Many traditional approaches for strengthening steels typically come at the expense of useful ductility, a dilemma known as strength-ductility trade-off. New metallurgical processing might offer the possibility of overcoming this. Here we report that austenitic 316L stainless steels additively manufactured via a laser powder-bed-fusion technique exhibit a combination of yield strength and tensile ductility that surpasses that of conventional 316L steels. High strength is attributed to solidification-enabled cellular structures, low-angle grain boundaries, and dislocations formed during manufacturing, while high uniform elongation correlates to a steady and progressive work-hardening mechanism regulated by a hierarchically heterogeneous microstructure, with length scales spanning nearly six orders of magnitude. In addition, solute segregation along cellular walls and low-angle grain boundaries can enhance dislocation pinning and promote twinning. This work demonstrates the potential of additive manufacturing to create alloys with unique microstructures and high performance for structural applications.

https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1443&context=ameslab_manuscripts

Additively manufactured hierarchical stainless steels with high strength and ductility

Fundamentals of Modern Manufacturing: Materials, Processes and Systems

https://research.birmingham.ac.uk/portal/files/45381603/Liu_et_al_Dislocation_network_in_additive_Materials_Today_2017.pdf

Dislocation network in additive manufactured steel breaks strength–ductility trade-off

Intragranular cellular segregation network structure strengthening 316L stainless steel prepared by selective laser melting

https://dr.ntu.edu.sg/bitstream/10356/80615/1/Xipeng%20Tan_Materials%20and%20Design%202016.pdf

Selective laser melting of stainless steel 316L with low porosity and high build rates

Transformation of austenite to duplex austenite-ferrite assembly in annealed stainless steel 316L consolidated by laser melting

Fracture toughness and toughening mechanisms in graphene platelet reinforced Si3N4 composites

Silicon nitride + 1 wt% graphene platelet composites were prepared using various graphene platelets (GPLs) as filler. The influence of the addition of GPLs on the microstructure development and on the fracture toughness of Si 3 N 4  + GPLs composites was investigated. The GPLs with thickness from 5 nm to 50 nm are relatively homogeneously distributed in the matrix of all composites, however overlapping/bundle formation of GPLs was found, containing 2–4 platelets as well. The single GPLs and overlapped GPLs are located at the boundaries of Si 3 N 4 , and hinder the grain growth and change the shape of the grains. The fracture toughness was significantly higher for all composites in comparison to the monolithic Si 3 N 4 with the highest value of 9.9 MPa m 0.5 for the composite containing the GPLs with smallest dimension. The main toughening mechanisms originated from the presence of graphene platelets, and responsible for the increase in the fracture toughness values are crack deflection, crack branching and crack bridging.

Microstructure and fracture toughness of Si3N4 + graphene platelet composites

Defects-tolerant Co-Cr-Mo dental alloys prepared by selective laser melting.

An austenitic stainless steel was prepared by laser melting. High resolution transmission electron microscopy with energy dispersive spectrometry confirmed the in situ formation of oxide nanoinclusions with average size less than 50 nm. Scanning electron microscopy examination revealed the homogeneous dispersion of the oxide nanoinclusions in the steel matrix. The tensile and yield strengths of the prepared specimens were 703 and 456 MPa respectively with high ductility which is significantly improved compared to its conventionally casted counterpart.

/pdf/austenitic-stainless-steel-strengthened-by-the-in-situ-lmfxr32327.pdf

Lenka Kvetková

Papers

Transformation of austenite to duplex austenite-ferrite assembly in annealed stainless steel 316L consolidated by laser melting

Fracture toughness and toughening mechanisms in graphene platelet reinforced Si3N4 composites

Microstructure and fracture toughness of Si3N4 + graphene platelet composites

Defects-tolerant Co-Cr-Mo dental alloys prepared by selective laser melting.

Austenitic stainless steel strengthened by the in situ formation of oxide nanoinclusions