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International audience; A simple, first order description of the formation of ε- and α′-martensite in meta-stable austenitic Fe–Mn alloys containing 12–35 wt% Mn was developed. Given the initial volume fractions of ε- and α′-martensite in the non-deformed material, it is possible to calculate the evolution of phase fractions as a function of applied strain. An accurate estimate of the initial amounts of ε- and α′-martensite based solely on the Mn content of the alloy, could not be obtained due to the important role of microstructure features and processing conditions on the martensitic transformations.

Abstract Densely consolidated WC-based hard materials with 5–20 vol% ZrSiO4 was fabricated by spark plasma sintering at 1400 ℃ at a constant heating rate of 70 ℃/min−1. To achieve mechanical alloying of WC-ZrSiO4, planetary ball milling was carried out for 12 h, during which the brittle-brittle components (WC-ZrSiO4) became fragmented and their particles became refined. It was observed that certain, specific, non-isothermal sintering kinetics, such as apparent activation energy, sintering exponents, and densification strain, affected the densification behavior. The evolution of phase structure from powder to compact was found to be related the lattice distortion and micro-strain in the basal planes of WC. By examining the mechanical properties of the samples, it was that the added zircon content leads to enhanced fracture toughness (12.9 MPa m1/2) owing to the presence of WC-ZrSiO4 in the cemented carbide. In fact, the microcrack propagation of the fracture passed through zircon from a transgranular to a ductile component (fcc) where the crack tips could be absorbed. Graphic Abstract

With increasing requirements of continuous arc additive remanufacturing for robots in mold repair, the alloy and slag systems in the traditional flux-cored wire have to be further improved. Especially in order to realize welding automation, the content of slag must be cut down to decrease the time of removing the slag during the deposition. In this paper, Al–Mg and ferrotitanium are used as deoxidizer to make up the side effect caused by lessening the slag. Six kinds of micro-slag gas-shielded flux-cored wires with different content of deoxidizer based on the commercial cored wire RMD535 were developed. The effect of deoxidizer on microstructure and mechanical properties of micro-slag gas-shielded flux-cored wires were studied. The results demonstrated that the microstructure of deposited metal was mainly composed of acicular ferrite and proeutectoid ferrite. With the increase of deoxidizer content, the toughness increases and then decrease, reaching the maximum of 33.45 J and 35.02 J at Ag–Mg alloy and ferrotitanium content of 1.2% and 1.8%. The hardness is constantly increasing. Six kinds of welding wire had different properties, mainly because of the different characteristics of the inclusions in the deposited metal. The spherical inclusion was the result of deoxidation by Al–Mg alloy or ferrotitanium and the diameter in range of 0.4–0.8 μm were effective for acicular ferrite nucleation. However, inclusions predominantly TiOX were more effective than that of Al2O3 in the same size. The present work provided an effective way to improve the impact toughness of deposited metal by the control of deoxidizer content.

Integration of two metallurgically distinct materials (bimetallic) is an inevitable advancement in the automotive and marine field. In this context, this study investigates the fabrication, characterization, and properties of solid–liquid compound cast aluminum alloy AA5052 and ferrous alloy (mild steel and galvanized iron) based bimetallic materials. Microstructural evolution, microhardness, and tensile strength of the developed bimetallic material are investigated. The results show that the formation of cracks at the interface in AA5052/Mild Steel caused the joint failure in the course of preliminary testing. In AA5052/Galvanized Iron, the growth of intermetallics at the oxide-free steel surface results in a shear strength of 19.9 MPa. XRD analysis attests to the presence of brittle intermetallics and Al bond at the interface of AA5052/Galvanized Iron bimetallic material, which in turn confirms the development of a metallurgical.

Friction Stir Welding (FSW) has great potential over fusion welding for joining dissimilar alloys. However, formation of intermetallic compounds (IMCs) Al12Mg17 and Al3Mg2 in FSW of Al/Mg alloys is almost unavoidable and problematic for the research community. Such IMCs in the form of continuous layer provide easy crack propagation path which increases brittleness and reduces the joint strength of the weld. To improve the material flow behavior and reducing brittleness, accurate and precise attempts were taken to join two dissimilar alloys i.e. Al 7075 and Mg AZ31 with the incorporation of cadmium interlayer first time. Tool rotational speed of 1300 rpm and traverse speed of 20 mm/min were maintained throughout the welding process. Various phase formation and their distribution in the nugget zone has been studied in details by using optical microscopy, SEM–EDS and XRD. The supersaturated solid solution (SSSS) of Mg in Al, and a thin layer of Al3Mg2 and small particles (~ 1 µm) of Al12Mg17 have been observed in the stir zone. During processing Cd reacted with Mg and formed CdMg and CdMg3 which have been distributed in the upper-middle portion of Mg region as intercalated lamellar structure. Formation of these compound provided micro-mechanical interlocking. Further, Al material has been found to be deposited into the Mg region in the form of elongated balloon which provided anchoring effect due to mechanical interlocking. The maximum tensile strength achieved is 129 MPa which is higher than the previously reported dissimilar FSW of Al 7xxx series alloy with Mg alloy. Fractographic study of the dissimilar FSW tensile sample was carried out to understand crack propagation path and scope for further improvement in the weld joint strength.

The goal of the present research is to introduce the Tungsten (W) nanoparticles as reinforcement into Al 6063 alloy to produce Al–W nanocomposites by the FSP technique. The vol% of the reinforcement was varied from 3 to 12 with a step of 3, besides the unreinforced Al matrix was considered as 0 vol% for comparison. The role of W nanoparticles in the Al 6063 matrix has been exhaustively investigated using advanced characterization techniques such as XRD analysis to observe the phases, FESEM to detect the distribution of reinforcements with their interparticle spacing and the average grain sizes, TEM analysis to study the strengthening factors, new phase formation at the interface between AA 6063 matrix and W particles, the morphology of the W nanoparticles. The achieved average matrix grains size was 42, 2, and 0.9 μm for 0, 6, and 12 vol% W nanocomposites, respectively. The obtained results disclosed the uniform dispersion of W nanoparticles, without any agglomeration, and with the absence of intermetallic compounds. The hardness and wear resistance of the fabricated nanocomposites were increased incommensurate with the incorporation of heavy metallic W element as reinforcement particle; which was due to the proper dispersion of W nanoparticles, refinement of matrix grains to ultrafine level, generation of dislocations, and clear interface between Al 6063 matrix and W nanoparticles. In a nutshell, AA 6063–12 vol% W nanocomposite has achieved the higher hardness (120 HV), lower wear rate (0.13 mm3/m), and friction coefficient (0.33) than other nanocomposites The goal of the present research is to introduce the Tungsten (W) nanoparticles as reinforcement into Al 6063 alloy to produce Al–W nanocomposites by the FSP technique. The vol% of the reinforcement was varied from 3 to 12 with a step of 3, besides the unreinforced Al matrix was considered as 0 vol% for comparison. The role of W nanoparticles in the Al 6063 matrix has been exhaustively investigated using advanced characterization techniques such as XRD analysis to observe the phases, FESEM to detect the distribution of reinforcements with their interparticle spacing and the average grain sizes, TEM analysis to study the strengthening factors, new phase formation at the interface between AA 6063 matrix and W particles, the morphology of the W nanoparticles. The achieved average matrix grains size was 42, 2, and 0.9 μm for 0, 6, and 12 vol% W nanocomposites, respectively. The obtained results disclosed the uniform dispersion of W nanoparticles, without any agglomeration, and with the absence of intermetallic compounds. The hardness and wear resistance of the fabricated nanocomposites were increased incommensurate with the incorporation of heavy metallic W element as reinforcement particle; which was due to the proper dispersion of W nanoparticles, refinement of matrix grains to ultrafine level, generation of dislocations, and clear interface between Al 6063 matrix and W nanoparticles. In a nutshell, AA 6063–12 vol% W nanocomposite has achieved the higher hardness (120 HV), lower wear rate (0.13 mm3/m), and friction coefficient (0.33) than other nanocomposites.The goal of the present research is to introduce the Tungsten (W) nanoparticles as reinforcement into Al 6063 alloy to produce Al–W nanocomposites by the FSP technique. The vol% of the reinforcement was varied from 3 to 12 with a step of 3, besides the unreinforced Al matrix was considered as 0 vol% for comparison. The role of W nanoparticles in the Al 6063 matrix has been exhaustively investigated using advanced characterization techniques such as XRD analysis to observe the phases, FESEM to detect the distribution of reinforcements with their interparticle spacing and the average grain sizes, TEM analysis to study the strengthening factors, new phase formation at the interface between AA 6063 matrix and W particles, the morphology of the W nanoparticles. The achieved average matrix grains size was 42, 2, and 0.9 μm for 0, 6, and 12 vol% W nanocomposites, respectively. The obtained results disclosed the uniform dispersion of W nanoparticles, without any agglomeration, and with the absence of intermetallic compounds. The hardness and wear resistance of the fabricated nanocomposites were increased incommensurate with the incorporation of heavy metallic W element as reinforcement particle; which was due to the proper dispersion of W nanoparticles, refinement of matrix grains to ultrafine level, generation of dislocations, and clear interface between Al 6063 matrix and W nanoparticles. In a nutshell, AA 6063–12 vol% W nanocomposite has achieved the higher hardness (120 HV), lower wear rate (0.13 mm3/m), and friction coefficient (0.33) than other nanocomposites.

The cyclic deep cryogenic treatment was proposed to improve both the hardness and corrosion resistance of the high strength 7075 aluminum alloy. The effect of different CDCT times on the exfoliation corrosion and intergranular corrosion of the alloys were observed by scanning electron microscope. The corrosion behaviors of the alloys were monitored by electrochemical techniques. The hardness of the alloy was measured by Vickers hardness tester. Furthermore, the microstructures of the alloys were examined by transmission electron microscope. The results show that the corrosion resistance and hardness are strongly affected by the precipitate state. The discontinuous grain boundary precipitates and the wide precipitate free zones will enhance the corrosion resistance. The fine precipitates distributed evenly in the matrix can increase the hardness. After the CDCT, the corrosion resistance is remarkably improved without sacrificing the hardness. The best combination of the hardness and corrosion resistance is exhibited for the alloy treated with the CDCT twice.

Microstructure characteristics and mechanical behavior of AA2099 Al–Li alloy with no pre-existing Li-containing precipitates (AA2099-1 sample), pre-existing δ′ precipitates (AA2099-2 sample), pre-existing T1 phase (AA2099-3 sample) and pre-existing T2 phase (AA2099-4 sample) are systematically investigated via isothermal uniaxial compression at 250 °C in the present study. Experimental results demonstrate that at the onset of plastic deformation, dynamic precipitation of small-sized T1 phase occurs rapidly within AA2099-1 sample, while it will be hindered within AA2099-2 sample. The increasing plastic strain benefits to dynamic precipitation of small-sized T1 phase in AA2099-2 sample. Consequently, AA2099-1 and AA2099-2 samples possess similar and intermediate mechanical behaviors. In terms of AA2099-3 sample, the existence of large-sized T1 phase results in the maximum yielding stress. However, some regions within these large-sized T1 precipitates are suspected to be sheared by cross-slip, leading to the destruction of crystallographic structure and the formation of Al matrix intervals. This aspect is responsible for the gradual degradation in true stress-strain curve after peak stress. As for AA2099-4 sample, dynamic precipitation rarely happens during plastic deformation and the interaction between dislocation and the pre-existing T2 phase belongs to Orowan looping, resulting in the minimal mechanical response. Besides, AA2099-1 sample possesses the average minimum deviation angle (MDA) of ~ 16.5° between the loading direction and the crystal direction, whereas AA2099-4 sample owns the average MDA of ~ 7.5°. The difference in MDA is mainly attributed to δ′ phase and T1 phase, which will separately accelerate and postpone the rotation of orientation towards the crystal direction.

The Kanbara reactor (KR) process is a mechanical stirring method that reacts hot metal with desulfurization flux; it is a widely implemented desulfurization method in contemporary steel production. This study aimed to develop a new impeller profile for improving the desulfurization efficiency of the KR process. We implemented operational data analysis, a computational fluid dynamics simulation based on the operational data and performed testing and analysis with impeller models on-site a production facility. Operational data from the production facility was gathered over a 3-year period. Seven impeller models with varying impeller blade width (top and bottom), height, inclination, and curvature (curved, straight, and combination) were simulated. The results were analyzed to determine the optimal conditions. A new impeller design was selected for on-site operational testing to investigate the in situ desulfurization efficiency over 350 charges, and the results corroborated the predictions by the numerical simulations. It is expected that the proposed process modification can be successfully used for improving industrial desulfurization efficiency.

Mathematical models are among the new approaches employed to predict the properties of any material under various conditions. Mathematical models are essential for not only understanding the material properties but also estimating the cost of design, product life, and failure criteria of the product. Therefore, in the current investigation, the hot deformation (HD) behaviour and microstructure alteration of deformed AA7150-5 wt% B4C composite was studied through a mathematical model. The new AA7150-5 wt% B4C composite was fabricated through an ultrasonic-probe assisted (20 KHz, 1000 W) stir casting process. The hot compression test was performed on a hydraulic press for various deformation temperatures (623–773 K) and strain rates (0.01–1 s− 1). Based on the outcome, it is inferred that the flow stresses and microstructures of AA7150-5 wt% B4C composite was significantly altered during the hot compression test under various deformation conditions. The constitutive and dynamically recrystallized grain (DRXed) models were developed as a function of various deformation conditions of deformed AA7150-5 wt% B4C composite, which was then applied to forecast the flow stress and grain size behaviour for different deformation conditions. The flow stress and DRXed grain size were obtained through the proposed constitutive and DRXed models are correlated with experimental results, with excellent accuracy. The models developed are reliable to predict the AA7150-5 wt% B4C properties for various conditions.

A novel and efficient deformation methodology, viz., hot-rolling–shearing–bending (HRSB), to introduce a large amount of $$\{ 10\bar {1}2\}$$ extension twins (ETs) and control the texture of the AZ31 magnesium alloy thin sheet was proposed. Microstructure and texture within various regions of the thin sheet fabricated by the HRSB method were investigated by means of electron back-scattered diffraction measurement. The experimental results indicated that using only single pass of HRSB, grains with c-axis//normal direction (ND) in as-received sheet are nearly twinned totally (about 91% volume fraction of $$\{ 10\bar {1}2\}$$ ET), leading to the formation of c-axis//rolling direction (RD) texture component and the disappearance of c-axis//ND texture component. As for the HRS sample which has suffered from rolling–shearing deformation, both a tensile stress component deriving from the shearing deformation and a compressive stress component resulting from the impediment effect of the mould structure are beneficial to activate $$\{ 10\bar {1}2\}$$ ET, the volume fraction of which is about 72%. With respect to the HRSB sample which has undergone rolling–shearing–bending deformation, the further increase in volume fraction of $$\{ 10\bar {1}2\}$$ ET might be mainly related to the resultant compressive stress of the tensile stress derived from the bending deformation and the compressive stress resulting from the impediment effect of mould structure. It would hinder the activation of $$\{ 10\bar {1}2\}$$ ET within twinned areas and promote the migration of existing boundaries of $$\{ 10\bar {1}2\}$$ ET into un-twinned areas.

In this study, interactive alternate forward extrusion (AFE) experiments with varying number of extrusion passes of AZ31 magnesium alloy were carried out. The evolution of microstructure, and texture and their effects on the mechanical properties were studied. The results show that with the increase of loading passes, the grains are significantly refined, and the dynamic recrystallisation (DRX) structure is uniformly distributed in the product, which is the main reason for the increase in microhardness, compressive strength and failure strain. Further, slip and twinning induced DRX behaviour are considered to be the main deformation methods in the early stage of deformation. Whereas continuous DRX is considered to be the main deformation methods for the change in grain morphology in the later stage. During the extrusion process, the deflection angle of the base pole decreases. Finally, the fibre texture is formed; the texture strength is significantly reduced because of the effect of recrystallisation. The AZ31 magnesium alloy interactive AFE process is discussed with respect to the technological experiment and the microstructure deformation, thus providing a vital scientific basis for further application.

This paper reports the creep behavior of a nickel-based single crystal alloy and the creep fracture mechanism under high temperature and low stress was discussed. The creep curves were analyzed with the Kelvin model. The retardation spectra suggest that the involved atoms during creep need more relaxation time to achieve the viscous flow, nevertheless, the creep under the stress of 120 MPa may be caused by the mismatch of dislocation motion and visco-plastic deformation. The fracture morphologies of crept alloys indicate that the nickel base single crystal alloy presents micro-pore aggregation fracture mechanism under the condition of high temperature and low stress creep.

High strain rate rolling (HSRR) is developed to improve the strength, plasticity and stress corrosion resistance of 7050 aluminum alloy simultaneously. The volume fraction of the small-angle grain boundary in the HSRRed alloy sheet is 89.9%. TEM shows that the presence of dislocations and sub-grains promotes the precipitation of the second phase. The alloy in the T6 state has the highest strength (622 MPa) and the biggest elongation to rupture (20.6%), but poor corrosion resistance. The over-aged state shows the best corrosion resistance. The RRA state can achieve the tensile strength equivalent to T6 of 614 MPa, the highest yield strength of 561 MPa and corrosion resistance comparable to the over-aged state. TEM observation shows the existence of sub-grains and dislocations plays an important role in the nucleation of the second phase. The high strength can be attributed to the higher volume fraction of the precipitates, and the high plasticity can be attributed to the higher work hardening rate. The better corrosion resistance can be ascribe to the wider precipitate-free zones at the grain boundary and the presence of the larger size second phase particles.

TiB2 has excellent performances in terms of wear resistance and corrosion resistance, mechanical strength, high elastic modulus and high compressive strength, hardness, but its application is still limited due to its poor manufacturability. It is expected to provide a transforming technology for its application by implementing additive manufacture of TiB2. The main content of this paper is to propose an innovative technology, selective laser alloying (SLA), using elemental powders of Titanium and Boron provides a transforming technology for the application of TiB2 by enabling its 3D forming from a pure simulation perspective. In this paper, a model of the in-situ reaction process is proposed. By considering the concentration distribution of Ti, B and TiB2, the effects of chemical reaction rate and laser power on the evolution of the free solid–liquid interface and species transport are discussed. The laser energy consumed in the SLA process and the energy released by the chemical reaction were theoretically derived. It showed that the heat released from the exothermic reaction between Titanium and Boron is an important energy source which can reduce the energy input and help improve the manufacturing efficiency of the SLA process; the chemical reaction rate has a significant influence on the concentration distribution of Ti, B and TiB2; the volume and existence time of molten pool and the heat source of reaction strongly relies on the chemical reaction rate and the laser power.

Aiming at the problems of poor hardenability and low mechanical strength of 45 steel after quenching and tempering at normal pressure, 45 steel was quenched and tempered under high pressure. The microstructure of 45 steel after high pressure quenching and tempering was analyzed by optical microscope, scanning electron microscope and transmission electron microscope, its hardness and compressive strength were tested by hardness tester and electronic universal testing machine, and compared with samples treated by the same process under atmospheric pressure. The results show that uniform and compact tempered sorbite can be obtained after high pressure quenching and tempering of 45 steel, and the precipitated granular carbides are finely dispersed, thus improving the mechanical properties of 45 steel. Under a pressure of 3 GPa, quenching at 900 °C for 15 min and 550 °C for 60 min tempering, the hardness and compressive yield strength of 45 steel were 36.3 HRC and 971 MPa, respectively, which were respectively 25.17% and 20.77% higher than the corresponding values obtained with the same process under atmospheric pressure quenching and tempering. This work provides a new method to effectively improve the mechanical properties of 45 steel.

This paper optimizes experimental parameters on controlling corrosion performance of the Mg-rare-earth alloys with long period stacking ordered structure using response surface methodology. Different NaCl concentrations, temperatures, and varying pH values are selected as input parameters. The corrosion current density (icorr) and open circuit potential (OCP) are used as the multiple responses to evaluate the corrosion performances. The corrosion surface morphology and corrosion mechanism of the Mg alloys are also investigated by scanning electron microscopy for the optimization. Analysis of variance (ANOVA) has given the impact of individual factors and interactions on the corrosion rate. The results indicated that the three test parameters had significant impacts in controlling the corrosion behavior of Mg alloy. Moreover, the increased NaCl concentration decreased the pitting potential (Epit) of the target materials. Filiform corrosion can be detected in high pH solutions, whereas the matrix suffered from severe dissolution phenomenon in low pH solutions. High temperature aggravated the local destruction and dissolution of the protective film. The interaction of the experimental parameters showed a sizable influence on corrosion performance.

In this study, route Bc of the equal channel angular pressing (ECAP) method has been successfully applied to the Al–Si–Cu alloy at 400 °C. Scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) were used to analyze the microstructure. Texture evolution was studied by the X-ray diffraction (XRD) technique. The microstructural results showed that at least four passes of route BC need to access uniform distribution of fine intermetallic compounds (IMCs) and eutectic silicon particles (ESPs). The particle stimulated nucleation (PSN) and continuous dynamic recrystallization (CDRX) are two important mechanisms to refine the aluminum matrix in Al–Si–Cu alloy. The texture results revealed that owing to a change in the rotation direction of route BC in consecutive passes, this process led to creating different types of textures, in both qualitative and quantitative senses. The A*1Ѳ and A*2Ѳ were the strongest texture components after the fourth pass of route BC. Regardless of route A, the route BC-ECAP process led to strengthen the {100}〈001〉 and {011}〈100〉 components and weaken the {001}〈310〉 component. Three components, {100}〈110〉, {021}〈501〉, and {013}〈313〉 were developed by route BC. The effects of route BC on texture homogeneity were also studied.

In this study, a multi-stage sandblasting and acid-etching processing method is used to prepare a 304 stainless-steel surface with a loose structure that has the composite properties of superhydrophobicity, low adhesion, anti-icing ability, self-cleaning behavior and corrosion resistance. The surface morphology and chemical constituents of this structure are characterized by scanning electron microscopy and X-ray diffraction, respectively. The results show that the micro-scale roughness and different degrees of porosity in this structure play a key role in its superhydrophobicity. The anti-icing properties and corrosion resistance are characterized by contact-angle measurements and electrochemical workstation analyses, respectively. The results show that superhydrophobicity has positive effects on surface self-cleaning, anti-icing properties and corrosion resistance of 304 stainless-steel.

Conventional friction stir processing (FSP) and ultrasonic-assisted friction stir processing (Ua-FSP) were applied to modify the microstructure and enhance the mechanical properties of as-cast A356 aluminium alloy. A series of experiments with different processing parameters were conducted in these two processing methods. Forming characteristics, grain-refinement, and mechanical properties in FSP and Ua-FSP were compared to determine the effect of ultrasound. The results revealed that ultrasound improved the grain-refinement level in both grain size and grain uniformity. Further, the effect of ultrasound on microstructural evolution was more significant with relatively high processing heat-input. Ultrasonic vibration also positively affected the hardness, tensile strength, and elongation.

In this study, the Ti6AI4V alloy, which is used as an implant material in the medical field, was joined with the laser welding method at different welding speeds. The bioactivity features of the Ti6AI4V alloy and its samples joined at different welding speeds were determined by immersing in a simulated body fluid (SBF) for 1, 7, 14, 21 and 28 days. The hydroxyapatite (HA) formation on the surfaces of the samples was determined by calculating the weight gain. The weight loss was calculated by removing the HA from the surface after bioactivity testing. The corrosion rates of the samples were also determined according to the weight loss. In addition, the characterization of the HA formed on the surfaces of the samples was performed. As a result of the investigations, it was determined that the increase in laser welding speed, and therefore the decrease in heat input, positively affected the bioactivity and biocorrosion features of the Ti6Al4V laser welded joints. It was determined that the particle sizes of the HAs of the laser weldments increased with lower heat inputs. It was also observed that the amount of HA nucleated on the laser-welded samples increased in accordance with the increase in the laser welding speed. The laser welded samples that were welded at higher welding speeds and therefore at lower heat inputs, exhibited better biocorrosion behaviors.

Surface mechanical attrition treatment (SMAT) is a method that enhances the mechanical properties of metallic materials by generating a thin nanostructured layer on the top surface. In this study, single-shot impact behavior was modeled for the 7075-T6 aluminum alloy to reach maximum values of equivalent stress, plastic strain, deformation depth, residual stress depth, and residual stress. Finite element simulations have been carried out to analyze the effect of selected parameters on stress and strains in the component. For simulating the SMAT process, a rigid sphere on a rectangular component is modeled using ANSYS/AUTODYN explicit dynamic solver. The plastic deformation process during SMAT was analyzed according to shot velocity and diameter with a dynamic explicit finite element method (FEM). The response surface methodology was used to evaluate the parametric results for the SMAT process. In addition, deformation behavior was evaluated after a single-shot impact according to the restitution coefficient.

In this study, SAE 1020 steel samples were boronized at 850 °C for 4 h with different boronizing mixtures by powder-pack boronizing method. H3BO3 or Na2B8O13 was used as the boron source, KBF4 or NaBF4 was used as the activator and SiC was used as the diluent. Thus, 4 different boronizing mixtures (M1-M4) were prepared. Thickness, morphology and phase structure of the formed boride layers were studied by X-ray diffraction and microstructural analyzes. The single phase (Fe2B) boride layer with saw-tooth morphology was formed on surface of the samples. The thickest boride layers were obtained by using M1 and M2 boronizing mixtures. Microhardness measurements were performed to determine hardness of the 3 zones (core, transition zone and boride layer). The means of boride layer hardness of the samples were compared according to 95% Confidence Intervals analysis. It was determined that the average hardness value of the boride layers was about 1475 HV. Wear tests were fulfilled by ball on disc type wear test method under dry sliding condition and at 25 °C. According to the friction coefficient and specific wear rate values of boronized samples, it was identified that the sample SM4 boronized with M4 boronizing mixture has the lowest wear rate (1.64 mm3/N.m) and friction coefficient value (0.63).

The main goals of this work were to manufacture novel Al–Zn extruded alloys by varying the Zn content (0, 10, 20, 30 wt%), investigate the microstructural evolutions, hot deformation, and work hardening behaviour by hot compression test at different temperatures (25 °C, 75 °C, 150 °C, 225 °C, 300 °C). Al–20Zn alloy microstructure revealed α-Al and uniform distribution of (α + η) phases, coherent (α + η) crystals in GBs with casting defect-free surfaces, and effective interactions of pinning dislocations which led to improve mechanical performance of Al–20Zn alloy, as compared to the other alloys. The observed engineering stress–strain curve results revealed the decrease of stress with increasing of temperature due to flow softening, dynamic recovery and dynamic recrystallization. These results displayed also an increase of stress value with increasing of Zn content due to the precipitation of high density (α + η) phase in the matrix and GBs, increasing of forest and mobile dislocations density with strain fields, and the formation of fine dendrites. Work hardening rate (WHR) of extruded samples displayed three stages: stage I, WHR decreased slightly with increasing of temperature up to 75 °C and decreased drastically from 75 °C to 300 °C due to softening; stage II, WHR maintained constant due to balance between dislocation generations and dislocation annihilation; stage III, WHR slightly increased due to strain hardening of (α + η) phase. WHR was observed to increase considerably with increasing of Zn content due to the formation and dispersion of high density of (α + η) phase in the Al matrix and GBs. Deformation micro-localization in terms of different characteristics was examined and reported on the deformed samples after hot-compression test through SEM micrographs.

The microstructural evolution and fire-resistant properties in the weld heat-affected zone (HAZ) of Mo and Mo + Nb-added fire-resistant steels were investigated. For this purpose, three Fe-0.1 wt%C-1.5 wt%Mn-0.1 wt%Si steels containing various Mo and Nb contents were prepared. HAZ samples were experimentally simulated using a Gleeble simulator at a welding heat input of 30 and 300 kJ/cm. The yield strength of the HAZ samples was higher than those of base steels at both room temperature and 600 ℃, whereas a greater decrease in the yield strength at 600 ℃ compared to that at room temperature occurred in the HAZ samples than in the base steels, indicating that the fire-resistance deteriorated in the HAZs as compared to the base steels. This is due to the formation of hard phases such as bainite and martensite in the HAZs, i.e., bainite and martensite phase have very high yield strength with high dislocation density at room temperature, while their strengths decrease rapidly at high temperature due to a great annihilation and recovery of dislocations at high temperature. In addition, the fire-resistance of the HAZ improved as the heat input was increased. The alloying of Mo and Nb improved the fire-resistance of both the base steels and the HAZs. Finally, the changes in the microstructures of the base steels and the HAZs upon alloying and the heat input and corresponding effects on the fire-resistance were carefully explored and discussed through transmission electron microscopy analyses, atom probe tomography analyses, and calculations of continuous cooling transformation diagrams.

The microstructure and high temperature properties of the AXE622 Mg alloy were investigated after the conventional and semisolid casting processes. The tensile test was conducted at room temperature, and 473 K. Impression creep test was performed at a temperature range of 423–498 K under the stress range of 450–600 MPa. The microstructure of the conventional and semisolid alloys contains α-Mg dendrites, the eutectic phase, secondary phases including (Mg–Al)2Ca, eutectic Mg17Al12, and Al11RE3. During semisolid processing, coarse dendrites of the α-Mg became fine, globular, and Rosetta shape. The average length of the secondary phases in the semisolid alloy decreased from 4.21 to 2 μm and the average grain size of the α-Mg reduced from 113 to 96 μm. Semisolid processing caused a significant improvement in the tensile and creep resistance of the AXE622 Mg alloy. The stress exponent for creep was calculated in the range 5.6–7.7 for the conventional alloy and in the range 10.3–11 for the semisolid alloy. The activation energy for conventional and semisolid alloy was determined as 71.4 kJ/mol and 78.3 kJ/mol, respectively. It was concluded that the dominant creep mechanism in the conventional alloy was the grain boundary diffusion-controlled dislocation climb, while in the semisolid alloy was the power-law breakdown.

A hot pressing method was used to obtain a layered composite consisting of alternating layers of AISI 439 type steel with a high nitrogen content (0.8%) and Fe-20% Cr-5%V alloy with a low nitrogen content (less than 0.02%). Annealing of the composite at T = 700–850 °C after hot pressing leads to diffusion of nitrogen from the nitrided AISI 439 layers into the Fe–Cr–V layers, the formation of diffusion zones containing dispersed vanadium nitrides in the Fe–Cr–V layers and the formation of diffusion zones with a low nitrogen content in the AISI 439 layers. A tendency towards a decrease in the sizes of the vanadium nitride particles with decreasing annealing temperature was revealed. Annealing at T = 750 °C increases the plastic characteristics and reduces the strength characteristics of the composite compared to the state after hot pressing. The presence of dispersed vanadium nitrides precipitated in the composite structure during annealing increases the strength of the composite by 15%.

This study was aimed to determine the main cause of lance fracture in a smelting furnace of the Mitsubishi continuous process for Cu production. Investigation of lances used in field operations, thermodynamic analysis and laboratory experiments were conducted. By analyzing the lances, damaged surface of the lances and penetration of matte components into the lance were observed. The depth of damage was strongly dependent on the lance height which was related to temperature. To determine the temperature of the lance fracture, thermodynamics calculations and laboratory experiments were conducted. Both results showed that the formation of Cu liquids above 1100 °C could be the main cause of lance fracture during operation of Cu smelting furnaces of the Mitsubishi process.

Galvannealed (hot dip galvanized and annealed) dual phase (DP600) steel and interstitial free (IF) steel are two of the widely used materials in automotive industries owing to their high specific strength, toughness, formability and corrosion resistance. This inevitably requires their joining to form larger components. Resistance spot welding has emerged as the predominant welding technique for joining of sheet metals in automotive industries. There are complexities regarding microstructural variation of the fusion zone and across heat affected zones during spot welding of fundamentally dissimilar steels. This is further aggravated by the prospect of zinc redistribution during the welding process. Current study presents the evolution of microstructure in different zones of welding in IF and DP600 steel. Micro-hardness profiles and electron back scattered diffraction studies were performed. Furthermore, redistribution of elements in different welding zones is studied using electron probe micro analysis. The effect of welding current and time on the nugget size and the strength of the weld during tensile–shear is determined. It was observed that there was an increase in nugget diameter and maximum load bearing capacity of the joint with an increase in heat input, until the occurrence of expulsion. Furthermore, critical nugget diameter for pull-out failure was determined and existing empirical models were verified for the applicability in this case. None of the existing empirical models could predict the critical nugget diameter correctly and thus a new empirical relationship between sheet thickness and critical nugget diameter for zinc coated dissimilar steels has been proposed. Failure behaviour of the spot-welded sheets were studied under tensile–shear configuration under quasi-static and fatigue mode of loading and it showed substantial difference in location of crack initiation and fractographic features. Tensile–shear specimen at optimum welding parameter failed from the base metal of the IF steel side with dimples on the fracture surface, whereas fatigue specimen failed from the heat affected zone of the IF steel side with transgranular striations on the fracture surface.

In this study, the influences of the stress aging process on the electrochemical behaviors toward evaluating corrosion resistance of NiTi shape memory alloys in the in-vitro condition have been investigated. For this approach, the samples have been manufactured by introducing multiple precipitation morphology in the alloy structure via applying different levels of stresses during the aging process. The samples were characterized using multiply electron microscopy, electrochemical methods, X-ray diffraction, and differential scanning calorimetry. Results show that by prolonging aging time from 1 to 5 h and increasing the stress aging level (15–60-150 MPa) the corrosion resistance improves, which is implied a better formation of a protective layer. It seems that homogeneous precipitation of Ni-rich phases under the stress aging process improves the corrosion resistance of the alloy.

The structure, hardness, tensile and wear behavior of Mg–5Sb–xSiC hybrid composites experimented where the amount of SiC particles were 1, 3, and 5 wt% SiCp before and after applying hot extrusion process. Micron size SiC particles were added to Mg–5Sb alloy via stir casting technique to form both Mg3Sb2 and SiC particles in the as-cast microstructures. Although SiC addition reduced the grain size of the Mg–5%Sb in-situ metal matrix composite (MMC), no improvement was observed on ultimate tensile strength (UTS) and the ductility (EL.%) in the as-cast state. The use of the extrusion process led to a remarkable fracturing of Mg3Sb2 intermetallic along the extrusion direction, grain refinement, and reduction in the size of SiC clusters. The optimal amount of SiC was found to be 3 wt%, which reduced the grain size from ~ 827 to ~ 4 µm and promoted the UTS amounts from 120 to 244 MPa for as-cast and hot extruded composites. Besides, the enhancement of yield strength of extruded MMCs was rationalized depending on the grain size compared to the as-cast condition. The fractography of the as-cast composites revealed more cleavage planes in contrast with hot extruded composites, which proved much more dimples. It was also found that the use of hard SiC particles in hybrid composite improved wear properties just in the extruded state. According to observations, in various sliding test conditions, the abrasive, oxidation and delamination are mostly operated in combination.

The 10 μm 10 vol% SiCp/2024Al composites sheet was successfully fabricated by semi-solid stir casting followed with two-step deformation (extrusion and rolling). The two-step thermal deformation solves the sheet rolling formability of the SiCp/2024Al composites produced by stir casting. Compared with the SiCp/2024Al composites prepared by traditional powder metallurgy, this paper innovatively studied the synergistic enhancement between CuAl2 phase and SiCp on the mechanical properties. The result shows that the two-step deformation can significantly improve the uniformity of the distribution of SiCp and CuAl2 phases. At the same time, the average size of the SiCp and CuAl2 phase decreases after the two-step deformation. During the hot extrusion, SiCp has an obvious hindrance to the refinement of the CuAl2 phase. Moreover, the SiCp/2024Al composites sheet exhibits excellent yield strength (295 MPa), ultimate tensile strength (489 MPa), and elongation (10.42%). The performance improvement of SiCp/2024Al after two-step thermal deformation is mainly attributed to the improved interface bonding strength of SiCp-2024 Al matrix, the refined SiCp and the more uniform distribution of SiCp.

A longitudinally varying magnetic field (MF) was applied during cold metal transfer (CMT) welding of Al alloys. The effect of MF on the welding process, macrostructure, microstructure and properties of weld beads was studied. The results showed that the application of MF led to arc expansion and rotation, the droplet transfer frequency decreased, the droplet volume became larger, and the droplets deflected. When the coil current was between 0 and 5 A, the weld beads porosity decreased from 4.47 to 0.26%. And when the coil current was increased to 8 A, the porosity of weld beads also increased to 2.84%. MF reduced the weld depth, wetting angle and weld reinforcement, and increased weld width. With the increase of coil current, the width of primary dendrite arms decreased from 7.75 to 5.01 μm. The area occupied by the Al–Si eutectic was enlarged, and the eutectic was refined. It was also found that the MF slightly increased the hardness of the weld beads, and the hardness distribution was more uniform.

To improve the high-temperature resistance of the key hot-end parts of the steam turbine, NiCoCrAlY coatings were deposited on a 304 stainless steel substrate by laser cladding. The microstructure and high-temperature oxidation behavior of the NiCoCrAlY coatings were analyzed. The results showed that the NiCoCrAlY coatings contained γ/γ′ and β phases, and the microstructure was mainly composed of elongated columnar crystals. In addition, after 100 h of oxidation at three different oxidation temperatures (750, 850 and 950 °C), the coatings showed a relatively low oxidation rate, which was approximately a quarter of the oxidation rate of the substrate. At the same time, the protective Cr2O3 scales were formed on the coating surface. When the oxidation temperature was 850 °C, the FeCr2O4 spinel formed and internal oxidation zone appeared, when the oxidation temperature reached 950 °C, the FeCr2O4 spinel gathered in the local area on the surface of the Cr2O3 scale and the internal oxidation was aggravated. In other words, as the oxidation temperature increased, the Fe element in the matrix formed the FeCr2O4 spinel, which accelerated the consumption of Cr element in the coatings and reduced the overall oxidation resistance of the NiCoCrAlY coatings.

In the present study, different finite element (FE) models were prepared to investigate weld induced residual stresses in thick multi-pass butt welded joint of SA516 Gr. 70 plates. Both 3D and 2D full geometry models and their axisymmetric half models were taken into consideration. The competence of these FE models on the accuracy of predicting residual stress distribution across the weld cross-section was investigated by comparing it with the experimental results. Blind hole drilling technique and deep hole drilling technique were employed to evaluate the surface and through-thickness residual stress distributions, respectively. In addition, the change in volume and yield strength of weld material due to austenitic phase transformation was also incorporated in the material modeling to observe the effect of solid-state phase transformation (SSPT) on the evaluation of residual stresses. Computed residual stresses obtained from different FE models indicate that the 3D FE models procured the best accuracy compared with the experimental results. On the other hand, 2D models can save a significant amount of computational time with reasonable accuracy. Incorporation of SSPT in the 3D FE full model exhibited a better agreement of predicted results with the experimental measurements.

Mechanical alloying is a widely used alternative to the liquid-phase method of embedding reinforcements to manufacture metal matrix composites (MMC). In this research, high-energy ball milling was used to distribute various volume fractions of sub-micron-sized SiCp particles (2, 10, and 20 vol%) in AA2024 aluminum powder alloy, focusing on powder morphology and milling conditions. An increase in the full width at half-maximum and the shifting of peaks at higher angles were observed after mechanical alloying. These examinations were attributed to changes in the lattice parameters of the matrix alloy. It was noted that the temperature and loading pressure during the die compaction stages of MMC powders directly affect the compact density, whereas the volume fraction of SiCp changes hardness. Compression testing, conducted at elevated temperatures to evaluate the plastic properties of the material, showed sufficient ductility characteristics for thermomechanical processing.

In this study, the effect of Mn addition on the corrosion properties and biocompatibility of a new biodegradable Mg–1Ca–2Zn–1RE–xMn alloy (x = 0, 0.3, 0.6, 0.9 wt%) was investigated using Hank’s solution. The main purpose was to achieve a biocompatible alloy with optimum corrosion properties which can be used to fabricate biodegradable implants. Thus a special composition of alloying elements was used. X-ray diffraction analysis revealed that Mn addition does not induce any Mn intermetallic phase. Besides, Mn shifted the solute elements from the grain boundaries toward the matrix. The corrosion resistance of the alloys was efficiently improved by adding Mn, according to the electrochemical measurements. The highest corrosion resistance in comparison with other alloys was observed for the alloy with 0.9 wt% Mn. Moreover, the Fourier-transform infrared spectroscopy test and scanning electron microscope images of the immersed specimens in Hank’s solution, indicate that Mg–1Ca–2Zn–1RE–xMn is a biocompatible alloy as phosphate and carbonate groups are formed on the specimens which are the fingerprint of hydroxyapatite formation.

Herein, the friction stir processing (FSP) method was adopted to modify the microstructure of as-cast nickel aluminum bronze (NAB). The microhardness, cavitation erosion-corrosion mass loss, morphological damage and electrochemical tests were extensively examined. The results show that FSP can refine and uniform the microstructure of as-cast NAB alloy. FSP NAB alloy displays enhanced cavitation erosion resistance in distilled water and artificial seawater, as well as heightened sensitive to corrosive media in artificial seawater. Quantitative analysis of the synergistic effect between cavitation erosion and corrosion shows that pure cavitation erosion components contributions largest for as-cast NAB. In contrast, FSP NAB is greatly influenced by the synergistic effect component. The damaged surface shows that cavitation erosion mechanisms of as-cast NAB in distilled water and artificial seawater are similar, which is not the case for FSP NAB due to the synergistic effect between cavitation erosion and corrosion.

This study emphasizes the effect of ultrasonic surface rolling (USR) on the surface roughness, hardness, and tribological properties of ductile iron under different normal loads. Results revealed that surface roughness was reduced by 96% and surface hardness increased by 37.8% after USR treatment. By increasing normal load, the average friction coefficient of the USR-treated specimens decreased, but the wear rate of both USR-treated and untreated specimens increased, mainly because the dominant wear mechanism changed. The average friction coefficient of the untreated specimen (~ 0.32) was much higher than the USR-treated specimen (~ 0.24) when the normal load was 30 N. However, the wear rate of the USR-treated specimen was larger than that of the untreated specimen when the normal load was greater than 20 N because the higher hardness abrasive particles on the worn surface of the USR-treated specimen not only accelerated abrasive particle wear, but also caused more severe adhesive wear.

The present work examines the formation of a corrosion protective coating containing intermetallic phases on magnesium alloy substrates. The protective coating was formed on the surfaces of commercially pure magnesium (cp Mg) and AZ31B magnesium alloy by vacuum thermal evaporation of commercially pure aluminium (cp Al) and a subsequent heat treatment of the sample. This coating was continuous, homogenous and its microstructure was a eutectic phase composed by clusters of α-Mg surrounded by β phase (Mg17Al12). This eutectic-type coating provided 168 and 504 h of protection inside the salt spray chamber for the cp Mg and AZ31 alloy samples, respectively. To achieve this, it was required to deposit at least 5.5 µm of cp Al and then perform a combined thermal treatment involving heating the samples to 583 K for 60 min and then raising the temperature to 693 K for 5 min.

In general, the martensitic transformation in metastable austenite grain in steels during nanoindentation investigation will induce strain burst, also commonly referred as pop-in. However, it is found that the occurrence of pop-in depends on the position of transformed martensite. Different from the martensite transformed beneath the indenter, the martensite transformed adjacent to the indenter may not necessarily lead to an obvious pop-in. Nevertheless, the formation of martensite adjacent to the indenter can alter the mechanical behavior of the austenite phase. Thus, the present work demonstrates that in addition to the detection of pop-in, an investigation on the change of mechanical behavior of austenite phase is necessary to characterize the martensitic transformation during nanoindentation investigation.

A new image-processing method based on block-gradient segmentation was proposed to measure the volume fraction of mechanical twins in metallographic images. The processing results showed that this automatic method could be used for rapid and effective measure of the twin-volume fractions of twinning-induced plasticity steels in metallographic images under different strain conditions. The entire processing time for each image is relatively short, which would benefit researchers processing a large number of metallographic images. This method may pave a way to develop a simple, effective plug-in to measure rapidly the twin-volume fractions in the software for metallographic observations, and it would be beneficial for preliminary analysis of microstructural evolutions and subsequent characterization of mechanical twins by high-resolution microscopy using electron microscopy.

A novel nickel-based single crystal superalloy with low density had been designed and the creep deformation mechanisms of the experiment alloy under two conditions (1050 °C/200 MPa and 1100 °C/137 MPa) had been systematically discussed. The topological inversion had been observed after fracture under the above two conditions. The effects of temperature and stress on creep life of the experiment alloy had been found no significant difference under the two conditions. It was indicated that the small decrease in temperature exerted limited influence on the creep behaviors of single crystal superalloys in the range of high temperature.

In the present study, a Mg–8Al–0.5Zn (AZ80) Mg alloy was subjected to water quenching and furnace cooling from the solution treatment temperature of 390 °C. Subsequently, all the samples were subjected to aging treatment at 250 °C. The precipitation behavior, aging response and fracture phenomenon of the AZ80 Mg alloy were evaluated to establish the correlation among the cooling rates after solution treatment, microstructural features and mechanical properties. Scanning electron microscopy depicted a very distinct precipitation behavior of aged specimens. The observed variation in the aging curves was rationalized based on this. Fractographic analysis on the as-solutionized and aged alloys revealed that the initiation of fracture (i.e., intergranular or transgranular) was dictated by the presence of microstructural features, such as precipitates (continuous and discontinuous), twins and grain boundaries. The fracture strain was correlated with the number density and size of voids formed during tensile loading.

Due to the high exothermic characteristic of NiAl during the reaction synthesis process from Ni–Al elemental powders, the NiAl intermetallic melts frequently, and the specimens are difficult to maintain their original shape, which leads to the inhomogeneity of the pore size and morphology. To tackle this problem, porous NiAl intermetallic monolith with controllable shape and pore structure was prepared through thermal explosion (TE) using NaCl as space holder. The TE behavior was recorded, and the effect of the volume fraction of NaCl on the phase composition, macroscopic feature, pore morphology and open porosity were investigated. The results showed that NiAl was the main phase in the products, and the specimen was free from cracking or deforming when NaCl content reached 30 vol%. The interconnected channel and pore windows were formed, and the open porosity was improved greatly to 63% by adding 50 vol% NaCl. The leachable space holder route provides a simple way to control the shape, pore structure and open porosity of the synthesized porous NiAl intermetallic. The use of NaCl as space holder reduced the combustion temperature of NiAl porous intermetallic compounds and kept the macroscopic shape intact.

High entropy alloys (HEAs) have received tremendous attention in different applications because of their excellent corrosion resistance and superior mechanical properties. In the present work, a novel TiNbMoMnFe high entropy alloy system was synthesized and deposited on AISI 316L by DC magnetron sputtering system. The microstructure of the resulting thin film was evaluated by grazing incidence X-ray diffraction and field emission electron microscope. It was found that the thin film microstructure is composed of a crystalline solid solution (grain size of 76 nm) and an amorphous phase. The electrochemical investigations in Ringer’s solution revealed that a thin film of 670 nm thick high entropy alloy has a low corrosion current density of 0.024 μA cm−2, approximately 30% lower than that of the uncoated 316L. Meanwhile, the HEA thin film showed the highest pitting corrosion resistance and stability of the passive film. The wettability examinations exhibited that the coated sample has a high contact angle of 90° in contrast to 60° for the uncoated ones. In summary, the TiNbMoMnFe high entropy alloy thin film shows great potential for use in biomaterial applications.

Metal additive manufacturing (MAM) is an emerging technology to produce complex end-use metallic parts. To adopt MAM for manufacturing numerous engineering parts used in critical applications, a thorough understanding of the relationship between the complex thermal cycles in MAM and the unique heterogeneous microstructures of MAM parts need to be established. This review article provides a comprehensive overview of the evolution of heterogeneous microstructures in MAM parts, including melt pool boundaries, heterogeneous grain structure, sub-grain cellular structure, matrix supersaturation, segregation, phase transformation, oxides formation, and texture. The evolution of residual stresses and the anisotropy in MAM parts and the post-MAM heat treatment effects on the microstructural evolution are also discussed. This review covers the microstructural aspects of most engineering materials in particular steels, high entropy alloys, aluminum alloys, titanium alloys, nickel-base superalloys, and copper alloys, with a primary focus on the parts manufactured using selective laser melting, direct energy deposition, and electron beam melting processes.

Carbon materials, like carbon fiber, carbon nanotubes and graphene, were widely used as promising reinforcements to strengthen aluminum matrix composites (AMCs). The dispersion of reinforcement in matrix and interface wettability between matrix and reinforcing phase have been key factors affecting AMCs properties. In this study, electroless copper-coated carbon fibers reinforced aluminum (Cu-Cf/Al) composites were prepared by spark plasma sintering processing followed by heat treatment. Microstructure and mechanical properties were investigated. Microstructure observation indicated that fibers distributed uniformly in the composites containing up to 9 wt% copper-coated carbon fibers (Cu-Cf). In addition, an interfacial layer of 50 nm thickness was formed between the fiber and Al matrix due to mutual diffusion of Cu and Al atoms. Vickers hardness, tensile strength and bending strength of 9 wt% Cu-Cf/Al composite increased from 40 to 93 HV, 59 to 190 MPa and 110 to 326 MPa, respectively, compared to Al matrix. The improved mechanical properties are ascribed to the synergistic effect of dispersion, precipitation and solution strengthening. However, the elongation of composite decreased as compared to that of Al matrix. Moreover, Cu-Cf/Al composite exhibits superior corrosion resistance over uncoated carbon fiber/Al composite but less than Al matrix.

In this study, a simulation-based examination on the deformation mechanism in the friction stir welding (FSW) process is conducted, which may not be efficiently feasible by experiment due to severe deformation and rotation of material flow near a tool pin. To overcome the severity of distortion of plastically deforming finite element meshes in the Lagrange formulation, and an over-simplified elastic-plasticity constitutive law and contact assumption in the Eulerian formulation, the arbitrary Lagrangian–Eulerian (ALE) formulation is employed for the finite element simulations. Superior accuracy in predicting the temperature profiles and distributions of the friction stir welded aluminum alloy workpiece could be obtained compared to the results of Eulerian based simulations. In particular, the ALE based simulations could predict the sharper gradient of temperature decrease as the distance from the welding zone increases, while the Eulerian based model gives more uniform profiles. The second objective of the study is to investigate the coupling of simulation-based temperature histories into the strength prediction model, which is formulated on the basis of precipitation kinetics and precipitate-dislocation interaction. The calculated yield strength distribution is also in better agreement with experiment than that by the Eulerian based model. Finally, the mechanism of the FSW process is studied by thoroughly examining the frictional and material flow behavior of the aluminum alloy in the welded zone. It is suggested that the initially high rate of temperature increase is attributed to frictional heat due to slipping of material on the tool surface, and the subsequent saturated temperature is the result of sequential repetitive activations of the sticking and slipping modes of the softened material. The sticking mode is the main source of plastically dissipated heat by the large plastic deformation around the rotating tool pin. The present integrated finite element simulation and microstructure-based strength prediction model may provide an efficient tool for the design of the FSW process.

Effects of evolution in anisotropy during plastic deformation under strain path changes on the formability and failure were investigated in the present study. The evolution in anisotropic property of the extra deep drawing steel was considered by implementing the non-quadratic anisotropic yield function Yld2000-2d as a function of effective plastic strain, and the corresponding forming behaviour in two-step forming processes was analysed. For the strain path effect, pre-strain was applied under biaxial mode using Marciniak in-plane stretch forming set-up, followed by the secondary deformation using the out-of-plane stretch forming tool. For failure prediction of the proposed two-step forming, different failure limit approaches were investigated. First, a strain based forming limit diagram (FLD), proposed as the Marciniak–Kuczynski model was modified to include the evolution in anisotropic yield function. The dynamic shift in FLD was also determined by taking strain path change into consideration. In addition, the influence of evolution of yield function on the strain path independent failure limit criteria was also assessed in terms of stress based forming limit diagram. Finally, the prediction accuracy of the failure limit criteria was compared among different models in terms of failure location and limiting dome height (LDH). It was observed that the incorporation of evolution in anisotropic yield surface improved the prediction of formability in terms of the LDH and strain distribution for the investigated material.