Strengthening mechanisms in directed energy deposited austenitic stainless steel
By Thale R. Smith, J. Sugar, C. San Marchi, J. Schoenung. Acta Materialia, 2019
283 citations recorded by the source corpus.
Abstract Microstructures and mechanical properties are evaluated in austenitic stainless steel structures fabricated by directed energy deposition (DED) considering the effects of applied loading orientation, build geometry, and distance from the deposition baseplate. Locations within an as-deposited build with different thermomechanical history display different yield strength, while those locations with similar history have approximately the same yield strength, regardless of test specimen orientation. Thermal expansion of deposited material near the baseplate is inhibited by the mechanical constraint imposed by the baseplate, promoting plastic deformation and producing a high density of dislocations. Concurrently, high initial cooling rates decrease away from the baseplate as the build is heated, causing an increased spacing of cellular solidification features. An analysis of strengthening mechanisms quantitatively established for the first time the important strengthening contribution of high dislocation densities in the materials (166–191 MPa) to yield strength that ranged from 438 to 553 MPa in the present DED fabricated structures. A newly adopted mechanistic relationship for microsegregation strengthening from the literature indicated an additional important contribution to strengthening (123–135 MPa) due to the cellular solidification features. These findings are corroborated by the measured evolution of microstructure and hardness caused by annealing the DED material. These results suggest that the mechanical properties of deposited austenitic stainless steels can be influenced by controlling thermomechanical history during the manufacturing process to alter the character of compositional microsegregation and the amount of induced plastic deformation.
Subfields: Aerospace Engineering, Mechanical Engineering
View Paper: https://www.semanticscholar.org/paper/963b8b7e3851c4ca731b0f7ab0bd5c70d1ba3797
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Citations in the corpus
- Selective laser melting enabling the hierarchically heterogeneous microstructure and excellent mechanical properties in an interstitial solute strengthened high entropy alloy (2019, background): “The internal stress induced during SLM can make a minor contribution to theσ y, while the strengthening effect of few oxides is negligibly small [15,24].”
- Grain refinement of stainless steel in ultrasound-assisted additive manufacturing (2020, background): “Experimental data from the literature [49-57] and this work on grain size d and primary spacing of cells λc of AM-fabricated 316L stainless steel are compiled in Table 2.”