An anti-embrittlement roadmap: Hydrogen is important for energy applications such as fuel cells but tends to diffuse into materials and make them more susceptible to fracture. Chen et al. tackled the challenge of identifying the exact location of hydrogen atoms in two common steels. The light weight and high mobility of hydrogen creates serious problems with conventional techniques. The authors used cryo-transfer atom probe tomography to show that hydrogen is pinned to various interfaces in the steels. This direct look into hydrogen trapping should help with the development of materials that are more resistant to hydrogen embrittlement. Science , this issue p. 171

This paper aims to investigate the unique substructure and grain growth of 316L stainless steel processed by selective laser melting (SLM) and clarify the mechanism. Results showed that the grain orientation on the x-z plane parallel to the build direction was the same type as the y-z plane, which all grow along the heat flow direction to form elongated columnar grains passing through the multi-layer fusion line. The epitaxial growth direction of grains changed abruptly with the vary of temperature gradient direction. Moreover, to expound the substructure formation based on solidification theory, a finite element model was established to obtain the distribution map of cooling rate G × R and solidified morphology G/R.

Fused Filament Fabrication (FFF) technology is used to create metal parts in this paper. A binder formula is developed for 316L stainless steel powder, composed of polypropylene (PP), styrene ethylene butylene styrene (SEBS) and paraffin wax (PW). The binder is mixed with the 316L stainless steel powder to produce mixture which is then extruded into filament. The optimum binder formula, PP:SEBS:PW = 5:2:2, is obtained by orthogonal experiment. After optimization, mixture viscosity is reduced, filament tensile strength is guaranteed, rigidity is improved. The filament can be printed by a desktop FFF printer to obtain green parts. Binder within the green parts can be sufficiently removed by solvent and thermal debinding, and the shape of printed parts can be maintained well. After sintering, shrunken 316L stainless steel parts can be created, some pores distributed inside. With finer metal powder, the relative density of sintered part can be increased to 96%. The research ideas of this paper can provide effective methods for the development and optimization of binder.

In the present study, we design a novel hot stamping steel containing high amounts of C and Si and micro-alloying element (i.e. Nb). The steel was subjected to quenching and partitioning (Q&P) process. The new Q&P treated hot stamping steel exhibits a significantly improved mechanical property in terms of strength, ductility and impact toughness compared with the traditional 22MnB5 hot stamping steel. The influence of partitioning time on the microstructure and mechanical properties was investigated. The retained austenite (RA) fraction and the carbon content of RA significantly increased with higher partitioning times. With increasing partitioning time, the uniform elongation, total elongation, strength-ductility balance and impact energy was also remarkably enhanced. The maximum strength-ductility balance achieves around 23 GPa %.