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The purpose of this paper is to investigate the effects of electric current stressing on damping properties of Sn5Sb solder.

Uniformly shaped Sn5Sb solders were prepared as samples. The length, width and thickness of the samples were 60.0, 5.0 and 0.5 mm, respectively. The damping properties of the samples were tested by dynamic mechanical analyzer with a cooling system to control the test temperature in the range of −100 to 100°C. Simultaneously, electric current was imposed to the tested samples using a direct current supply. After tests, the samples were characterized using scanning electron microscope, electron backscatter diffraction and transmission electron microscope, which was aimed to figure out the damping mechanism in terms of electric current stressing induced microstructure evolution.

It is confirmed experimentally that the increase in damping properties is due to Joule heating and athermal effects of current stressing, in which Joule heating should make a higher contribution. G–L theory can be used to explain the damping properties of strain amplitude under current stressing by quantitative description of geometrically necessary dislocation density. While the critical strain amplitude and high temperature activation energy decrease with increasing electric current.

These results provide a new method for vibration reliability evaluation of high-temperature lead-free solders in serving electronics. Notably, this method should be also inspiring for the mechanical performance evaluation and reliability assessment of conductive materials and structures serving under electric current stressing.

In terms of continuum mechanics a twin is represented by the sudden appearance of a shear eigenstrain state in a distinct region. The corresponding elastic strain energy, the interface energy and the energy dissipated due to the irreversible character of the deformation process are investigated. If the total amount of these energy terms, spent by the twinning process, can be provided by the interaction energy of an external and/or internal stress state with respect to the twin shear eigenstrain, then either a deformation twin band or a twin nucleus may appear. Realistic estimations of the dimensions of deformation twins can be presented. This energetic interpretation of twinning is experimentally demonstrated for intermetallic TiAl.

The purpose of this study is to investigate the manufacturability of Fe-3Si lattice structures and the resulting mechanical properties. This study could lead to the successful processing of squirrel cage conductors (a lattice structure by design) of an induction motor by additive manufacturing in the future.

The compression behaviour of two lattice structures where struts are arranged in a face-centred cubic position and vertical edges (FCCZ), and struts are placed at body-centred cubic (BCC) positions, prepared by laser powder bed fusion (LPBF), is explored. The experimental investigations are supported by finite element method (FEM) simulations.

The FCCZ lattice structure presents a peak in the stress-strain curve, whereas the BCC lattice structure manifests a plateau. The vertical struts aligned along the compression direction lead to a significant increase in the load-carrying ability of FCCZ lattice structures compared to BCC lattice structures. This results in a peak in the stress-strain curve. However, the BCC lattice structure presents the bending of struts with diagonal struts carrying the major loads with struts near the faceplate receiving the least load. A high concentration of geometrically necessary dislocations (GNDs) near the grain boundaries along cell formation is observed in the microstructure.

To the best of the authors’ knowledge, this is the first study on additive manufacturing of Fe-3Si lattice structures. Currently, there are no investigations in the literature on the manufacturability and mechanical properties of Fe-3Si lattice structures.

The purpose of this paper is to determine if the nanoindentation technique is a reliable method and whether it can be used to measure the surface hardness (H) in friction stir welded aluminum alloys. In order to test the reliability of nanoindentation technique, nanohardness values for friction stir welded aluminum alloys were compared to microhardness values. Additionally, the onset of plasticity (yielding) is investigated.

Nanoindentation experiments were performed for the determination of onset on plasticity (yielding) and comparison of local mechanical properties of both welded alloys. In order to test the reliability of nanoindentation technique, nanohardness values for friction stir welded AA6082 were compared to microhardness values. The specimen was tested using two different instruments – a Vickers microhardness tester and a nanoindenter tester for fine scale evaluation of H.

The results of this study indicate that nanohardness values with a Berkovich indenter reliably correlate with Vickers microhardness values. Nanoindentation technique can provide reliable results for analyzing friction stir welded aluminum alloys. The welding process definitely affects the material mechanical properties.

Microhardness and nanohardness obtained values can be correlated carefully, regarding the similarities and the differences of the two above mentioned techniques.

As the dimensions of structures are scaled down to the micro‐ and nano‐domains, the mechanical behavior becomes size dependent and thus, the classical elasticity solutions cannot be expected to hold. In particular, recent experimental investigations of fatigue strength of metals show pronounced strengthening due to the influences of both grain size and small geometrical dimensions. This paper aims to provide a simple, yet rigorous analytical model in order to address the aforementioned size effects.

The present study employs a framework based on the type II, strain gradient elasticity theory by Mindlin, embedded into a thermodynamics‐based formulation which considers both mechanical behavior parameters and material lengths, as internal variables, in order to model metal fatigue.

A thermodynamics‐based, second gradient elasto‐plastic formulation with an explicit material length, which captures the size effects in fatigue of small‐scale metal components, has been established. From a physical viewpoint, the evolution of the internal length in the constitutive equations with the evolution of the intrinsic wavelength (e.g. persistent slip bands spacing) can be identified signifying the splitting of the grains into sub‐regions and consequently, the softening of the material.

The major novelty of the proposed modeling is that the internal characteristic length considered is not a fixed parameter, but evolves with the plastic effective strain amplitude obtained from cyclic loading.

An experimental investigation for developing structure-property correlations of hot-rolled E410 steels with different carbon contents, i.e. 0.04wt.%C and 0.17wt.%C metal active gas (MAG) and cold metal transfer (CMT)-MAG weldments was undertaken.

Mechanical properties and microstructure of MAG and CMT-MAG weldments of two E410 steels with varying content of carbon were compared using standardized mechanical testing procedures, and conventional microscopy.

0.04wt.%C steel had strained ferritic and cementite sub-structures in blocky shape and large dislocation density, while 0.17wt.%C steel consisted of pearlite and polygonal ductile ferrite. This effected yield strength (YS), and microhardness being larger in 0.04wt.%C steel, %elongation being larger in 0.17wt.%C steel. Weldments of both E410 steels obtained with CMT-MAG performed better than MAG in terms of YS, ultimate tensile strength (UTS), %elongation, and toughness. It was due to low heat input of CMT-MAG that resulted in refinement of weld metal, and subzones of heat affected zone (HAZ).

A substantial improvement in YS (∼9%), %elongation (∼38%), and room temperature impact toughness (∼29%) of 0.04wt.%C E410 steel is achieved with CMT-MAG over MAG welding. Almost ∼10, ∼12.5, and ∼16% increment in YS, %elongation, and toughness of 0.17wt.%C E410 steel is observed with CMT-MAG. Relatively low heat input of CMT-MAG leads to development of fine Widmanstätten and acicular ferrite in weld metal and microstructural refinement in HAZ subzones with nearly similar characteristics of base metal.

Recently nanoparticles reinforced lead free solders are vastly developed in electronics packaging industry. Studies and investigations have been conducted to learn and investigate the types, properties, method, availability and importance of nanoparticles in this field.

Mechanical properties, melting temperature and microstructural conditions are taken into major considerations in any of the preparation on nanoparticles and being reviewed in this paper. Segregation of the types of nanoparticles being added together with their properties is summarized in this paper. High temperature reliability is crucial in providing a good viable solder and hence addition of nanoparticles have been seen to give a positive outcome in this particular property.

This paper reviews on the beneficial of the various nanoparticles addition in the solder. Briefed explanations and the factors are revealed in this review.

This paper reviews on the beneficial of the various nanoparticles addition in the solder.

The purpose of this paper is to investigate the use of nanoindentation with a Berkovich indenter as a method of extracting equivalent stress‐strain curves for the base metal and the welded zone of a friction stir welded aluminum alloy.

Friction stir welding is a solid‐state joining process, which emerged as an alternative technique to be used in high strength alloys that were difficult to join with conventional joining techniques. This technique has a significant effect on the local microstructure and residual stresses combined with deformation. Nano‐ and micro‐indentation are the most commonly used techniques to obtain local mechanical properties of engineering materials. In order to test the reliability of nanoindentation technique and to connect nanoscale with macroscale, the indentation hardness‐depth relation established by Nix and Gao was applied on the experimental values.

The predictions of this model were found to be in good agreement with classical hardness measurements on AA 6082‐T6 aluminum alloy. Also, finite element method provides a numerical tool to calculate complex nanoindentation problems and in correlation with gradients theories forms a well‐seried tool in order to take into account size effects.

By studying this alloy, the paper reviews fundamental principles such as stress‐strain distribution, size effects rise during nanoindentation and the applicability of finite element method, in order to take into account these issues.

Continuum‐atomistic modeling denotes a mixed approach combining the usual framework of continuum mechanics with atomistic features like e.g. interaction potentials. Thereby, the kinematics are typically characterized by the so called Cauchy‐Born rule representing atomic distance vectors in the spatial configuration as an affine mapping of the atomic distance vectors in the material configuration in terms of the local deformation gradient. The application of the Cauchy‐Born rule requires sufficiently homogeneous deformations of the underlying crystal. The model is no more valid if the deformation becomes inhomogeneous. By virtue of the Cauchy‐Born hypothesis, a localization criterion has been derived in terms of the loss of infinitesimal rank‐1 convexity of the strain energy density. According to this criterion, a numerical yield condition has been computed for two different interatomic energy functions. Therewith, the range of the Cauchy‐Born rule validity has been defined, since the strain energy density remains quasiconvex only within the computed yield surface. To provide a possibility to continue the simulation of material response after the loss of quasiconvexity, a relaxation procedure proposed by Tadmor et al. [1] leading necessarily to the development of microstructures has been used. Alternatively to the above mentioned criterion, a stability criterion has been applied to detect the critical deformation. For the study in the postcritical region, the path‐change procedure proposed by Wagner and Wriggers [2] has been adapted for the continuum‐atomistics and modified.

The purpose of this paper is to investigate the effect of the soft annealing time on the microstructure and hydrogen embrittlement (HE) of Fe-0.22C-11.54Mn-2.05Al steels.

Steels A and B with different morphologies were prepared by cold rolling after warm rolling, long/short softening annealing and finally annealing at 700 °C for 30 min. Uncharged and charged samples were subjected to tensile, and HE behavior was studied by electron backscattered diffraction, scanning electron microscopy and X-ray diffraction.

The two samples exhibited similar tensile strengths. The homogeneous equiaxed microstructure of steel B was found to be more conducive to relieve its HE sensitivity. Steel A exhibited bimodal-grained microstructures – blocky and lath. The formation of crack in the blocky grains of steel A resulted in a significant reduction in its plasticity and tensile strength.

The high HE susceptibility of steel A is mainly connected with the inhomogeneity of martensite transformation.