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Mg-1.0Al-1.0Ca-0.4Mn (AXM1104, wt.%) low alloy was extruded at 200 °C with an extrusion ratio of 25 and different ram speeds from 1.0 to 7.0 mm/s. The influence of extrusion rate on microstructure and mechanical properties of the AXM1104 alloy was systematically studied. With the increasing of extrusion rate, the mean dynamically recrystallized (DRXed) grain size of the low alloy and average particles diameter of precipitate second phases were increased, while the degree of grain boundary segregation and the intensity of the basal fiber texture were decreased. With the rising of extrusion rate from 1.0 to 7.0 mm/s, the tensile yield strength (TYS) of the as-extruded AXM1104 alloy was decreased from 445 MPa to 249 MPa, while the elongation to failure (EL) was increased from 5.0% to 17.6%. The TYS, ultimate tensile strength (UTS) and EL of the AXM1104 alloy extruded at the ram speed of 1.5 mm/s was 412 MPa, 419 MPa and 12.0%, respectively, exhibiting comprehensive tensile mechanical properties with ultra-high strength and excellent plasticity. The ultra-high TYS of 412 MPa was mainly due to the strengthening from ultra-fine DRXed grains with segregation of solute atoms at grain boundaries. The strain hardening rate is increase slightly with increasing extrusion speed, which may be ascribed to the increasing mean DRXed grain size with rising extrusion speed. The higher strain hardening rate contributes to the higher EL of these AXM1104 samples extruded at higher ram speed.

The answer of the thin, infinite, central cracked plate, subjected to in-plane loading, is investigated. The plate is made from the ductile metallic material. The two pairs of the concentrate, compressible forces, F, act on the crack surface in the direction perpendicular to it, i.e. in the direction parallel to the axis, y, which is, also, the axis of symmetry. The other edges of the plate, at infinity, are free of loading. The forces, F, open the crack and they are monotonously increased. As, it is well known, if the response of the plate material on the external loading is pure elastic, the stress singularity at the crack tip will be appeared. But, in the case of elastic-plastic response of a plate material there will be no stress singularity at the crack tip, i.e. the normal stress, will assume the ultimate value. The occurrences within the cohesive zones around the crack tips are rather complex and we will try to contribute in the mathematical description of those phenomena. The certain parameters of EPFM, such as, the stress intensity coefficient and the magnitude of cohesive zone, are investigated. An isotropic and non-linear strain hardening of a plate material is assumed. Non-linear strain hardening at uniaxial state of stress is described by the Ramberg-Osgood´s equation. The investigations were carried out for the several different values of the strain hardening exponent n which is changed among the discrete values n = 2, 3, 4, 5, 7, 10, 15, 25, 50 and 1000. One well- known cohesive model (Dugdale´s model) was applied in the crack tip plasticity investigating. Also, it was assumed that the cohesive stresses within the plastic zone are changed according to non- linear law. The stress intensity coefficient from the cohesive stresses is calculated by integrating, using the Green functions method. In the frame of applied cohesive model, the all mathematical expressions were derived fully exact, analytically. Also, the new algorithm was established which enables direct calculation the plastic zone magnitude depended on the magnitude of external loads. The all obtained results are presented in the form of the diagrams. The contemporary mathematical tools, like the software package Wolfram Mathematica, were used. The solutions for the stress intensity coefficient and the magnitude of plastic zone are presented through the special, Gamma and the Hypergeometric functions. References [1] Pustaić, D. and Lovrenić-Jugović, M., Procedia Structural Integrity, vol. 23, 2019, 27- 32. [2] Pustaić, D. and Lovrenić-Jugović, M., Proc. of the 9th Int. Congress of Croatian Society of Mechanics, ISSN 2623-6133, Marović, P., Krstulović- Opara, L. and Galić, M., eds., Split, Croatia, 2018. [3] Wolfram Mathematica 7.0, Champaign II, 2017, http://www.wolfram.com/products/mathematica/. [4] Guo, W., Engineering Fracture Mechanics, vol. 51 (1), 1995, 51-71. [5] Neimitz, A., Engineering Fracture Mechanics, vol. 71 (11), 2004, 1585-1600. [6] Pustaić, D. and Lovrenić, M., Proc. of the 5th Int. Congress of Croatian Society of Mechanics, Matejiček, F. et al., eds. Trogir, Croatia, 2006. [7] Pustaić, D. and Štok, B., Proc. of the 12th European Conference on Fracture, Brown, M. W., de los Rios, E. R. and Miller, K. J., Sheffield, 1998, 889-894.

The heterogeneous magnesium (Mg) matrix nanocomposite with dispersed soft phase exhibits high strength and toughness. Herein, the deformation behavior and failure process were investigated to reveal the unique mechanical behavior of the heterogeneous microstructure under compression. The extensive plastic deformation is accompanied by the flattening and tilting of the soft phase, inhibiting strain localization and leading to strain hardening. Moreover, a stable crack multiplication process is activated, which endows high damage tolerance to the heterogeneous Mg matrix nanocomposites. The final failure of the composite is caused by crack coalescence in the shear plane along a tortuous path. The presence of dispersed soft phases within the hard matrix induces a noticeable change in mechanical response. Especially, the malleability of the heterogeneous Mg matrix nanocomposite is two and ten times higher than that of pure Mg and the homogeneous Mg matrix nanocomposite, respectively. The current study provides a novel strategy to break the trade-off between strength and toughness in metal matrix nanocomposites.

The emphasis of this exploration was to examine the workability and work hardening performance of Mg (Magnesium) specimen and Mg-B4C composites created via the powder metallurgy technique. The pure Mg and Mg-B4C composites are made with distinct weight percentages (Mg-5% B4C, Mg-10% B4C, and Mg-15% B4C) at the unit aspect ratio. The powders and composites characterization are executed by SEM (Scanning Electron Microscope), EDS (Energy Dispersive Spectrum) with an elemental map, and XRD (X-ray Diffraction) examination. It displays that, the B4C particles were dispersed consistently with the Mg matrix. The workability and work hardening examination was conducted in triaxial stress conditions using the cold deformation process. The consequence of workability stress exponent factor (βσ), distinct stress proportion factors (σm/σeff and σθ/σeff), instantaneous work hardening exponent (ni), work hardening exponent (n), coefficient of strength (k) and instantaneous coefficient of strength (ki) are recognized. The outcome displays that Mg-15% B4C specimen has greater workability and work hardening parameter, initial relative density, and triaxial stresses compared with the Mg specimen and Mg-(5–10%) B4C composites.

High- and medium-entropy alloys (HEAs and MEAs) possess high solid-solution strength. Numerous investigations have been conducted on its impact on yield strength, however, there are limited reports regarding the relation between solid-solution strengthening and strain-hardening rate. In addition, no attempt has been made to account for the dislocation-mediated plasticity; most works focused on twinning- or transformation-induced plasticity (TWIP or TRIP). In this work we reveal the role of solid-solution strengthening on the strain-hardening rate via systematically investigating evolutions of deformation structures by controlling the Cr/V ratio in prototypical V1-xCrxCoNi alloys. Comparing the TWIP of CrCoNi with the dislocation slip of V0.4Cr0.6CoNi, the hardening rate of CrCoNi was superior to slip-band refinements of V0.4Cr0.6CoNi due to the dynamic Hall-Petch effect. However, as V content increased further to V0.7Cr0.3CoNi and VCoNi, their rate of slip-band refinement in V0.7Cr0.3CoNi and VCoNi with high solid-solution strength surpassed that of CrCoNi. Although it is generally accepted in conventional alloys that deformation twinning results in a higher strain-hardening rate than dislocation-mediated plasticity, we observed that the latter can be predominant in the former under an activated huge solid-solution strengthening effect. The high solid-solution strength lowered the cross-slip activation and consequently retarded the dislocation rearrangement rate, i.e., the dynamic recovery. This delay in the hardening rate decrease, therefore, increased the strain-hardening rate, results in an overall higher strain-hardening rate of V-rich alloys.

The grain orientation control via twinning activity on deformation features is of great significance to offer a key insight into understanding the deformation mechanism of Mg alloy sheets. The {10–12} twinning were performed by pre-strain paths, i.e., tension (6%) and compression (5%) perpendicular to the c-axis along extrusion direction (ED), to investigate the microstructural evolution and mechanical properties of AZ31 Mg alloy sheets. The distinction in the texture evolution and strain hardening behavior was illustrated in connection with the pre-strain paths for the activities of twinning and slip. The result shows that the activation of the deformation mode was closely bound up with the grain orientation and the additional applied load direction. The {10–12} twin-texture components with c-axis//ED were generated by pre-compression, which can provide an appropriate alternative to accommodate the thin sheet thickness strain and enhance the room temperature formability of Mg alloy sheet.

We use a three-dimensional (3D) microvascular platform to measure the elasticity and membrane permeability of the endothelial cell layer. The microfluidic platform is connected with a pneumatic pressure controller to apply hydrostatic pressure. The deformation is measured by tracking the mean vessel diameter under varying pressures up to 300 Pa. We obtain a value for the Young's modulus of the cell layer in low strain where a linear elastic response is observed and use a hyperelastic model that describes the strain hardening observed at larger strains (pressure). A fluorescent dye is used to track the flow through the cell layer to determine the membrane flow resistance as a function of applied pressure. Finally, we track the 3D positions of cell nuclei while the vessel is pressurized to observe local deformation and correlate inter-cell deformation with the local structure of the cell layer. This approach is able to probe the mechanical properties of blood vessels in vitro and provides a methodology for investigating microvascular related diseases.

This work deals with studying staging and macroscopic strain localization in austenitic stainless steel 12Kh18N9T within a temperature range of 143 K < T < 420 K. The visualization and evolution of macroscopic localized plastic deformation bands at different stages of work hardening were carried out by the method of the double-exposure speckle photography (DESP), which allows registering displacement fields with a high accuracy by tracing changes on the surface of the material under study and then comparing the specklograms recorded during uniaxial tension. The shape of the tensile curves σ(ε) undergoes a significant change with a decreasing temperature due to the γ-α'-phase transformation induced by plastic deformation. The processing of the deformation curves of the steel samples made it possible to distinguish the following stages of strain hardening, i.e. the stage of linear hardening and jerky flow stage. A comparative analysis of the design diagrams (with the introduction of additional parameters of the Ludwigson equation) and experimental diagrams of tension of steel 12Kh18N9T for different temperatures is carried out. The analysis of local strains distributions showed that at the stage of linear work hardening, a mobile system of plastic strain localization centers is observed. The temperature dependence of the parameters of plastic deformation localization at the stages of linear work hardening has been established. Unlike the linear hardening, the jerky flow possesses the propagation of single plastic strain fronts that occur one after another through the sample due to the γ-α' phase transition and the Portevin-Le Chatelier effect. It was found that at the jerky flow stage, which is the final stage before the destruction of the sample, the centers of deformation localization do not merge, leading to the neck formation.

The numerical simulations of the deformation and fracture in an iron boride coating – steel substrate composition are presented. The dynamic boundary-value problem is solved numerically by the finite-difference method. A complex geometry of the borided coating – steel substrate interface is taken into account explicitly. To simulate the mechanical behavior of the steel substrate, use is made of an isotropic strain hardening model including a relation for shear band propagation. Local regions of bulk tension are shown to arise near the interface even under simple uniaxial compression of the composition and in so doing they determine the mesoscale mechanisms of fracture. The interrelation between plastic deformation in the steel substrate and cracking of the borided coating is studied. Stages of shear band front propagation attributable to the interface complex geometry have been revealed. The coating cracking pattern, location of the fracture onset regions and the total crack length are found to depend on the front velocity in the steel substrate.

Although the shear behaviors of silt–structure interfaces are critical in engineering practice, they have not been extensively investigated systematically. In this study, the influence of the silt water content and interface roughness on the shear behaviors of silt–cement mortar interfaces is investigated. Forty–eight silt–cement mortar structure interface tests and 18 silt direct shear tests were carried out. The results indicated that as the water content of the silt gradually increased to saturation, the interface shear stress–displacement curves changed from strain softening to strain hardening, and the interface shear strength decreased significantly. The shear strength of the rough interface was found to be significantly greater than of the silt, and the shear strength of the smooth interface was found to be lower than that of the silt. The interface shear strength gradually increased with the surface roughness, but the increase tended to be gentle. A large shear deformation was observed, and this increased with the decrease in soil water content and the increase (up to a point) in interface roughness. A model of the interface shear strength between unsaturated soil and structures considering the influence of water content and interface roughness was established and verified.

The demand for magnesium (Mg) alloy with high elongation, certain strength and good degradation rate used in oil and gas exploitation filed is increasing. Based on Mg-2Gd alloy, effect of copper (Cu) addition (0.25, 0.5 and 0.75 wt.%) on microstructure, mechanical properties and degradation rate were investigated. It showed that more Mg2Cu second phases were precipitated and the grain size was refined with increasing Cu content, accompanied with texture changing from 11 2 ¯ 1 > //ED to 01 1 ¯ 0 > //ED. As a result, hardness, tensile strength, compressive strength and degradation rate were enhanced while the strain hardening rate and elongation decreased. Nevertheless, the elongation was still up to at least 20%. Overall, the comprehensive mechanical properties and degradation rate of Mg-2Gd alloy can be effectively coordinated by Cu addition.

Electrically assisted (EA) microforming has pervasive benefits for the fabrication of high-performance microproducts. In this research, the coupled effect between the microstructural size effect and pulsed current on the flow characteristics of 304 stainless steel sheets along thickness direction was explored by using EA micro-compression tests. The results revealed that the strain hardening rate and the deformation stress of 304 stainless steel decreases during the EA deformation, especially when the current density exceeds 57.16 A/mm2. Besides, the effect of grain size on the micro-scaled compression is gradually weakened with the augment of current density and plastic strain. The electron backscatter diffraction (EBSD) results showed in the perspective of microstructure that the decrease of flow stress and strain hardening rate with the rise of pulsed current density is related to the reduction of dislocation density and texture strength due to the dynamic recrystallization during EA deformation. The pulsed current suppresses the grain refinement of fine-grained material and promotes that of coarse-grained material, and the recrystallization rate of EA deformation increases with the decrease of initial grain size. In addition, the recrystallization texture induced by the pulsed current can promote grain deflection and weakens the effect of twins in coarse-grained material. That can explain the reason for the weakening of the grain size effect. The findings in the research have important guiding significance for understanding the coupled mechanism of electroplastic and grain size effect on the flow characteristics of difficult-to-deform material, and further promoting the application of EA micro-rolling of high-strength materials.

Phase transformation changes numerous properties of materials. Ti–Pt alloys have received much interest because of high martensitic transformation temperature. However, the intrinsic brittleness of these intermetallic compounds with low crystal symmetry and complicated phase structure limit their applications, especially when composition deviates from stoichiometry ratio. By performing in situ heating high-resolution scanning transmission electron microscopy experiment and micro-mechanical testing on Ti-35 at% Pt that contained majorly Ti3Pt and αTiPt phases, it was found that precipitating herringbone twinned αTiPt islands within Ti3Pt could occur upon heating, significantly refining mixed-phase structure. The refinement of multi-intermetallic mixed-phase structure endowed brittle material with remarkable capacity for plastic deformation and strain hardening. The plastic deformation mechanisms include phase transformation upon yielding and dislocation slips during hardening, which rarely occurs in intermetallic compounds with low symmetry. The strong interaction between different deformation modes even caused nano-crystallization along slip bands. The results demonstrate that brittle-to-ductile transition in intermetallic compounds can be achieved by tuning mixed-phase structure through phase transformations.

The deformation behavior in the isothermal compression of Ti-46.5Al–2Nb–2Cr (at. %) including flow stress and microstructure evolution at the deformation temperatures ranging from 1373 to 1533 K and strain rates from 0.001 to 1 s−1 were investigated. The phenomenological-based model was established by describing the variation of the strain hardening exponent with the increasing of strain. The strain rate sensitivity exponent ranging from 0.065 to 0.449 indicated the transition of deformation mechanism from dislocation creep to grain boundary sliding, and the model by considering the effect of the processing parameters on the strain rate sensitivity was presented. The effect of the processing parameters on the apparent activation energy for deformation was analyzed. Furthermore, the novel constitutive model coupling with the strain hardening exponent and strain rate sensitivity exponent in the deformation was put forward and applied to predict the deformation behavior of Ti-46.5Al–2Nb–2Cr.

In this paper, high-strength ultrafine-grained (UFG) pure aluminum (Al) was successfully achieved via a two-step processing route including room-temperature ECAP process for continuously 16 passes and post liquid nitrogen cryo-rolling for 50% reduction. The two-step processing route was observed to produce ultrafine grains with an average grain size of 0.98 μm and has obvious advantages for the preparation of high-strength pure Al in terms of the strength-ductility synergistic effect, which endows the pure Al excellent UTS value of 180 MPa, good Ef of 17.7% and a very high increase ratio (about 84%) of strength. The high strength was mainly attributed to the outstanding fine-grain strengthening provided by the combination of large-pass ECAP and cryo-rolling. In addition, the better uniform elongation of ECAP-rolled pure Al than ECAPed one was primarily dictated by the enhanced strain hardening capacity and the elongated grain shape.

The Gleeble-3800 thermal simulator is used to perform isothermal and constant strain rate compression tests on SP700 titanium alloy under the conditions of deformation temperature of 700–950 °C and strain rate of 0.001–1 s−1. The processing map technology can be obtained based on dynamic material model, through this technology, its thermal deformation behavior can be studied and the appropriate processing parameter range can be optimized by combining the changes in the strain rate sensitivity exponent m, strain hardening exponent n and deformation activation energy Q. The results show that the flow stress of SP700 titanium alloy is sensitive to deformation temperature and strain rate. When the strain is 0.9, the strain rate sensitivity exponent m is greater than 0.5 when the deformation temperature is 800 °C and the strain rate is 0.001 s−1 and 1 s−1. Under this condition, the SP700 titanium alloy may have superplastic deformed. In addition, the analysis shows that when the deformation temperature is 775–825 °C, the strain rate is 0.3–1 s−1 and 0.001–0.002 s−1, this condition is the best processing parameter range of SP700 titanium alloy.

The advent of additive manufacturing (AM) offers the possibility of creating high-performance metallic materials with unique microstructure. Ultrafine dislocation cell structure in AM metals is believed to play a critical role in strengthening and hardening. However, its behavior is typically considered to be associated with alloying elements. Here we report that dislocations in AM metallic materials are self-stabilized even without the alloying effect. The heating–cooling cycles that are inherent to laser power-bed-fusion processes can stabilize dislocation network in situ by forming Lomer locks and a complex dislocation network. This unique dislocation assembly blocks and accumulates dislocations for strengthening and steady strain hardening, thereby rendering better material strength but several folds improvements in uniform tensile elongation compared to those made by traditional methods. The principles of dislocation manipulation and self-assembly are applicable to metals/alloys obtained by conventional routes in turn, through a simple post-cyclic deformation processing that mimics the micromechanics of AM. This work demonstrates the capability of AM to locally tune dislocation structures and achieve high-performance metallic materials.

Interstitial-free steel is very soft and ductile, with a fully ferritic microstructure at room temperature. In order to address this issue in the present work, the cold-rolling increases tensile strength vividly by strain hardening. The heat-treatment thereafter optimizes strength-ductility, with an excellent combination, through fine recrystallized grains. The warm-rolled sample provides relatively an inferior property by partial recrystallization of the sample. Irrespective of unannihilated dislocations, both the samples after the recrystallization treatment in the austenitic domain at 925 °C, were water quenched in a laboratory scale to explore phase transformations additionally in the system. The microstructural characterization reveals that the nucleation of massive ferrite under rapid cooling requires austenite conditioning, similar to martensite in the alloy, constrained by strained lattice. The outcome fundamentally argues against the notion that the accumulation of crystal defects/dislocations promotes an extra driving force for a reconstructive phase transformation leading to massive ferrite.

We report the mechanical and microstructural characteristics of a medium-entropy alloy, Co17.5Cr12.5Fe55Ni10Mo5 (atomic percent, at%) at cryogenic temperatures, down to a record low temperature of 0.5 K. The alloy exhibits excellent strength and ductility combined with a high strain-hardening rate in the entire temperature range investigated. Its property profile, including the yield strength, ultimate tensile strength, strain hardening capability, and absorbed mechanical energy, is better than those of most alloys and HEAs used in cryogenics. Within the interval of extremely low temperatures considered (0.5–4.2 K), the alloy exhibits several unusual features, including anomalies of the temperature dependence of the yield strength and tensile ductility, discontinuous plastic deformation (DPF), and a change in the propensity for the deformation-induced martensitic transformation. While the occurrence of these effects in the same temperature interval may be fortuitous, we hypothesize that they are interrelated and provide a tentative explanation of the observed phenomena on this basis.

The split Hopkinson pressure bar and universal testing machine are used to study the dynamic response and failure behavior of U71Mn using a hat-shaped specimen under the compression-shear stress state. The shear stress–strain curves are presented at the shear strain rates ranging from 0.001 to 19,200 s−1 and temperatures ranging from 25 to 600 °C. It is observed that the effects of strain rate hardening, strain hardening, and thermal softening are closely related to the changes of the shear stress–strain curves. The coupling effects are very significant in the process of deformation failure. The fracture morphology and longitudinal section microstructures of U71Mn are investigated by scanning electron microscope. According to the results, the shear strain rates and temperatures greatly influence the failure mechanisms of the material. Furthermore, the increase in temperature promotes the occurrence of dynamic recrystallization and reduces the tendency of the pearlite flowing toward the center of the shear zone. Based on the quasi-static tensile tests and finite element analysis, the Johnson–Cook damage model parameters are fitted and applied to the finite element analysis of the hat-shaped specimen.

The microstructural evolution, deformation modes, and fracture mechanisms of zirconium plate produced using ultrasonic additive manufacturing (UAM) are presented. In addition to conventional tensile testing techniques, digital image correlation captured highly variable strain accumulation in specimens loaded perpendicular or parallel to the build height (Z). When tested in parallel to Z, delamination at prior foil/foil interfaces creates strain localization noticeable in strain rate maps, whereas specimens loaded perpendicular to Z illustrate conventional strain hardening until necking accelerates delamination. Although bond strengths are statistically and spatially variable, in situ electron backscattering diffraction tests illustrate the ability for grains near interfaces to accommodate strain with twinning and slip modes consistent with conventionally produced zirconium alloys. Finally, mixtures of ductile and delamination-induced fracture highlight the interface-driven failure modes of UAM zirconium plate in the as-built condition. Graphic abstract

Inconel 718 is widely used in many applications specifically in the aerospace and nuclear industry due to its superior properties in strength, hot hardness, and thermal and corrosion resistance. However, it is classified as difficult-to-cut material due to its extreme hardness that led to high cutting forces and temperature which further worsened by its strain hardening effect. Thus, it is crucial to analyze the different types of wear mechanisms and failure modes, to analyze causes, and also to understand how cutting parameters affect the wear mechanisms and failure modes. The study is conducted with PVD TiAlN-NbN coated inserts with varying cutting speeds (40, 60, and 80 m/min) and varying feed/tooth (0.7, 0.1, and 0.13 mm/tooth) under the wet condition of face milling. The flank wear progression and length of cut were measured and recorded to study the tool life against length of cut. The tool wear and failure modes of inserts were observed under the optical microscope and SEM/EDX. Results showed that cutting speed has a major effect on the tool failure as compared to feed/tooth. At low speed, the dominant tool failures were macro-chipping due to the severe BUE (built-up edge)/BUL (built-up layers) formation. At higher speeds, the dominant tool failures were flaking and notching which led to the sudden tool breakage. At low feed/tooth, the dominant failures were flaking and macro-chipping, but notching and tool breakage became dominant at higher feed/tooth. Moreover, it is found that the main wear mechanisms which contributed to the tool failures were adhesion, abrasion, thermal and mechanical cracks, diffusion and oxidation wear.

Effects of Al addition to a Mg–Sn–Ca ternary alloy on its microstructure and tensile properties after extrusion were studied via extrusion of Mg-1.0Sn-0.5Ca-xAl (x ​= ​0, 0.8, 2.4 ​wt%) sheets and analysis of the extruded materials. The results showed that Al addition not only refined the grain size (from 9.8 ​± ​0.7 ​μm to 8.3 ​± ​0.4 ​μm and 7.6 ​± ​0.5 ​μm) but also accelerated the generation of more second phase (from 0.98 to 1.72 and 4.32%). Except for the CaMgSn and Mg2Ca in Mg-1.0Sn-0.5Ca alloy, new phase (Mg, Al)2Ca appeared after Al addition. The addition of Al into Mg–Sn–Ca alloy induced the textural variation from an initially ED-split double-peaked texture to a weakened texture, i.e., divergent elliptical texture, due to the effect of particle stimulated nucleation. This eventually contributed to the improvement of mechanical anisotropy as well as the higher Hc value and n-value. For the strain hardening behavior when tension along the TD, the prolonged stage Ⅱ of Al-modified alloys was closely connected with the additional TD textural components, accelerating the activation of more basal slip. The decreased θⅢ0 in stage Ⅲ of Al-modified alloys is beneficial to the grain refinement and the emergence of more second phase.

Aluminum foil undergoes severe plastic deformation and multiple heat treatments during processing, and the texture characteristics become very identifiable. In this research, textured AA8021 aluminum foil was obtained by adjusting the fabrication process. The anisotropic behavior of aluminum foil was studied by tensile testing. The surface morphology and texture evolution of the aluminum foil were studied before and after tensile testing by means of digital microscopy, optical profilometry and electron backscattered diffraction. The experimental results showed that compared with the samples tested at 0° and 90° to the rolling direction, the samples tested at 45° to the rolling direction exhibited lower yield strengths and flow stresses due to the “soft orientation” of most grains. Additionally, when the aluminum foil was tensile tested at 45° to the rolling direction, the shear bands on the surface of the aluminum foil were long, dense, bent and crossed. The rotation of cube grains caused the aluminum foil matrix to undergo significant geometric hardening, increasing the strain hardening index n. Additionally, the rolling texture improved the anti-thinning ability of the aluminum foil at 45° to the rolling direction, significantly increasing the ultimate strain reached in the 45° direction. These research results provide important theoretical guidance for improving the drawability of aluminum foil box-shaped parts by adjusting the microtexture under industrial conditions.

This study investigates a novel forming design, that is, intercritical rolling (IR) + low-temperature rolling (LTR) + short-time intercritical annealing (STIA) + one-step stamping (OSS), to decrease or eliminate the yield point elongation (YPE) in a medium-Mn alloy. Results show that the novel forming design leads to ultra-fine microstructure and excellent mechanical properties in the stamped parts. The dislocation density or austenite mechanical stability may be the underlying reasons for the decreased YPE in medium-Mn steels. This novel forming design can increase the work hardening exponent of experimental samples by increasing the dislocation density in ferrite or decreasing austenite mechanical stability, resulting in a continuous yielding feature in stamped parts.

The current work explores the strain hardening and stretches formability behaviour of the developed Triple Phase (TP) steel. Double quenched TP steel strips posse three distinguished stages of strain hardening on tensile forming. 1st stage represents the highest n-value reflecting resistance to homogeneous deformation, where steel can be safely stretched. 2nd and 3rd stage reveals lower n-values, where localized thinning exist. On Erichsen testing, the relationship between punch forming force and punch stroke exhibits two forming regions. The 1st region is delineated by a straight line showing an ultra-high strain-hardening rate, which represents a reversible elastic stretch forming. The 2nd forming region continues to a higher Erichsen punch stroke than that of the 1st region and presents the permanent plastic stretch forming behaviour. It is found that bainite and martensite clusters created, by double quenching, in TP-steel exaggerated the elastic stretch forming limit 10 times higher than the as-hot rolled condition. 7 min. holding time of strips in the salt bath is considered the most effective for the creation of a useful volume fraction of the bainite phase. However, 21 min. holding time in salt bath grows martensite laths through the bainite aggregates, affecting negatively on stretch formability.

The welding of dissimilar armor-grade steels is always challenging due to their carbon equivalent (CE) differences. In this investigation, dissimilar armor-grade steels (rolled homogenous armor (RHA) steels and ultra-high hard armor (UHA) steel) are welded using three electrodes, namely low hydrogen ferritic (LHF), austenitic stainless steel (ASS), and duplex stainless steel (DSS) by shielded metal arc welding (SMAW) process. All the three joints were tested against the 7.62 × 54 mm armor-piercing (AP) projectile. The projectile was wholly stopped at the Weld Metal (WM). Three modes of failures were observed in WM (1) wear debris (WD), (2) wear debris + continuous cracks (WDCC), and (3) fine wear debris + microcracks (FWDMC). The joint fabricated using ASS electrode with the level of failure of WDCC performs better than other joints with the lowest area density of 70 kg/m2 due to the high energy absorption capability of the austenite phase and higher strain hardening properties. At the interface, the martensitic band (MB) increases the hardness and has a vital role in determining ballistic resistance. The impact toughness and ductility of the weld metal play a significant role in deciding the ballistic performance more than hardness and strength properties.

The microstructures and mechanical properties of Ti-6Al-4V fabricated using laser metal deposition (LMD) and electron beam melting (EBM) were investigated and compared. The hardness, strength and work hardening exponent (n) of the LMD samples are superior to that of EBM samples. The EBM samples are more ductile, exhibit resistance to rapid plastic strain localization and have uniform hardness throughout the build. A detailed microstructural characterization was conducted for both alloys before and after the tensile tests. The differences in mechanical behavior of the two samples originate from their distinct dislocation densities within α and the relative proportions of Widmanstatten and colony type arrangements of the α+β laths, which in turn are an outcome of the distinct cooling profiles in the two additive manufacturing methods. On the basis of these results, strategies to improve the mechanical properties of both alloys are discussed.

An investigation is conducted into the behaviour of bolted endplate connections between high-strength steel tubular members at elevated temperatures. Experiments are described where assemblies comprising Grade S460 steel square hollow sections connected via bolted endplates are heated to a target temperature between 150°C and 750°C using ceramic heating pads. The assembly, which is inclined at 45° to the horizontal, is then loaded vertically, thus generating combined bending and axial thrust in the members. The in-plane vertical deflection, the applied load and temperatures at various points were measured. Results for the ultimate loads, equilibrium paths and the observed failure modes are discussed along with the influence of temperature on these features. A complementary nonlinear finite element analysis of the experimental assemblies is also described. Material models incorporating temperature-dependent strengths, stiffnesses and strain hardening relationships available from the literature are employed, with temperature fields calibrated using steel temperatures recorded during the experiments applied to the models. It is shown that good agreement exists between the ultimate loads, equilibrium paths and failure modes predicted by the numerical models and those observed in the experiments, thus validating the modelling approach. It is found that, at lower temperatures, buckling of the endplate was the governing mode of failure. With increasing temperature, the mode of failure transitions to flexure in the beam and column stubs, thus suggesting that a relative degree of fixity is offered by the connections at the higher temperatures.

The effects of aging treatments on the tensile properties and compressive behavior of a thin-walled 6005 aluminum alloy tube were studied. Samples after three natural aging (NA) conditions were subsequently aged at 180 °C for 0.5–12.0 h artificial aging (AA). Tensile and compressive tests were performed after AA. The results show that for samples with the same NA, the longer the AA time is, the higher the strengths alloy owns, and at the same time the material shows a much lower elongation and faster process from plastic deformation to fracture. However, with NA prolonging, the alloy exhibits much better plastic deformation ability after AA, though its strength is decreased. The major cause of strength and plasticity variation induced by changing NA time is that the size of the main strengthening β″ precipitates is larger and the density is lower. This character is evaluated by the strain hardening exponent n. Compressive results show that the optimum energy absorption characteristics can be acquired at a moderate n (14