Ultrastrong and ductile synergy of additively manufactured H13 steel by tuning cellular structure and nano-carbides through tempering treatment

Microstructural evolution and mechanical properties of H13 steel fabricated by selective laser melting (SLM) with subsequent tempering treatment were systematically examined. It was found that the microstructure of the as-SLMed H13 samples consisted of cellular structures, lath martensite and high-volume fraction of retained austenite. After tempering at 600 °C for 1 h, the nanoscale Cr23C6 particles were detected at the boundaries of the partially dissolved cellular structures. The fine grains, the retained cellular structures, and the formation of Cr23C6 carbides significantly improved the mechanical properties of the H13 steel. A superior mechanical properties, including the yield strength (YS) of 1647 ± 29 MPa, ultimate tensile strength (UTS) of 2013 ± 35 MPa and elongation (El) of 4.1 ± 0.3% have been achieved in the SLMed H13 steel after tempering at 600 °C for 1 h. With the increase of tempering temperature to 700 °C, the cellular structures were completely dissolved and the high number density of coarse Cr23C6 carbides were formed, which led to the decrease of UTS at 1083 ± 21 MPa, while the elongation was significantly improved to 12.3 ± 1.2% due to the recovery of dislocation density and the decomposition of martensite in the H13 steel

Microstructure and mechanical properties of pseudo binary eutectic Al–Mg2Si alloy processed by laser powder bed fusion

The traditional wrought Al–Mg–Si alloys fabricated via laser powder bed fusion (LPBF) are prone to hot cracks, unless adding grain refiners in as-LPBFed Al alloys. In this work, the Al-9.6 wt.%Mg-4.9 wt.%Si (equivalent to pseudo binary eutectic Al-13.3 wt.%Mg2Si) alloy with low solidification range and hot-cracking susceptibility was successfully processed by LPBF. The as-LPBFed alloys have reached a high relative density of 99.3% at the VED of 129.6 J/mm3. The microstructures were featured by fine α-Al grains and cellular eutectic Mg2Si, accompanied by a high number density of dislocations, coherent GP zone and α-Al12(Fe,Mn)3Si phases. The as-LPBFed Al-13.3Mg2Si alloy exhibited the high ultimate tensile strength of 557 MPa, yield strength of 439 MPa and elongation of 2.9%. In addition to the grain refinement and dislocation strengthening, the strength enhancement is mainly ascribed to the dispersion strengthening from the divorced nanosized eutectic Mg2Si. The results demonstrate that manipulation of alloys at near eutectic composition is effective to achieve high strength Al–Mg–Si alloys processed by LPBF

High-strength Al–5Mg2Si–2Mg–2Fe alloy with extremely high Fe content for green industrial application through additive manufacturing

Achieving superior mechanical properties of Al alloys with high content of Fe impurities is very challenging. Here, a feasible method was applied to accommodate high Fe content (∼2.2 wt.%) and obtain superior strength in an Al–5Mg2Si–2Mg–2Fe alloy by using additive manufacturing. Heterogeneous distribution of Fe, including a high number density of α-Al12(Fe,Mn)3Si particles distributed at the melting pool boundary and excessive Fe segregated along the cell boundaries that divided by Mg2Si eutectics, was verified as the beneficial factor for the alloy design and strength enhancement. In addition to the heterogeneous grains that contain fine cells, the interactions between dislocations and coherent Mg2Si eutectics and the α-Al12(Fe,Mn)3Si particles played an important role in improving the mechanical properties. This work represents a breakthrough in recycling high-strength Al alloys with extremely high Fe doping for green industrial application through additive manufacturing

Microstructures and Mechanical Properties of H13 Tool Steel Fabricated by Selective Laser Melting

H13 stool steel processed by selective laser melting (SLM) suffered from severe brittleness and scatter distribution of mechanical properties. We optimized the mechanical response of as-SLMed H13 by tailoring the optimisation of process parameters and established the correlation between microstructure and mechanical properties in this work. Microstructures were examined using XRD, SEM, EBSD and TEM. The results showed that the microstructures were predominantly featured by cellular structures and columnar grains, which consisted of lath martensite and retained austenite with numerous nanoscale carbides being distributed at and within sub-grain boundaries. The average size of cellular structure was ~500 nm and Cr and Mo element were enriched toward the cell wall of each cellular structure. The as-SLMed H13 offered the yield strength (YS) of 1468 MPa, the ultimate tensile strength (UTS) of 1837 MPa and the fracture strain of 8.48%. The excellent strength-ductility synergy can be attributed to the refined hierarchical microstructures with fine grains, the unique cellular structures and the presence of dislocations. In addition, the enrichment of solute elements along cellular walls and carbides at sub-grain boundaries improve the grain boundary strengthening

High-strength Al–5Mg₂Si–2Mg–2Fe alloy with extremely high Fe content for green industrial application through additive manufacturing

Achieving superior mechanical properties of Al alloys with high content of Fe impurities is very challenging. Here, a feasible method was applied to accommodate high Fe content (∼2.2 wt.%) and obtain superior strength in an Al–5Mg2Si–2Mg–2Fe alloy by using additive manufacturing. Heterogeneous distribution of Fe, including a high number density of α-Al12(Fe,Mn)3Si particles distributed at the melting pool boundary and excessive Fe segregated along the cell boundaries that divided by Mg2Si eutectics, was verified as the beneficial factor for the alloy design and strength enhancement. In addition to the heterogeneous grains that contain fine cells, the interactions between dislocations and coherent Mg2Si eutectics and the α-Al12(Fe,Mn)3Si particles played an important role in improving the mechanical properties. This work represents a breakthrough in recycling high-strength Al alloys with extremely high Fe doping for green industrial application through additive manufacturing.</p

Strengthening CoCrNi medium-entropy alloy by tuning lattice defects

National Natural Science Foundation of China; Innovation Driven Program of Central South Universit