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Plain medium carbon steel with multiscale ferrite (α) + cementite (θ) lamellar structure was produced by warm rolling and subsequently annealing. The effect of annealing time on microstructural evolution was studied via scanning electron microscope and electron backscatter diffraction. The obtained results showed that the feature of multiscale lamellar microstructure remained virtually the same with annealing times from 10 to 60 minutes, while the increase of annealing time destabilizes the stability of the microstructure. The specimen annealed for 30 minutes demonstrated good combination of strength and ductility because of the improvement of strain strengthening ability. The strain hardening behavior was described by instantaneous strain hardening exponent ( $$ n_{i} $$ ) and modified Crussard–Jaoul (C–J) model. Furthermore, the respective strengthening contribution of grain refinement, sub-grain strengthening and cementite particles to the yield strength was investigated in detail.

High-entropy alloys (HEAs) exhibit unique microstructural features and properties in nanoscale and atomic scale because of their multi-element alloy system. The nanoscratching behaviors of three HEAs with different phase constituents, relative to the microstructure and mechanical properties of the HEAs, were investigated. Three typical phase constituents were selected: face-centered cubic (FCC) structure, body-centered cubic (BCC) structure, and a dual-phase structure containing both FCC and BCC phases. Despite the fact that the FCC alloy has the highest ductility and strain hardening capability, it exhibited inferior scratch resistance due to the over-softening of hardness. Due to the brittle failure mode, the BCC alloy hardly exhibited desirable scratch resistance despite its highest hardness. By contrast, the nanostructured dual-phase alloy exhibited the best scratch resistance because of its good combination of strength and ductility, as well as the ductile failure mode. This research suggests that the HEA with structure comprising nanoscale hard and soft phases is desirable for nanoscratch resistance, and possesses appropriate hardness for industrial applications.

Surface mechanical attrition treatment (SMAT) was carried out on hot-rolled AZ31 Mg samples along two orthogonal directions; as a result, two types of gradient structures with different grain sizes and texture components in different layers were produced. The tension–compression yield asymmetry (YA) was studied using samples with different thicknesses, in order to elucidate the effect of combinations of variable deformation modes operating in different layers of the two oriented SMAT samples. The 0° oriented SMAT sample containing layers with strong basal texture displayed significant YA, because of either dislocation slip or extension twinning domination during tension or compression. By contrast, the 90° oriented SMAT sample containing layers with coexisting orthogonal texture components had an obviously weakened YA, which was attributed to the multi-deformation modes cooperating during tension or compression, i.e., extension twinning or detwinning in conjunction with dislocation slips, leading to close yield stresses compared between tension and compression.

Surface mechanical attrition treatment (SMAT) was employed to produce gradient structures in AZ31B Mg alloy samples with two different initial textures. The structure of both samples can be regarded as an integration of two main layers: the severely deformed layer exhibited dramatic grain refinement to nano- and submicron-scale with weakened and randomized textures; the less deformed layer exhibited the inherited coarse grains with increased dislocation density, possessing the similar texture with the sample prior to SMAT. All the samples containing different layer constituents cut from the SMAT alloys showed remarkable increase of strength compared to the original Mg alloy. However, the two integral SMAT samples with different initial textures exhibited marked difference in uniform elongation (UE) during tension. That was attributed to the different strain hardening behaviors influenced by the deformation coordination and strain partitioning between layers with different orientation relationships. The 0° oriented SMAT sample showed no macroscopic strain transfer or slip transmission across layers, which was hard to cause dislocation accumulation throughout the whole thickness of the layered sample. That resulted in a limited strain hardening and UE. However, the favored orientation relationship between layers of the 45° oriented SMAT sample facilitated the strain transfer and slip continuity across the layers. That generated a dynamically migrating interface during tension, which allowed the dislocations accumulating over the whole sample volume. This caused a pronounced strain hardening and sustained UE to an appreciable value.

This work investigates the in situ capacitive charging/discharging process of a carbon cloth surface under an external mechanical strain in order to understand the strain-modulated electrochemistry of an amorphous material. Our work first quantifies the electrochemical change in capacitive potential, E, in response to an applied linear strain, ε. The experimental data show that tensile strain could positively shift the capacitive potential. More importantly, the discharging time, a significant representative parameter of the energy storage performance of a material, is shortened when mechanically stretched. This phenomenon suggests that the specific capacitance is strain-dependent, and tensile strain decreases the specific capacitance of carbon cloth. This dependence could be attributed to a change in the surface free energy of carbon cloth when it is mechanically stretched. External mechanical work can modulate the typical capacitive process on not only metal or metal-oxide surfaces with specific lattice structures but also the surfaces of amorphous materials. Keywords: Strained carbon cloth, Solid-liquid interface, Surface energy, Mechanical work

Metal/reinforcement nanolayered composites can effectively balance the strength and toughness. However, the difficulty of inserting nanoscaled metal layers restricts their practical application. In this study, laminated carbon nanotubes (CNTs) reinforced Cu composites with microscaled metal layered were fabricated by a feasible method and exhibited simultaneously enhanced strength and toughness. CNTs were deposited on Cu foils by electrophoretic deposition with two-dimensional homogeneous dispersion. Insertion of CNTs induced the laminated Cu composite with repeated layer spacing of ∼20 μm through hot pressing and hot rolling. Simultaneously enhanced yield strength (183 MPa) and elongation (30.9%) were obtained with only 0.067 vol% CNTs. The strength improvement reached far beyond the mixture rule in metal matrix composites (MMCs) with homogeneous CNTs dispersion. CNTs and the induced interfaces serve as effective dislocations motion barriers and strengthen the composite. Laminated composite exhibited more stable deformation due to suppressed strain location by the layered structure. This work highlights the strengthening and toughening effects of laminated structure induced by CNTs, and provides a feasible method to build the laminated MMCs with adjustable metal layer thickness and CNTs amount, thus breaking the dimensional limit of metal layers in the design of laminated MMCs with enhanced mechanical properties.

In this study, three grain-oriented silicon steels with different Nb contents were designed to investigate the effect of Nb on the behaviors of inhibitor solution and precipitation by Thermo-Calc software combined with TEM technology. The influence of Nb on precipitation rate of inhibitors in the silicon steels was also discussed. The results show that besides MnS and AlN, Nb(C,N) also exists in Nb-containing silicon steels, and with the increase of Nb content, the precipitation temperature and maximum mole fraction of Nb(C,N) increases significantly. Different Nb contents have no obvious effect on MnS. While the precipitation temperature of AlN decreases from 1190 °C to 1140 °C with Nb addition from 0.044wt% to 0.09 wt%, but the maximum mole fraction of AlN does not change. According to the PTT (Precipitation-Time-Temperature) curve, Nb addition accelerates the precipitation process of second phase particles and shortens the incubation period. Combining the theoretical calculations with TEM analyses, it is known that proper Nb addition in the silicon steel can reduce the slab reheating temperature. Whereas, with excessive Nb addition, the inhibitors can not dissolve into the matrix totally at 1250 °C, which will have a negative effect on the production of grain-oriented silicon steel.

A medium-carbon steel was processed through different warm rolling techniques, and the microstructural features with bimodal grain size distribution were found to be different. The combination of strength and ductility was ameliorated in the steel processed through warm rolling characterized by biaxial reduction. The enhanced strength is attributed to the densely distributed fine intragranular cementite particles and the small grain size in the coarse grain regions. The enhanced uniform elongation is due to the improved work hardening behavior at the large-strain stage. This work hardening behavior is predominantly ascribed to the finely dispersed intragranular particles. The relatively small grain size with nearly equiaxed shape in the coarse grain regions helps stabilize the uniform deformation to a large strain.