Hot isotherm compression tests were performed in temperature range of 350–500 °C and at strain rates of 0.0005 to 0.5 s−1 for Al6061 alloy reinforced with alumina nanoparticles. Effect of deformation parameters and optimal conditions for hot working this nanocomposite were comprehended thoroughly via hot working data analyses, electron microscopy images, and X-ray diffractograms. The results indicated the severity of hot deformation process and an increase in the activation energy to 320 kJ/mol due to the addition of nanoparticles. Dynamic recovery (DRV) was considered as the individual determinative softening mechanism during hot deformation of this nanocomposite, and no sign of dynamic recrystallization (DRX) phenomenon observed in the same domain. The unstable region occurred at high strain rates and temperature range of 350–500 °C accompanied with happening drastic defects such as shear bands and cracks. Furthermore, the value of both critical strain and critical stress increased with increasing the strain rate and alumina addition. On the other hand, increasing the temperature decreased the value of critical strain and facilitated the initiation of softening mechanisms.

To clarify the effect of bainite in microstructure on hydrogen diffusion and trapping behavior and susceptibility to hydrogen assisted cracking of API grade linepipe steel, three specimens with different fraction of bainite in the microstructure are used. Firstly, hydrogen diffusion and trapping behaviors of the steels are studied by utilizing the electrochemical permeation technique. For fundamental analysis on the experimental data, a variety of diffusion parameters were determined by curve-fitting with a theoretical diffusion equation based on numerical finite difference method (FDM). It indicates that the steel with higher fraction of bainite exhibits much higher sub-surface hydrogen concentration and much lower apparent hydrogen diffusivity. This behavior can be understood by the fact that the steel containing higher fraction of bainite in the microstructure has higher concentration of reversible traps and consequent larger diffusible hydrogen, leading to much slower diffusion kinetics of hydrogen atoms. Consequently, the susceptibility to hydrogen induced cracking (HIC) and sulfide stress cracking (SSC) of the steel with higher fraction of bainite increases significantly.

A TiAlN coating was deposited on a YT14 cemented carbide cutting tool using a cathodic arc ion plating, the surface-interface morphologies, chemical elements, phases, and microhardness of the obtained TiAlN coating were analyzed with a field emission scanning electronic microscope, energy dispersive spectrometer, X-ray diffraction, and microhardness tester, respectively, and the coating surface roughness and grain scale were characterized with a atomic force microscope. The bonding strength of the coating was measured with a scratch tester, and the friction–wear properties were investigated with a reciprocation type fiction–wear tester. The results show that the bonding strength of the coating is 54.9 N, and the coating microhardness reaches 2724 HV. The average coefficient of friction of the coating is 0.59, the wear mechanism is abrasive wear and slight brittle fracture.

For Sn–Pb eutectic solder alloy, uniaxial tensile tests were conducted to dog-bone type specimens annealed at different temperatures (60–180 °C) and durations (2–48 h). Low strain rates ranging from 10−4 s−1 to 10−3 s−1 were applied to study the competition between creep and plasticity and also the rate dependent effect of annealing condition. It is found that the influence of annealing temperature on material properties is more than that of annealing duration. Higher temperature up to 180 °C generally leads to higher yield and ultimate stresses and ultimate strain of annealed specimens. The optimal annealing condition is suggested to be 180 °C for 6 h for stable and efficient improvements in both strength and ductility. By proposing a concise unified creep and plasticity constitutive model, the sensitivity to strain rate and annealing condition is quantified with consideration of both creep and hardening properties. Parameter calibration theoretically confirms the observed optimal annealing condition in experiments.

In this study, SiC particle reinforced Al2024 matrix composites were fabricated by powder thixoforming (PT). Meanwhile, 2024 alloys were fabricated by permanent mold cast (PMC) and PT, respectively, to reveal superiorities of PT technology over the traditional processing technologies and the resulting composite over the matrix alloy. The microstructures and mechanical properties of the three materials were comparatively investigated. The results indicated that both the PT materials possessed finer spheroidal primary particles and smaller eutectic concentration, but the PMC alloy comprised large equiaxed grains, continuously net-shaped eutectic structures, and many porosities. The mechanical properties of the PT alloy were significantly higher than those of the PMC alloy because of the enhanced compactness and work hardening, decreased eutectic concentration, and fine primary particles. The incorporation of SiCp to the PT alloy further brought improvements, the ultimate tensile strength (UTS), yield strength (YS), and hardness were increased by 29.3% (UTS = 388 MPa), 35% (YS = 297 MPa), and 46.8% (hardness = 122.6 HV), respectively. A strengthening model considering different strengthening mechanisms and SiCp failure was proposed and YS of composite could be exactly predicted.

A series of hot compression tests of medium carbon Cr–Ni–Mo-alloyed steel, 34CrNiMo steel, were conducted on a Gleeble-1500 thermal mechanical simulator, in a wide temperature range of 1173–1423 K and at a strain rate range of 0.002–5 s−1. Three constitutive models, namely the Johnson–Cook (JC) model, strain compensated Arrhenius model, and the physically based constitutive model, were established to describe the hot deformation of 34CrNiMo steel. A comparative study of the three models was investigated by comparing the accuracy of prediction of flow stress behavior. The results imply that the JC model is not able to adequately represent the high-temperature flow behavior with the existance of recovery and recrystallization. The Arrhenius-type model based on mathematics has a good prediction in the flow stress behavior in all strain ranges during the hot deformation. The physically based constitutive model gives a better prediction accuracy of the deformation behavior in both flow stress and deformation mechanism.

A well-designed hybrid welding process for resistance plug welding (RPW) was conducted based on TRIP980 high-strength steel and SPCC low-carbon steel. The effects of welding current, welding duration time, electrode pressure and filler diameter on the shear tensile failure loading of the joint were systematically investigated and the related optimal welding parameters were accordingly obtained. The microstructure and mechanical properties of the joint were subsequently analyzed. The experimental results indicated that the welding parameters of welding current, filler diameter, and welding duration time and electrode pressure influencing the shear tensile failure loading of the joint are quite vital. This kind of joint possesses a rounded rectangular nugget and transition region. The atomic diffusion results in the firm joint, the metallurgical bonding between filler and base material is realized through the RPW technique.

Macroporous ceramics having unique pore morphologies with ceramic bridges, unidirectional cellular pores, and bamboo-like cells were fabricated by freezing gels with ceramic powder and various gelatin contents. Varying gel strengths were found to be effective for control of the pore architecture from open to closed pore channels. The proposed process is a relatively simple and versatile way to produce tailored pore configurations via a gelation freezing route. In addition, the relationship between the microstructure and mechanical properties of the resulting ceramics was discussed using a multiscale modeling technique, in which a homogenization method was conducted with microscopic models created from three dimensional images, global stress distributions in macroscopic samples by finite element method and local stress distributions. The simulation results were relatively consistent with the experimental results. The multiscale modeling technique was thus confirmed to be a strong tool for the prediction of the mechanical responses of porous ceramics.

Phase separation of InxGa1−xN into Ga-rich and In-rich regions has been studied by electron energy-loss spectroscopy (EELS) in a monochromated, aberration corrected scanning transmission electron microscope (STEM). We analyze the full spectral information contained in EELS of InGaN, combining for the first time studies of high-energy and low-energy ionization edges, plasmon, and valence losses. Elemental maps of the N K, In M4,5 and Ga L2,3 edges recorded by spectrum imaging at 100 kV reveal sub-nm fluctuations of the local indium content. The low energetic edges of Ga M4,5 and In N4,5 partially overlap with the plasmon peaks. Both have been fitted iteratively to a linear superimposition of reference spectra for GaN, InN, and InGaN, providing a direct measurement of phase separation at the nm-scale. Bandgap measurements are limited in real space by scattering delocalization rather than the electron beam size to ∼10 nm for small bandgaps, and their energetic accuracy by the method of fitting the onset of the joint density of states rather than energy resolution. For an In0.62Ga0.38N thin film we show that phase separation occurs on several length scales.

Cellular elasticity is frequently measured to investigate the biomechanical effects of drug treatment, diseases, and aging. In light of the cellular viscosity property exhibited by filament actin networks, this study investigates the viscoelasticity alterations of the human hepatocellular carcinoma (SMMC-7721) cell subjected to fullerenol treatment by means of creep tests realized by atomic force microscopy indentation. An SMMC-7721 cell was first modeled as a sphere and then as a flattened layer with finite thickness. Both Sneddon’s solutions and the Dimitriadis model have been modified to adapt to the viscoelastic situation, which are used to fit the same indentation depth–time curves obtained by creep tests. We find that the SMMC-7721 cell’s creep behavior is well described by the two modified models and the divergence of parameters determined by the two models is justified. By fullerenol treatment, the SMMC-7721 cell exhibits a significant decrease of elastic modulus and viscosity, which is presumably due to the disruption of actin filaments. This work represents a new attempt to understand the alternation of the viscoelastic properties of cancerous cells under the treatment of fullerenol, which has the significance of comprehensively elucidating the biomechanical effects of anticancer agents (such as fullerenol) on cancer cells.

Wear resistance plays an important role to ensure the machining precision of machine tool using gray cast iron guide rail. Bio-inspired surfaces imitating the cuticle of desert scorpion and shell archetype with alternate units were prepared on gray cast iron using biomimetic coupling laser remelting in air and water. Samples consisting of striature bionic units with various distributions were examined under dry sliding condition using a home-made wear testing machine. It was found that samples with bionic units displayed better wear resistance than the untreated gray cast iron. While samples with bionic units processed in water by laser returned highest wear resistance in the short run, samples with alternatively distributed units (processed by laser) presented better wear resistance in the long run. However, to understand the stress distributions and the wear mechanism of the samples finite element method was used in this study. Based on the experimental evidences, a two-stage wear mechanism was proposed.

Polyurethane-based bioadhesive was synthesized with polyols derived from castor oil (chemically modified and unmodified) and hexamethylene diisocyanate with chitosan addition as a bioactive filler. The objective was to evaluate the effect of type of polyols with the incorporation of low-concentrations of chitosan on the mechanical and biological properties of the polymer to obtain suitable materials in the design of biomaterials. The results showed that increasing physical crosslinking increased the mechanical and adhesive properties. An in vitro cytotoxic test of polyurethanes showed cellular viability. The biocompatibility of the polyurethanes favors the adhesion of L929 cells at 6, 24, and 48 h. The polyurethanes showed bacterial inhibition depending on the polyol and percentage of chitosan. The antibacterial effect of the polyurethanes for Escherichia coli decreased 60–90% after 24 h. The mechanical and adhesive properties together with biological response in this research suggested these polyurethanes as external application tissue bioadhesives.

Biological hydrogel is important in drug delivery system and tissue engineering. In this paper, we prepared a series of biological hydrogels with N,O-carboxymethyl chitosan (CS) and oxidized safflower and ligusticum wallichii polysaccharide-II (oxidized SLWP-II). Morphological analysis indicated the N,O-carboxymethyl CS/oxidized SLWP-II hydrogels (CSLHs) had porous interior structures, pore diameter ranged from tens to hundreds of micrometers. In vitro release test showed, with proportion of N,O-carboxymethyl CS to oxidized SLWP increasing from 1:1 to 1:3, cumulative release of bovine serum albumin decreased from 99 to 82%. In vitro cytotoxicity study showed that the developed hydrogels were not cytotoxic during one week of culturing with WI-38 cells, and they have a role in promoting cell proliferation. So the N,O-carboxymethyl CS/oxidized safflower and ligusticum wallichii polysaccharide-II hydrogels might have potential application in the drug delivery system and tissue engineering.

The effect of peak shock stress on the incipient spallation damage in a cylindrical sample under sweeping detonation is presented. The free surface velocity curve was measured by photon Doppler velocimetry and the quantitative investigation of voids in a spalled sample was performed using X-ray computer tomography. The results revealed that the maximum volume and the mean volume of voids in the spalled sample increased with increasing shock stress. The sphericity of voids decreases with the increasing of shock stress. The rod voids were the result of the independent growth of voids along the grain boundaries in samples with lower shock stress, while the rod shaped voids in sample with higher shock stress were formed due to coalesce. The rod voids can be found in a cylindrical sample, while the voids in plate samples were in the shape of spheres or ellipsoids, and the difference of stress state induced by the curvature in the geometry of samples may be the main reason.

The two-phase Ni3Al and Ni3V intermetallic alloy laser clad on substrate of SUS304 was evaluated by hardness measurement, scanning electron microscopy, electron probe microanalyzer and transmission electron microscopy observations, focusing on the effect of post annealing after laser irradiation. The laser clad coating layer was diluted with approximately 5.4 at.% Fe and 1.6 at.% Cr stemming from the substrate. In the as-clad coating layer, the inhomogeneous eutectoid microstructure due to incomplete phase separation into two intermetallic phases Ni3Al and Ni3V took place. The hardness in the as-clad coating layer was lower than that in post annealed coating layers. In the coating layer annealed at 1553 K for 5 h, a dual two-phase microstructure composed of the primary cuboidal Ni3Al surrounded by the channel regions in which the major constituent is the Ni3V phase was observed, indicating that the complete eutectoid microstructure was developed. In the coating layer annealed at 1248 K for 24 h, the developed microstructure was lamellar-like one composed of the Ni3Al and Ni3V phases. The hardness in the coating layer annealed at 1248 K was the highest in the coatings observed in this study.

Natural rubber (NR) is expected to enhance impact strength of poly(lactic acid) (PLA). Because the polarity difference of NR and PLA leads PLA/NR blends having phase separation and poor mechanical properties, this research aimed to synthesize NR-graft-PLA (NR–PLA) via esterification of maleated NR (NR-MAH) with PLA. The role of NR–PLA used as a compatibilizer on mechanical and thermal properties of the PLA/NR blends was studied. Maximum grafted PLA level at 66.8% (w/w) was reached when NR-MAH was esterified with PLA [2/1 (w/w) PLA/NR-MAH] catalyzed by 0.05 M 4-dimethylaminopyridine at 140 °C. The addition of 5% (w/w) NR–PLA [36.6% (w/w) grafted PLA content] into PLA/NR blend [80/20 (w/w)] increased Izod impact strength of the neat PLA plate from 28.9 J/m to 62.7 J/m due to partial miscibility of blends attested by morphology analysis and Molau test. Hydrolytic degradation of PLA/NR blends with and without the addition of NR–PLA was also examined.

Microstructure and mechanical properties of Mg–0.43Nd–xY–0.08Zn–0.11Zr (x = 0, 0.03, 0.06, and 0.12 at.%) alloys were investigated. The results indicated that Mg24Y5 phase was formed in the as-cast Y-containing alloys, the grains were refined and the amount of needle-like Mg12Nd phase in the α-Mg grain interior was increased with increasing Y addition. After solution treatment, the Mg24Y5 phase and needle-like Mg12Nd phase nearly completely dissolved into the α-Mg matrix and long-rod-like Zn2Zr3 phase occurred. The amount of Zn2Zr3 phase was increased with increasing Y content after age treatment. Mg–0.43Nd–0.12Y–0.08Zn–0.11Zr alloy exhibited the best combination of strength and elongation in all conditions, especially in the temperature range of 200–300 °C, and an Arrhenius model was established to study the plastic flow behavior. The improvement in mechanical properties was attributed to the grain refining, solution strengthening and enhanced precipitation hardening of Zn2Zr3 phase and β-type phase.

The hydrogenation behavior of Ti–44Al–6Nb (at.%) alloy was studied at temperature range of 1373–1693 K, and the effect of hydrogen on hot deformability was tested on Gleeble-1500D thermo-simulation machine. It is found that the lnCH increases linearly with 1/T, and hydrogen content increases with increasing of hydrogen time and flow rate logarithmically. The positive heat of solution of hydrogen denotes that hydrogen absorption in TiAl alloys is an endothermic reaction. The results also show that hydrogen promotes the lamellar colony size and lamellar spacing because that hydrogen can promote the diffusion of elements. There is more residual B2 phase in the hydrogenated alloy revealing that hydrogen stabilizes the B2 phase during hydrogenation. The nanohardness and elastic modulus of the alloy are decreased from 4.4 and 213.5 GPa to 4.2 and 199.8 GPa after hydrogenation with 0.033 wt% H. Thermal simulation results show that the peak stress is decreased by 30% after hydrogenation with 0.033 wt% H which corresponds to decreasing the deformation temperature by about 50 K. This is attributed to hydrogen-promoted dynamic recrystallization and dislocation movement.

Precipitates and grain sizes in non-oriented silicon steel samples, which were hot-rolled (HR), continuously annealed (CA), and stress-relief-annealed (SA), were characterized using scanning electron microscopy (SEM) equipped with electron back-scattered diffraction. The average grain sizes of the HR, CA, and SA samples were 28, 46, and 46 μm, respectively. SEM observations revealed that the precipitates were mainly dispersed inside grains in the HR and the CA samples, but mainly at grain boundaries in the SA sample. The density of precipitates was highest in the SA sample and lowest in the HR sample. Precipitates at the grain boundaries, which were identified as manganese sulfides, were nearly spherical, their diameter ranging from 0.3 to 0.7 μm. We calculated the pining force exerted by grain-boundary precipitates and found that it outweighed the driving force of the grain growth that was controlled by boundary curvature.

This research article addresses the effect of fillers on the high-temperature corrosion behavior of AISI 347 weld joints. Multi-pass pulsed current gas tungsten arc welding was carried out on 6.67 mm thick plates of AISI 347 using three different fillers namely ER347, ER2553, and ERNiCrMo-3. The fusion zone microstructures of AISI 347 employing ER2553 and ERNiCrMo-3 exhibited columnar and dendritic grain growth; whereas vermicular delta ferrite was observed at the fusion zone of ER347 welds. Tensile studies showed that the weld employing ERNiCrMo-3 exhibited better tensile strength than the parent metal. High-temperature corrosion studies were carried out on the fusion zones by exposing the coupons to an aggressive, synthetic molten-salt incinerator environment containing 40% Na2SO4–40% K2SO4–10% NaCl–10% KCl at 650 °C for 50 cycles. The studies attested that the fusion zone employing ERNiCrMo-3 exhibited better corrosion resistance than the other two fillers used in the study. Spallation of oxides was witnessed due to the dissolution of Cr2O3 in the ER347 and ER2553 fusion zones. The hot corroded samples were characterized using surface analytical techniques.