For decades, grain boundary engineering has proven to be one of the most effective approaches for tailoring the mechanical properties of metallic materials, although there are limits to the fineness and types of microstructures achievable, due to the rapid increase in grain size once being exposed to thermal loads (low thermal stability of crystallographic boundaries). Here, we deploy a unique chemical boundary engineering (CBE) approach, augmenting the variety in available alloy design strategies, which enables us to create a material with an ultrafine hierarchically heterogeneous microstructure even after heating to high temperatures. When applied to plain steels with carbon content of only up to 0.2 weight %, this approach yields ultimate strength levels beyond 2.0 GPa in combination with good ductility (>20%). Although demonstrated here for plain carbon steels, the CBE design approach is, in principle, applicable also to other alloys.

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Chemical boundary engineering: A new route toward lean, ultrastrong yet ductile steels.

Research in bioelectronics is highly interdisciplinary, with many new developments being based on techniques from across the physical and life sciences. Advances in our understanding of the fundamental chemistry underlying the materials used in bioelectronic applications have been a crucial component of many recent discoveries. In this review, we highlight ways in which a chemistry-oriented perspective may facilitate novel and deep insights into both the fundamental scientific understanding and the design of materials, which can in turn tune the functionality and biocompatibility of bioelectronic devices. We provide an in-depth examination of several developments in the field, organized by the chemical properties of the materials. We conclude by surveying how some of the latest major topics of chemical research may be further integrated with bioelectronics.

Recent advances in bioelectronics chemistry

Effect of Ti variation on microstructure evolution and mechanical properties of low carbon medium Mn heavy plate steel

Microstructure evolution and enhanced performance of a novel Nb-Mo microalloyed medium Mn alloy fabricated by low-temperature rolling and warm stamping

Deformation-induced martensitic transformation kinetics and correlative micromechanical behavior of medium-Mn transformation-induced plasticity steel

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

A novel application of quenching and partitioning (Q&P) treatment to warm stamping of a warm-rolled medium Mn steel was investigated. The results show that Q&P could improve yield strength of auto-parts from the formation of carbides and twinned martensite, and reduce the yield point elongation for carbon partitioning during Q&P process and a higher dislocation density. Regardless of stamping temperature either the single austenite or dual-phase region, an extraordinary product of strength and ductility (≥24 GPa·%) was achieved, which is two or three times higher than those of hot-stamped boron steels. The combined warm rolling and warm stamping process with Q&P treatment may have potential to implement the application of medium Mn steels for ultrahigh strength-ductile auto-parts.

Ultrahigh strength-ductile medium-Mn steel auto-parts combining warm stamping and quenching & partitioning

The deformation mechanisms of a novel Mn-based transformation/twinning induced plasticity (TRIP/TWIP) lightweight steel (10.12Mn-0.31C-3.81Al-0.56Si, wt.%) was investigated through the as-termed Mn preservation-cold rolling-intercritical annealing (PR-IA) route. A recrystallized equiaxed microstructure with fine and ultrafine-bimodal grain size distribution was obtained after IA at 800 °C, which exhibited an excellent balance of high ultimate tensile strength (UTS = 1048 MPa) and total elongation (TE = 63%). The bimodal-size distribution of austenite grains gave rise to the differences in the austenite stability, thus triggering the multi-stage TRIP effects (positive TRIP, slow TRIP effect) and the TWIP-coordinated TRIP effect in the entire tensile deformation. Activation of multi-stage strengthening mechanisms improved the strain hardening ability of the present medium Mn lightweight steel while maintaining its high tensile ductility.

Deformation mechanisms of a novel Mn-based 1 GPa TRIP/TWIP assisted lightweight steel with 63% ductility

This work investigates the correlation between microstructure and mechanical properties of a nano-precipitation strengthened ultra-low carbon (NPS- ULC) Ti–Mo–Nb steel. Two types of matrix microstructures (ferrite and martensite) with nano-precipitates were obtained through hot rolling and isothermal transformation in the case of ferrite, or by quenching and tempering, for martensite. The martensitic microstructure showed increases in both YS and UTS by ~110 and ~100 MPa, respectively, over the ferritic microstructure without sacrificing tensile ductility. All ferritic and martensitic specimens exhibited a two-stage work hardening behavior with different work hardening rates at high strain levels. Quantitative analysis of the strengthening contributions confirms that the increase in yield stress of the NPS-ULC specimens with a martensitic matrix was a result of the fine martensitic laths as well as the higher dislocation density and nano-precipitates.

Hongshou Huang

Papers

Microstructure evolution and enhanced performance of a novel Nb-Mo microalloyed medium Mn alloy fabricated by low-temperature rolling and warm stamping

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

Ultrahigh strength-ductile medium-Mn steel auto-parts combining warm stamping and quenching & partitioning

Deformation mechanisms of a novel Mn-based 1 GPa TRIP/TWIP assisted lightweight steel with 63% ductility

The effects of a ferritic or martensitic matrix on the tensile behavior of a nano-precipitation strengthened ultra-low carbon Ti–Mo–Nb steel