The forming limit strains (FLSs) of zircaloy-4 sheets are studied. After having obtained the true stress–strain curve of zircaloy-4 using the weighted-average method, limit dome height (LDH) tests are performed to establish experimental FLSs. We summarize related theoretical forming limit curves (FLC) and discuss their limitations. Two finite element (FE) models are established for determining FLSs; an LDH test FE model for the negative minor strain sector, and a biaxial tensile FE model for the positive minor strain sector. The numerical FLSs are found to agree well with experimental data. Since the numerical FLC gives the strain at the onset of local thinning (whereas the experimental FLC provides the strain between local necking and ductile fracture), resulting FE FLS values are slightly lower than the experimental ones so that results can be regarded as conservative. Our FE approach substitutes the expensive and time-demanding experimental LDH tests.

The finite element method is used to simulate indentation with a 100 nm spherical indenter on Al/Pd multilayer thin films and Al and Pd monolayer thin films. The elastic/plastic properties of bulk Al and Pd and the material formulation are obtained by molecular dynamics simulations of tensile and indentation loadings. Hill's plasticity with isotropic hardening is found to best represent the stress–strain response of both bulk Al and Pd. The Pd monolayers appear the hardest and the Al monolayers the softest. The indentation hardness of both monolayered and multilayered films is found to increase with the indentation depth and appears independent of the layer order and thickness in the multilayer films. The hardness values determined by the finite element method simulations are close to those obtained using the well-known formula of Field and Swain. No hardness enhancement in very thin multilayered films (3–5 nm per layer) is evident, in contrast to experimental reports.

Some Fe-rich amorphous alloys of Fe–B–P–Si and Fe–B–P–Si–C systems were found to exhibit simultaneously good soft magnetic properties with high-saturation magnetization values near 1.7 T, which are higher than those for previously reported Fe-based amorphous and glassy alloys, in addition to rather good amorphous ribbon formability, good bending ductility, and rather high corrosion resistance. The corrosion resistance increased with increasing P content, accompanying by the increase in thermal stability of the amorphous phase. The decrease in the outer surface velocity of the wheel, which results in the increase of ribbon thickness, also causes an improvement of surface smoothness of the melt-spun amorphous alloy ribbons. The syntheses of new high-saturation Fe-based soft magnetic amorphous alloys without any other transition metals hold promise for future extension of Fe-based soft magnetic amorphous materials.

The formation of deformation and recrystallization textures has been investigated in a Ni7W alloy after heavy cold rolling and subsequent annealing at different temperatures. Cold rolling to a von Mises strain of 4.17 produced a mix of rolling texture that lies between classical brass- and copper-type rolling textures, with the fraction of S({123}<634>), brass({110}<112>), and copper({112}<111>) orientations being 33, 28, and 13%, respectively. The fraction of rolling texture for the deformed Ni7W alloy samples increased slightly during recovery, was then consumed significantly during recrystallization, and dropped to 22% after being annealed at 800 °C for 1 h. The fraction of cube({001}<100>) orientation increased to 26% after primary recrystallization, whereas other random orientations of 43% formed in the Ni7W alloy samples. Further annealing promoted cube grain growth, which lead to a significant strengthening of the cube texture and to a significant loss in high angle boundary (HAB). The fractions of cube texture and HAB of the Ni7W alloy substrate were 92.1 and 27.8%, respectively, after annealing at 1200 °C for 1 h.

The fracture behavior of precracked nanocrystals with grain size gradients is simulated using the molecular dynamics method. A large grain size gradient is found to elevate resistance to crack propagation and transform the fracture mode from intergranular to intragranular when the crack is obstructed by a coarse grain. But the intragranular crack is nipped in its bud due to the difficulty of intragranular fracture. However, intergranular fractures can be always kept in nanocrystals with a small grain size gradient. Both the Schmid factors for the slip systems of grains near the crack tip and the critical stress intensity factors are calculated, and energy partitioning is conducted to analyze the mechanisms behind this phenomenon. The research exhibits the key role of grain size gradient in improving the antifracture ability of nanocrystals.

The mechanical behavior of a Zircaloy-4 sheet as induced by a pulsed laser was studied with an accurately developed computational process that was validated with experiments. A modified Gaussian model of the heat source and the use of experimentally obtained thermal and mechanical properties of Zircaloy-4 in the computational process provided reliable simulation results of the phase transition and mechanical deformation of Zircaloy-4. A parametric study of the pulsed laser welding conditions of Zircaloy-4 was undertaken using the developed computational process. The analyzed parameters were the laser power, pulse duration, and pulse frequency. The simulation results revealed that the deformation was significantly dependent on the geometry of the molten zone and the heat-affected zone, which can be designed by the analyzed laser parameters.

The effects of Fe2B-grain orientation on microstructure and properties of bulk Fe2B intermetallic fabricated by directional and ordinary solidification techniques have been investigated. The results show that unidirectional solidified Fe2B intermetallic possesses a strong (002) texture in the transverse direction owing to the opposite unidirectional heat-squeeze effect while random Fe2B grains can be produced under ordinary solidification conditions. The nonoriented Fe2B intermetallic has the highest linear expansion coefficient of 13.04 × 10−6 °C−1 while the microhardness and fracture toughness of transverse Fe2B intermetallic in the (002) plane are larger than those of Fe2B with other grain orientations and their values are ∼18.72 GPa and 6.42 MPa·m1/2, respectively. Liquid zinc corrosion results indicate that unidirectional Fe2B intermetallic with long axis perpendicular to the direction of liquid zinc corrosion displays the best corrosion resistance to liquid zinc owing to its beneficial barrier effect. The FeB transition phase can naturally form and grow parabolically during liquid zinc corrosion.

Recent studies have shown that chemical immiscibility is important to achieve enhanced radiation tolerance in metallic multilayers as immiscible layer interfaces are more stable against radiation induced mixing than miscible interfaces. However, as most of these immiscible systems have incoherent interfaces, the influence of coherency on radiation resistance of immiscible systems remains poorly understood. Here, we report on radiation response of immiscible Cu/Fe multilayers, with individual layer thickness h varying from 0.75 to 100 nm, subjected to He ion irradiation. When interface is incoherent, the peak bubble density decreases with decreasing h and reaches a minimum when h is 5 nm. At even smaller h when interface is increasingly coherent, the peak bubble density increases again. However, void swelling in coherent multilayers with smaller h remains less than those in incoherent multilayers. Our study suggests that the coherent immiscible interface is also effective to alleviate radiation induced damage.

The effect of erosion speed on the interaction between erosion and corrosion of the Fe–3.5 wt% B alloy in a flowing zinc bath has been investigated using a rotating-disk technique. The total erosion–corrosion rate increases rapidly, whereas the pure erosion rate tends to increase linearly with an increase in erosion speed and with low damage. The increase in total erosion–corrosion rate is strongly dependent on erosion–corrosion interaction. During the erosion–corrosion process, the severe corrosion reaction roughens the surface by forming a loose corrosion layer and cracks in the anticaustic Fe2B skeleton, which eventually facilitates erosion. The micromechanical scouring effect of liquid zinc worsens corrosion by accelerating the removal of corrosion products and causing spallation of anticaustic Fe2B. An increase in erosion speed intensifies the micromechanical scouring effect of flowing zinc significantly. A strong erosion–corrosion interaction occurs at high erosion speed, which leads to a greater material loss rate.

The mechanisms of densification and creep were examined during spark plasma sintering (SPS) of alumina doped with a low and high level of zirconia or yttria, over a temperature range of 1173–1573 K and stresses between 25 and 100 MPa. Large additions of yttria led clearly to in situ reactions during SPS and the formation of a yttrium-aluminum garnet phase. Dopants generally lead to a reduction in the densification rate, with substantial reductions noted in samples with ∼5.5 vol% second phase. In contrast to a stress exponent of n ∼ 1 for pure alumina, the doped aluminas displayed n ∼ 2 corresponding to an interface-controlled diffusion process. The higher activation energies in the composites are consistent with previous data on creep and changes in the interfacial energies. The results reveal a compensation effect, such that an increase in the activation energy is accompanied by a corresponding increase in the pre-exponential term for diffusion.

This study modified the surfaces of three kinds of TiNi-based shape memory alloys (SMAs) by dry electrical discharge machining (EDM) in nitrogen (N2) and acetylene (C2H2) gas mixture. The effects of composition of the dielectric medium and work-piece on the machining performance and surface characteristics were investigated. Increasing the ratio of acetylene gas in gas mixture was beneficial for improving the material removal rate (MRR). However, adding a large amount of acetylene gas resulted in unstable discharge. A recast layer, comprising nitrides and carbides, which well adhered on the EDMed surface exhibited high hardness. Among Ti50Ni50, Ti50Ni49.5Cr0.5, and Ti40.5Ni49.5Zr10 SMA as a work-piece, Ti40.5Ni49.5Zr10 SMA has the lowest MRR owing to it possessed the highest melting temperature and thermal conductivity. The recast layer on Ti40.5Ni49.5Zr10 SMA, comprising zirconium nitride, exhibited the highest hardness and adhesion among all the SMAs. However, the high-hardness recast layer deteriorated the shape recovery of the SMA.

Lithium thio-phosphorus oxynitride glasses, LiPOSN, have been prepared by mechanical milling process from the mixture of Li2S and LiPON glass. The anionic substitution of oxygen by sulphur and nitrogen in the phosphate glass structure has been confirmed by 1D 31P solid state nuclear magnetic resonance and x-ray photoelectron spectroscopy. The study of thermal and electrical properties reveals a decrease in the glass transition temperature, likely due to the depolymerization of glass network by the decrease of bridging oxygens and sulphurs, along with a sharp increase in the ionic conductivity when lithium sulphide is incorporated into the oxynitride glasses. The improvement of chemical durability by the introduction of nitrogen, together with the increase in ionic conductivity up to values closed to the value of commercial LiPON thin film electrolyte, suggests that these LiPOSN glasses could be good candidates as solid electrolytes for lithium microbatteries.

This article addresses the metallurgical and mechanical properties of Nd:YAG laser welded Inconel 625 and duplex stainless steel SAF 2205. Keyhole plasma mode laser welding was adopted to obtain the joints. Microstructure studies showed slight grain coarsening at the heat affected zone of Inconel 625. Line mapping and elemental mapping analysis were carried out at the weld interface and in the fusion zone to examine the elemental migration as well as the composition of the phases present in these regions. The fusion zone microstructure showed the presence of Nb, Mo rich Laves phase segregated at the interdendritic arms. Tensile studies corroborated that an average joint strength of 820 MPa has been displayed by these weldments, which was almost equal to one of the parent metals, SAF 2205. It is evident from the charpy v-notch studies that the impact toughness of these laser weldments was found to be 10 J and this low toughness could be reasoned out to the formation of Mo rich phases. The structure–property relationships of these weldments have been addressed in detail and the outcomes of the study will be highly useful for marine and geothermal applications.

Oxidation of atomized Al–Mg–Li alloys with compositions ranging from Al0.85Mg0.1Li0.05 to Al0.55Mg0.4Li0.05 (wt%) was examined by thermogravimetry/differential thermal analysis. The results showed that oxidation proceeded in two steps. During the first step, lithium and magnesium were oxidized preferentially and removed from the metallic phase. The other step, during which the remainder of the metallic phase was oxidized, occurred over a wide range of temperature (989–1098 °C). The temperature of the second effect decreased slightly with increasing magnesium content from 10 to 30% in the alloy. For Al0.55Mg0.4Li0.05 alloy, the second exothermic peak occurred at 540 °C, and no exothermic peak was observed at higher temperature. The porous structure formed during the selective oxidation promotes the oxidation of residual Al in the alloy. Al0.55Mg0.4Li0.05 was oxidized completely at 1100 °C, lower than the temperature of other alloys. The thermite reaction experiment of Al0.55Mg0.4Li0.05–Fe2O3 system conducted in Ar showed a reaction temperature of 587 °C, significantly lower than the reaction temperature observed for Al–Fe2O3 system.

Microelectromechanical systems (MEMS) are increasingly at our fingertips. To understand and thereby improve their performance, especially given their ever-decreasing sizes, it is crucial to measure their functionality in situ. Atomic force microscopy (AFM) is well suited for such studies, allowing nanoscale lateral and vertical resolution of static displacements, as well as mapping of the dynamic response of these physically actuating microsystems. In this work, the vibration of a tuning fork based viscosity sensor is mapped and compared to model experiments in air, liquid, and a curing collagen gel. The switching response of a MEMS switch with nanosecond time-scale activation is also monitored – including mapping resonances of the driving microcantilever and the displacement of an overhanging contact structure in response to periodic pulsing. Such nanoscale in situ AFM investigations of MEMS can be crucial for enhancing modeling, design, and the ultimate performance of these increasingly important and sophisticated devices.

NiCrMoV steels used in nuclear rotor with heavy section were successfully fabricated by ultra-narrow gap submerged arc welding method. In this study, the mechanical properties including the tensile and impact toughness of the welded joints (WJs) with a wide temperature range were systematically investigated. Microstructural characterization indicated that the high-temperature tempered martensite and tempered bainite, as the main microstructure in WJ, were responsible for the improved comprehensive mechanical properties of the WJ. Microhardness across the WJ was measured as well, showing that the highest value of hardness occurred at the heat-affected zone which represents the appropriate lowest impact toughness of WJ. However, compared with the base metal, the ultimate tensile strength of the WJ displayed approximately equivalent values, while the yield strength was increased with increasing temperature. All the fracture of the WJ specimens occurred on the weld metal. In addition, the Charpy impact energy of weld metal was obtained at various temperatures, and the transition temperature (Tt) of welded metal was determined as 5 °C, which helps for the application design. The fractography indicated that the ductile fracture modes changed to quasi-cleavage ones gradually with decreasing temperature, and also the dimples became smaller and shallower.

Aluminum matrix composite with 10 wt% of MoO3 particulate reinforcement was synthesized through powder metallurgy technique. The cold upsetting studies of the composites were investigated based on Taguchi L9 orthogonal array experimental design to evaluate the significance of compaction pressure, sintering temperature, and sintering time on strength coefficient. The combination of 350 MPa pressure, 600 °C temperature, and 90 minutes sintering time was identified as the optimum blend for maximum strength coefficient using the main effect plot. From the analysis of variance, compaction pressure and sintering temperature were identified as highly contributing parameters on strength coefficient. Further, a confirmation test was also conducted with the optimum parameter for validation of the Taguchi results. X-ray diffraction and scanning electron microscopy were used to confirm the presence of MoO3 and its uniform distribution over the aluminum matrix.

The mechanical properties of ultrafine-grained aluminum produced by equal-channel angular pressing (ECAP) are strongly influenced by strain rate. In this work, an experimental investigation of local strain rate sensitivity as it relates to microstructure was performed using a combination of scanning electron microscopy and digital image correlation. Uniaxial tension tests were carried out at 200 °C and strain rates alternating between 2.5 × 10−5 s−1 and 3.0 × 10−3 s−1. The results demonstrate that the heterogeneous microstructure generated by ECAP has a strong effect on the microstructure scale strain rate sensitivity. Deformation centered at grain boundaries separating regions of banded microstructure exhibits the greatest strain rate sensitivity. Strain rate sensitivity is limited in deformation occurring in regions of microstructure composed of ultrafine grains separated by low-angle grain boundaries. The tensile specimens all failed by shear bands at 200 °C and at room temperature they failed by necking with little plastic deformation apparent outside of the neck.

The effect of surface preparation—grinding, polishing, and electrochemical etching—on the duplex stainless steel passive film conductivity was investigated by in situ current sensing atomic force microscopy. The current maps show that the current in the passive film on three prepared surfaces is different, especially for the ferrite and austenite phase surface. The current on the austenite and ferrite is similar on either mechanical ground or polished surfaces, but the current on the austenite surface is much higher than current on the ferrite surface after electrochemical etching. The difference in the passive film conductivity originates from the changes in the chemical composition and thickness of the passive film and the change in topographical properties induced by the preparation procedures. This is confirmed by AFM, x-ray photoelectron spectroscopy, and auger electron spectroscopy measurements.

Over the last decade, the inclusion of nanofeatures has been demonstrated extensively for improving the performance of thermoelectric materials. The continued approach is to nanofeaturing these materials in a smart manner tailoring their electronic and thermal response. This research provides a computational tool for predicting all parameters in the thermoelectric figure of merit for a Si/Ge superlattice structure as a function of doping and layer thickness. The approach involves coupling a nonequilibrium Green's function electronic and thermal transport model. The phonon description is communicated between the two models to facilitate spatially resolved multiphonon frequency electron–phonon scattering. Findings support the consideration of multiple phonon frequency scattering to accurately predict ZT values. An extrema in ZT as function of both doping and geometry were predicted. Furthermore, the optimal superlattice design was determined to be a Si(2 nm)/Ge(7 nm) with a donor concentration on the order of 1019 cm−3 for operation at 300 K.