Tantalum carbide (TaC) is an ultrahigh temperature ceramic, where low damage tolerance limits its potential application in propulsion sector. In this respect, current work focuses on enhancing the toughness of TaC based composites via synergistic reinforcement of SiC and carbon nanotubes (CNTs). Spark plasma sintering of TaC, reinforced with 15 vol% SiC and 15 vol% CNT (processed at 1850 °C, 40 MPa, 5 min), has shown enhanced densification from ∼93% (for TaC) to ∼98%. Potential damage of the tubular CNTs to flaky graphite was revealed using transmission electron microscopy, and was supplemented via Raman spectroscopy. SiC addition has enhanced the hardness to ∼19.5 GPa while a decreases to 12.6 GPa was observed with CNT addition when compared to the hardness of TaC (∼15.5 GPa). The increase in the indentation fracture toughness (from 3.1 MPa m1/2 for TaC to 11.4 MPa m1/2) and fracture strength (from ∼23 MPa for TaC to ∼183 MPa) via synergetic reinforcement of SiC and CNT is mainly attributed to energy dissipating mechanisms such as crack branching, CNT bridging, and crack-deflection. In addition, the reduction of interfacial residual tensile-stresses with SiC- and CNT-reinforcement, resulting an overall increase in the fracture energy and toughening, is also established.

Tribological performance of industrial applications involving boundary lubrication regime can be improved by depositing surface coatings such as diamond-like carbon (DLC) on the interacting surfaces. DLCs are considered as hard coatings with unique combination of properties which results in minimizing the friction induced energy and material losses especially under starved lubrication conditions. In spite of high wear-resistance and ultralow friction coefficients, there are a lot of factors that can directly influence the tribological characteristics of DLC coatings. Although, many studies were conducted to comprehend the effects of intrinsic/extrinsic conditions on tribological behavior of these coatings, still there is a lack of understanding due to contradictory remarks. Therefore, there is a need to rearrange the published data in an organized manner for logical continuation of research. In this paper, a brief introduction of DLC coatings is presented followed by detailed discussion on conditions that can directly influence their tribological properties.

Herein, Cu and Cu–Ge alloys with different stacking fault energies (SFEs) are prepared via rolling at room temperature (RTR) and via a combination of high-pressure torsion (HPT) and RTR (HPT + RTR). The x-ray diffraction measurements reveal that the grain size, dislocation density, and twin density vary with the strain and SFEs. The tensile tests indicate that the strength of materials with medium SFEs increases initially and then slightly declines, while the ductility is enhanced by increasing the strain via HPT. In contrast, for low-SFE materials, enhanced strength and improved ductility may be achieved simultaneously through increasing the strain to a high level. The variation of strength with respect to strain is primarily dependent on the solute concentration and SFE. The underlying mechanisms governing the effect of strain and SFE on the microstructures and mechanical properties of the metals are also discussed.

The microstructure, room temperature compressive property, and elevated temperature tensile property of directionally solidified NiAl–Cr(Mo)–(Hf,Dy) hypereutectic alloy were investigated. The directional solidifications of liquid metal cooling technique (LMC) and zone melted liquid metal cooling technique (ZMLMC) were adopted. In the LMC alloy, the well-aligned and fully eutectic lamellar structure parallel to the growth direction is obtained. The interlamellar spacing gradually decreases with increasing the withdrawal rate, and the compressive yield strength gradually increases. In the ZMLMC alloy, the eutectic lamellar structure is disordered and not parallel to the growth direction, and the quantities of Cr(Mo) primary phases are observed. Compared to the ZMLMC alloy, the LMC alloy has a better combination property because of the well-aligned lamellar structure. The observations of crack propagation and fracture surface are performed to better understand the fracture behavior.

Ti–47Al–1.0W–0.5Si (at.%) alloy was directionally solidified in the range of growth rate (V) (V = 3–100 μm/s) at a constant temperature gradient (G = 18 K/mm). It was found that α phase was the primary phase of the alloy. Both primary dendritic arm spacing (λ) and interlamellar spacing (λs) decreased with increase of the growth rate (V) according to the relationship of λ ∝ V −0.356 and λs ∝ V −0.49, respectively. The Solidification segregation occurred since the enrichment of the solute element W in primary α phase during solidification. The degree of the segregation increased with the increase of the growth rate (V). The results also revealed that the lamellar orientation was not always perpendicular to the growth direction (GD) because the GD of primary α dendritic deviated from the preferred $\left\langle {0001} \right\rangle$ direction. The microhardness increased with increasing growth rate (V) according to H V ∝ 289.5V 0.12 because of the microstructure refinement.

Bulk cementite samples with chromium (Cr) concentrations of 0, 3.01, 6.03, 8.22, and 9.76 wt% were prepared by mechanical alloying and spark plasma sintering. The elastic modulus, elastic recovery, and hardness increased with increasing chromium content. The maximum microhardness was 1070.74 HV (Vickers hardness) and the maximum elastic modulus was 199.32 GPa using a nanoindentation device. The effect of different concentrations of Cr on the wear behavior of the cementite plowing depth, roughness, debris from the worn surfaces, and weight loss due to wear were measured using pin-on-disk tribometric equipment. It was found that both the morphology and the abrasion resistance of a surface worn by microcutting and microplowing increased markedly with increasing Cr content.

The aim of the present work was to study the effect of the finishing rolling temperature on interpass recrystallization promotion of an Nb-stabilized AISI 430 steel, via torsion tests simulation of a Steckel mill. The occurrence of interpass recrystallization was investigated by interrupting the tests before predetermined passes and analyzing the samples via electron backscatter diffraction (EBSD). The results revealed that interpass recrystallization can be promoted by decreasing the initial hot rolling temperature; which results in increased strain hardening during the passes and therefore, increased stored energy for recrystallization. The torsion test results concurred with those obtained by EBSD measurements. Furthermore, an optimum temperature range of 900–840 °C was found to promote interpass recrystallization during hot rolling.

In this paper, numerical study was systematically conducted to analyze the shear banding evolution in bulk metallic glasses (BMGs) with various notches subjected to the uniaxial compression, and the relation between the notched configurations and compressive malleability was therefore elucidated. Free volume was used to be an internal state variable to depict the shear banding nucleation, growth and coalescence in the BMGs with the aid of free volume theory, which was incorporated into ABAQUS finite element method code as a user material subroutine. The present numerical procedure was firstly verified by comparing with the existing experimental data, and then parameter analysis was performed to discuss the impacts of notch shape, notch size, notch orientation, and notch configuration on the plastic deformability of notched samples. The present modeling will shed some light on the failure mechanisms and the toughening design of notched BMG structures in the engineering applications.

Synchrotron radiation real-time imaging technology was performed to in situ study the Cu–Ni cross-interaction in Cu/Sn/Ni solder joints under temperature gradient during soldering. The direction of temperature gradient significantly influenced the Cu–Ni cross-interaction. When Ni was the hot end, both Cu and Ni atoms could diffuse to the opposite interfaces, resulting in the occurrence of the Cu–Ni cross-interaction at both interfaces. The consumption of the Cu cold end was abnormally large, whereas that of the Ni hot end was limited. When Cu was the hot end, only Cu atoms could diffuse to the opposite interface, resulting in the occurrence of the Cu–Ni cross-interaction only at the cold end. The Cu hot end was seriously consumed, whereas the Ni cold end was still intact. The interfacial intermetallic compounds were always thicker at the cold end than at the hot end, especially at the Ni/Sn cold end. Cu imposed more damaging effect than Ni under temperature gradient. Based on the atomic fluxes, a model was proposed to discuss the effect of temperature gradient on the Cu–Ni cross-interaction and the interfacial reactions in the Cu/Sn/Ni solder joints.

In searching for a suitable semiconductor material for hydrogen production via photoelectrochemical water splitting, α-Fe2O3 received significant attention as a promising photoanode due to its band gap (∼2.1 eV), good stability, low cost, and natural occurrence. α-Fe2O3 thin films were prepared by economic and facile dip coating method and subsequently subjected to an anodic potential of 700 mV versus Ag/AgCl in 1M KOH for different anodization times (1, 10, and 900 min) under illumination. X-ray diffractometry revealed increase in crystallites size from ∼31 nm for nanoparticles in pristine state to ∼38 and 44 nm after anodization for 1 and 900 min, respectively. A clear positive correlation between anodization time and grain (particle) size was observed from field emission gun scanning electron microscopy and atomic force microscopy (AFM); longer exposure time to anodizing conditions resulted in larger grains. Grain size increased from ∼57.9 nm in pristine state to ∼153.5 nm after anodization for 900 min. A significant smoothening of the surface with increase in anodization time was evident from AFM analysis.