Journal article
VL - 212
JO - Materials and Design
JF - Materials and Design
SN - 0261-3069
M1 - 110246
ER -