Impact of W alloying on microstructure, mechanical property and corrosion resistance of face-centered cubic high entropy alloys: A review

Face-centered cubic (f.c.c.) high entropy alloys (HEAs) are attracting more and more attention owing to their excellent strength and ductility synergy, irradiation resistance, etc. However, the yield strength of f.c.c. HEAs is generally low, significantly limiting their practical applications. Recently, the alloying of W has been evidenced to be able to remarkably improve the mechanical properties of f.c.c. HEAs and is becoming a hot topic in the community of HEAs. To date, when W is introduced, multiple strengthening mechanisms, including solid-solution strengthening, precipitation strengthening (μphase,σphase, and b.c.c. phase), and grain-refinement strengthening, have been discovered to be activated or enhanced. Apart from mechanical properties, the addition of W improves corrosion resistance as W helps to form a dense WO_(3) film on the alloy surface. Until now, despite the extensive studies in the literature, there is no available review paper focusing on the W doping of the f.c.c. HEAs. In that context, the effects of W doping on f.c.c. HEAs were reviewed in this work from three aspects, i.e., microstructure,mechanical property, and corrosion resistance. We expect this work can advance the application of the W alloying strategy in the f.c.c. HEAs.

Effect of silicon and prior deformation of austenite on isothermal transformation in low carbon steels

Isothermal transformation （TTT） behavior of the low carbon steels with two Si contents （0.50 wt pct and 1.35 wt pct） was investigated with and without the prior deformation. The results show that Si and the prior deformation of the austenite have significant effects on the transformation of the ferrite and bainite. The addition of Si refines the ferrite grains, accelerates the polygonal ferrite transformation and the formation of M/A constituents, leading to the improvement of the strength. The ferrite grains formed under the prior deformation of the austenite become more homogeneous and refined. However, the influence of deformation on the tensile strength of both steels is dependent on the isothermal temperatures. Thermodynamic calculation indicates that Si and prior deformation reduce the incubation time of both ferrite and bainite transformation, but the effect is weakened by the decrease of the isothermal temperatures.

Enhanced strength-ductility synergy via high dislocation density-induced strain hardening in nitrogen interstitial CrMnFeCoNi high-entropy alloy

The present work demonstrates that nitrogen doping inhibits the formation of deformation twins in a CrMnFeCoNi high entropy alloy,while significantly increases the strength without sacrificing much duc-tility at 77 K.Microstructural characterization and first-principles calculations were employed to unveil the role of interstitial nitrogen atoms in obtaining such an excellent combination of strength and ductility at 77 K.It is found that nitrogen addition increases generalized stacking fault energy(GSFE)and reduces twinning.However,the pinning of dislocations by nitrogen atoms effectively suppresses dislocation cross-slip and dynamic recovery and in turn,promotes the accumulation of dislocations.The high dislocation density induces a high strain hardening capacity and improves uniform elongation,which compensates for the ductility loss accompanied by solid solution strengthening.The effect of nitrogen doping enriches the design concept of high-and medium-entropy alloys,providing an economical and effective strategy to develop ultra-high-performance alloys that are suitable for cryogenic applications.

Enhanced tensile properties of a reversion annealed 6.5Mn-TRIP alloy via tailoring initial microstructure and cold rolling reduction

The feasibility of improving the overall performance of medium Mn steels was demonstrated via tailoring the initial microstructure and cold rolling reduction. The combined effects of cooling patterns after hot rolling （HR） and cold rolling （CR） reductions show： （1） as the cooling pattern varied from furnace cooling （FC） to oil quenching （OQ）, the intercritically annealed microstructure was dramatically refined and the fraction of recrystallized ferrite dropped, regardless of CR reductions. This resulted in both high yield/ultimate tensile strengths （YS/UTS） but low total elongation to fracture （El）; （2） as the CR reduction increased from 50% to 75%, the OQ-samples after annealing exhibited a more refined microstructure with relatively higher fractions of retained austenite and sub-structure, leading to higher YS and UTS but lower El; whereas the FC samples appeared to exhibit little difference in overall tensile properties in both cases. The differences in microstructural evolution with cooling patterns and CR reductions were explained by the calculated accumulated effective strain （eAES）, which was considered to be related to degrees of recovery and recrystallization of the deformed martensite （α＇）. The optimal tensile properties of -1 GPa YS and -40 GPa.% UTSxEI were achieved in the OQ-50%CR annealed samples at 650 ℃ for 1 h. This was quite beneficial to large-scale production of ultra-high strength steels, owing to its serious springback during heaw cold working.

Experimental and Simulation Study on Shielding Performance of Developed Hydrogenous Composites

Space radiation has been well-known as the main health hazard to crews involved in manned space explorations.Two kinds of hydrogenous-rich composites are developed through compressing molding under high-temperature processing techniques for shielding space radiation.Beams of 80~400 MeV/n ^(12)C of the Heavy Ion Research Facility in Lanzhou are used to test the shielding properties of the new composites.Experimental results show that the composite with more hydrogen content has higher shielding ability for 80 and 400 MeV/n ^(12)C particles.Meanwhile,the addition of boron has no obvious effect on improving the shielding performance of the composite.Monte Carlo radiation transport codes were used to assess the shielding performance of composite in real space radiation.The simulation results show that hydrogenous-rich composite has significant advantage in space radiation shielding compared with traditional aluminum.