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During contact flash welding of rails, the metal is heated and continuously cooled in the zone of thermal influence. Accelerated heating and subsequent intensive cooling, implemented by the pulsed flashing-off method, lead to the formation of quenching structures. Subsequently, during the operation of the rails welded joint, this leads to the formation of cracks and to brittle destruction. We have investigated the possibilities of using contact heating after welding to avoid the formation of quenching structures in the metal of the welded joint made of R350LHT rail steel. The thermal cycles during welding and subsequent contact heating were recorded. The regularity of formation of the weld metal structure was established including the zone of thermal influence during pulsed contact heating for R350LHT rail steel. It is shown that contact pulse heating slows down the welded joint cooling and prevents the formation of quenching structures. However, contact pulse heating when using suboptimal modes can also lead to the opposite effect. It is determined that with a significant investment of heat by contact heating, cooling rate of the metal exceeds the critical one, transformation process passes through a diffusion-free mechanism with the formation of martensite coarse-grained structure. The use of thermokinetic and isothermal diagrams of austenite decomposition at known thermal welding cycles allows us to significantly narrow the search limits for optimal modes of contact butt welding of railway rails and subsequent contact heating. The use of optimal contact heating modes makes it possible to obtain a minimum length of heat-affected zones with reduced hardness without the formation of quenching structures in the welded joint of railway rails.

A two-level control system for the temperature mode of smelting, out-of-furnace processing and preparation for casting of low-carbon steel G/ET is proposed in the conditions of BOF shop-2 of JSC “United West Siberian Metallurgical Combine”. Depending on the technological scheme, it is possible to design various control systems for the steelmaking complex with sequential, parallel and combined inclusion of individual operations and processes. The control system of a sequential group of objects is considered on the example of steel G/ET. The control system includes an external control loop that allows coordinated control of the shop departments by optimizing the mode of technological process conducting at the facility, taking into account the actual operation performed at the previous facility. The implemented nonparametric algorithm of dual control allows the decision-maker to perform joint operational adjustment of control actions for local control loops. The temperature mode of the melts of low-carbon steel G/ET is analyzed and it is revealed that the processing time of the steel ladle at each stage of the BOF – CCM technological route has a significant impact on the steel temperature mode. In accordance with this, the criteria for temperature control quality are formed. The results of computational experiment showed that the introduction of a control unit with a decision-maker contributes to the rational control of metal temperature mode in the BOF – CCM site, and as a result, obtaining a given chemical composition and temperature of steel within narrower limits. It allows one to eliminate deviations from the contact schedule of the main units, and to increase the number of melts in the series and the rate of continuous casting.

Spent electroplating solutions contain small amounts of Pd(II). Cementation of Pd(II) with zinc metal powder is practiced to concentrate the Pd. Dissolution of the cemented Pd metal is necessary to recover pure Pd metal or compounds. In this work, the leaching behavior of Pd metal in inorganic acid solutions (hydrochloric and sulfuric acid) in the presence of an oxidizing agent such as H2O2, NaClO3, or NaClO was investigated. To determine the optimum conditions for Pd leaching, experiments were conducted by adjusting the concentration of the acids and oxidizing agents, reaction temperature and time, and pulp density. Complete leaching of Pd was possible using a hydrochloric acid solution with 3 kinds of oxidizing agents, whereas only NaClO was effective in the leaching with sulfuric acid solution. The chloride ions of HCl and NaClO3/NaClO play an important role in enhancing the leaching of Pd, due to the formation of Pd chlorocomplexes and by decreasing the reduction potential of Pd(II). Compared to H2O2, NaClO3 and NaClO showed some merits as oxidizing agents in terms of reaction time, temperature and low acid concentration. Based on the optimum leaching conditions of single Pd metal, the conditions for the complete leaching of Pd and Zn from the metallic mixtures were obtained.

Compound field–assisted laser cladding is an advanced laser processing technology. In this paper, the influence mechanism of single physical field parameters of electromagnetic-ultrasonic compound field–assisted laser cladding on the cladding layer as well as the parameter optimization of compound field–assisted laser cladding are investigated. The Box-Behnken design response surface methodology method is used for experimental design. Through the response surface modeling analysis, it is found that the ultrasonic power has the greatest influence on the microhardness of the cladding layer. For the wear volume of the cladding layer, as the ultrasonic power increases, the wear volume increases and the wear resistance of the cladding layer decreases. Besides, a smaller ultrasonic power and a larger DC current value can obtain a cladding layer with a smaller wear volume. The optimal combination of physical field parameters was obtained through response surface methodology parameter analysis and experimental verification.

The hot cracking susceptibility in the Trans-Varestraint test was evaluated using the nominal strain calculated using the curvature radius of a bending block and the thickness of a specimen based on the theory of material mechanics. The nominal strain was calculated using the material properties at room temperature. Thus, in the Trans-Varestraint test, the non-uniformity of the strain around the weld part due to the temperature distribution is not considered. Therefore, the strain in the Trans-Varestraint test cannot be evaluated correctly. The aim of this study is to reveal the loaded strain at the weld metal to understand the evaluation of hot cracking susceptibility in the Trans-Varestraint test. The loaded strain around the trailing edge of the weld pool of pure iron was measured in-situ using a high-speed camera and high-resolution optical lens. The results of strains measured using image analysis and the finite-element method at the center of the weld bead were compared. Accordingly, it was clarified that the strain was concentrated on the weld part owing to the bending occurring along the weld line, and the strain exceeding the nominal strain was loaded to the trailing edge of the weld pool.

Significant cost and time savings may be realised if multiple weld repairs are undertaken at the same location during the long-term maintenance of naval vessels. Consequently, this investigation simulates full-thickness hull welds, which are required to facilitate the removal and subsequent replacement of hull sections, by assessing the effects of 4 reoccurring weld repairs on a propriety quenched and tempered steel used for naval applications. Optical metallography, electron backscattering diffraction (EBSD), hardness maps, Charpy impact, and dynamic tear tests were conducted. A combination of real weld repairs and Gleeble heat-affected zone (HAZ) simulations were undertaken to characterise the effects of repeated thermal cycles on the microstructure and toughness of different sub-HAZ regions. When the intercritical reheat temperature was just above the AC1 lower critical transformation temperature, the impact toughness was substantially reduced. This includes the fine-grained HAZ where high toughness is typically expected. The low toughness was attributed to the promotion of fracture initiation via debonding between the matrix and second phase which formed at prior austenite grain boundaries. Compared to the original toughness, the application of multiple repeat welds or multiple simulations of the same sub-HAZ thermal cycle did not deteriorate toughness nor noticeably alter the final microstructure.

The laser-MAG hybrid welding in horizontal-vertical (PC) position was used to study the effect of different groove types on the quality of a root weld. Six combinations of bevel angles (50° + 0° (represents the groove angle of upper plate and lower plate respectively), 45° + 5°, 40° + 10°, 35° + 15°, 30° + 20°, and 25° + 25°) and root face sizes of 2 to 4 mm were designed. Hannover analyzer was used to collect electrical signals to analyze the stability of the horizontal-vertical position welding process. The results show that different combinations of groove angle have achieved one-sided welding with root formation. The groove angle has an obvious effect on the weld inclination and molten weld metal flowing down. The combination of bevel angles in which that of the lower plate is smaller than that of the upper plate was more conducive to avoid welding defects such as weld inclination and molten weld metal flowing down. The best groove angle combination was 30° + 20°, which allowed one-sided welding with root formation using a 4-mm root face.

In this paper, dissimilar joining of NbSS/Nb5Si3 composites to GH5188 Co-based superalloy was performed by using two commercial Ni-based brazing filler alloys, BNi-2 and BNi-5 fillers. The interfacial microstructures of the brazed joints were investigated by scanning electron microscope equipped with an X-ray energy dispersive spectrometer. Three-point bending test was also conducted. When brazed with BNi-2 filler alloy at 1020°C for 15 min, typical reaction products across the brazing seam could be identified as NiSS, borides, Ni3Si+Nb3Si, and (Nb,Ti)2Ni phase. Due to the physical and chemical mismatch between the dissimilar base materials, some cracks were observable at the NbSS/Nb5Si3 composites side. The joint strength was only 60 MPa. While brazed with BNi-5 filler alloy at 1160°C for 15 min, the interfacial reaction became more sufficient, and the joints exhibited an average bending strength of 272 MPa.

This study aims to evaluate the weldability of dissimilar welds with the Inconel 625 and the Hastelloy C-276 nickel-based alloys deposited on ASTM A36 and AISI 1045 carbon steel plates. The welds were carried out by the GMAW process and evaluated by the Trans-Varestraint test. The test results were statistically evaluated, and Fusion Zone solidification processes were simulated in JMatPro software using several dilution levels. The analysis of variance (ANOVA) test results showed that the two different base metals did not affect the weldability of Inconel 625. However, the Hastelloy C-276 alloy showed a significant drop in weldability with the AISI 1045 steel compared to the ASTM A36. The results of the Hastelloy C-276 as the filler metal and the AISI 1045 steel as the base metal showed greater susceptibility to solidification cracking than all the other pairs tested, according to the Trans-Varestraint test. Moreover, the ANOVA test results indicated that the different heat input levels did not influence the sets’ weldability; this was probably because there was only a tiny variation in the dilution levels. The solidification process simulation indicates that higher dilution levels promote the precipitation of a larger secondary phase fraction.

A novel magnesium (Mg) production process utilizing an electrolytic method was investigated for the direct reduction of magnesium oxide (MgO). Electrolysis of MgO was carried out with an applied voltage of 3.0 V using a copper (Cu), silver (Ag), or tin (Sn) cathode and carbon (C) or platinum (Pt) anode in magnesium fluoride (MgF2)−calcium fluoride (CaF2)−sodium fluoride (NaF) at 1273 K or MgF2− lithium fluoride (LiF) at 1083−1093 K. After the electrolysis of MgO in MgF2−CaF2−NaF molten salt, Mg alloys such as Mg2Cu, Cu2Mg, or Mg2Sn phases were produced with current efficiencies of 75.8−85.6% when the concentration of Mg in Mg alloys was 9.1−14.6 mass%. In addition, when the electrolysis of MgO was conducted in MgF2–LiF molten salt, Mg alloys such as Mg2Cu or AgMg phase were produced with current efficiencies of 76.2−81.7% when the concentration of Mg in the Mg alloys was 12.5−13.2 mass%. In addition, to produce high-purity Mg metal from Mg alloys, vacuum distillation was conducted. When vacuum distillation was conducted at 1100−1400 K for a duration of 5 h, the concentration of Mg in the Mg alloys feed decreased from 30.2−34.1 mass% to 0.64−1.75 mass%, and Mg metal with a purity of 99.998−99.999% was obtained under certain conditions. Therefore, the molten salt electrolysis using liquid metal cathode (MSE-LMC) process developed here is feasible for the direct reduction of MgO using an effective and environmentally sound method.

The present study is aimed to investigate the effects of zinc electroplated coating and hot dipping at 480 °C on the microstructure and mechanical properties of pure aluminum/40NiCrMo2-2 steel bimetal interface produced by compound casting at 780 °C. Accordingly, microstructural studies and interface shear strength were determined using optical microscope, scanning electron microscope, and push-out test. Results showed that the interface layer in all the samples, independent from the coating type, is composed of two sub-layers of Fe2Al5 and FeAl3. Furthermore, the linear analysis results and elemental distribution map of the interface indicated that no considerable amount of zinc was present in the interface of the samples. Based on the results, the maximum strength was related to the electroplated sample with the value of 45.1 MPa, while the hot-dipped sample had the strength of 37.5 MPa, which was attributed to the formation of interface layer with less defects in the electroplated sample.

An isothermal diagram of decomposition of supercooled austenite of R350LHT steel was constructed based on the results of dilatometric, metallographic and hardness analysis of this decomposition during continuous cooling and under isothermal conditions. When comparing the thermokinetic and isothermal diagrams, it was found that the thermokinetic diagram plotted during continuous cooling shifts downward and to the right in comparison with the isothermal diagram. This result is fully consistent with the known regularities. During the research, the critical points of R350LHT steel were determined: Ас1 = 711 °С; Мn = 196 °С. This isothermal diagram was used to determine the temperature of the minimum stability of overcooled austenite, which was 500 °C. Under isothermal conditions, pearlite-type structures appear in the temperature range from 700 to 600 °C. At 550 °C, a mixture of pearlitic and bainitic structures is formed. In the temperature range from 500 to 250 °C, bainitic structures are formed: at 500 – 400 °C – upper bainite; at 350 ° C – a mixture of upper and lower bainite; at 300 – 250 °С – lower bainite. Almost in the entire studied temperature range of overcooled austenite isothermal decomposition, an increase in the hardness of the transformation products is observed with a decrease in the holding temperature from 246 HV (at 700 °C) to 689 HV (at 250 °C). However, at a temperature of 500 °C, a slight drop in hardness occurs, which is apparently caused by the appearance of retained austenite during the development of bainitic transformation.

Semisolid 357 Al alloy slurry was prepared in the presence and absence of electromagnetic stirring (EMS) and rheo-diecast with various injection velocities, the microstructure, porosity and mechanical properties of the 357 rheo-diecast (RDC) samples were quantitatively analysed as well as their relationships were explored. The results show that injection velocity had greater influence than EMS on the rheo-diecasting process. Injection velocity and EMS had minor influences on the secondary particles but marked influences on the primary particles. For primary particles, increasing injection velocity led to a decrease in particle diameter and an increase in shape factor. EMS can reduce the size and improve the shape factor of primary particles and large pores. The injection velocity was 0.53 m·s−1 at which the optimal values of the porosity and the shape-diameter ratio of the maximum pore for 357 RDC samples, i.e. 0.37% and 1.43 μm−1, can be obtained in the presence of EMS, corresponding to the highest tensile strength and elongation of 274 MPa and 4.85%. The tensile properties were correlated linearly with shape-diameter ratio. It was also suggested that the mechanical properties were enhanced by EMS on account of the reduction of porosity and increase in shape-diameter ratio.

In the present work, the microstructure and mechanical properties of microwave welded Al6061-6%Graphite-SiC hybrid metal matrix composites (MMC) were investigated. The microwave welding was carried out using the principle of microwave hybrid heating and Al6061 powder as an interfacial material. The domestic microwave oven having the frequency of 2.45 GHz and 900 W power was used for the experiments. The charcoal powder as a susceptor was used during the welding process. The hybrid MMCs Al6061-6%Gr-SiC were developed through stir casting process with different weight percentage of SiC keeping graphite constant. The joints were characterized using x-ray diffraction, scanning electron microscope (SEM) equipped with energy-dispersive spectrum (EDS), Rockwell hardness tester and universal testing machine. The x-ray diffraction analysis showed the presence of harder aluminum carbide and aluminum oxide phases. The microstructural study revealed the good metallurgical bonding between the interfacial composites with absence of cracks. The elemental analysis of joint revealed the presence of aluminum, carbon and oxygen with other elements. The average ultimate tensile strength of the microwave joints was recorded as 135 MPa with 4.3% elongation. The average Rockwell hardness at the weld joint observed was 61.5 ± 5 HRB. The evaluation of mechanical properties of microwave welded composites indicated the increase in the tensile strength and hardness as the content of SiC reinforcement increased. The joint strength found to be 65.15% of parent composite, which is similar to the joint strength of welded aluminum-based composites by various techniques such as friction stir welding, laser beam welding, electron beam welding, etc. The present investigation has showed that the microwave energy can be used successfully, as an alternative method to weld the composites.

In this research, the effect of annealing heat treatment on microstructure, mechanical properties and wear behavior of an Al–Zn–Mg/3 wt.% Al2O3 composite that was previously thermomechanically processed (TMPed) in its semisolid temperature range was investigated. The annealing treatment was conducted at 400 ˚C for 15, 30, 45 and 60 min, respectively. The results revealed that this treatment led to the better distribution of alumina reinforcement particles. Also, it was proved that no substantial grain growth occurred which shows the grain size stability of the TMPed composite. In addition, owing to the better distribution of reinforcements, the microhardness values of the composites improved while the compressive strength did not increase noticeably. The wear test results revealed that the wear mode in the non-annealed sample was adhesive whereas in the annealed sample, the abrasive wear was dominant.

In this paper, the lamellar orientation control and mechanical properties of directionally solidified (DS) Ti-49Al (at%) alloy in oxide ceramic crucible were investigated. Based on the nucleation undercooling theory, the feasible solidification parameters for the lamellar orientation control of Ti-49Al (at%) alloy by the seeding technology were selected. The optimal solidification parameters were as follows: the growth rate (V) ranged from 10 to 25 μm/s, and temperature gradient (G) ranged from 10 to 20 K/mm. DS Ti-49Al (at%) alloy with paralleled lamellar orientation was successfully prepared according to the predication solidification parameters. The mechanical properties of DS Ti-49Al (at%) varied with the orientation of the lamellar structures. The specimen with paralleled lamellar orientation showed relatively higher tensile strength (450 MPa) and elongation (0.60%). The mechanical properties of specimens with paralleled lamellar orientation were greater than the specimens with equiaxed grain structures even though the specimens contaminated slightly by the interfacial reaction between the TiAl melt and the oxide ceramics crucible. Meanwhile, the fracture modes of DS Ti-49Al (at%) alloy were interlamellar mode, translamellar mode, or combined with the two modes, which also depended on the lamellar orientations.

Change is constant, as nothing stays the same. Consider the words of the Chinese philosopher Lao Tzu, “Life is a series of natural and spontaneous changes. Don't resist them—that only creates sorrow. Let reality be reality. Let things flow naturally forward in whatever way they like.” Some changes are the result of biology and the passage of time, within the natural cycle or order of things. Others are self-generated, under our own control and resulting from willful efforts, or dependent upon encounters with significant others—family, friends, colleagues, and others close to us. Still, other changes occur because of circumstance or fate, a proverbial "date with destiny" and often beyond what we feel is our control. Whether it is our personal life or occupational, like metalcasting, this change can facilitate transition and transformation. I have coined the term metalmorphasis and this lecture as reflection of how to embrace change, recognize the opportunities presented and utilize it as a vehicle for new beginnings. This is not just philosophical but also a look how we as metallurgist and metalcasters apply and control input variables (time, temperature, pressure, chemical reactions, etc.) to transform metals and create metalmorphasis.

The effect of Eu (Europium) element on eutectic Si in Al–7Si alloys was studied by scanning electron microscopy (SEM), thermal analysis, electron backscattering diffraction (EBSD), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) to elucidate modification mechanism of Eu on eutectic Si. The results indicate that the addition of Eu changes the morphology of eutectic Si from coarse plate-like to fine fibrous. With the increase in Eu content, the number of eutectic cells gradually decreased and the size of eutectic cells increased. Meanwhile, the eutectic nucleation temperature (TN) and the minimum temperature (TMin) decreased, which is caused by the poisoning of AlP particles by Eu. The segregation of phosphorus was found at the center of coarse Al2Si2Eu particle, and the "phosphorus layer" was found at the boundary between the Al2Si2Eu particle and matrix. The length direction of plate-like eutectic Si was , and its outer surface was {111} plane. Few parallel twins were observed in unmodified plate-like eutectic Si. However, the growth of Eu-modified fibrous eutectic Si was isotropous. Multiply twins were often observed in fibrous eutectic Si after modification. The adsorption of Eu was observed along the Si growth direction of eutectic Si and at the intersection of two {111}Si twins, verifying the existence of the poisoning of the TPRE mechanism and IIT mechanism.

This study experimentally investigates the influence of adding SiC on microstructure and mechanical properties of the aluminium alloys welded joints. The SiC particles have been directly added into a zone of friction stir welding (FSW) to make (AA6061–AA2024) SiC composites material. Results show that the effect of adding SiC particles on microstructure refines the grain size in the stir zone by preventing its growth during FSW process. The adding of SiC particles has a significant effect on the thermomechanical zone resulting from restricting the growth of grains. Results indicated that the microhardness of FSW joints is increased from 44 to 86 HV by adding 9.2% SiC particles as compared to that obtained without including SiC under the same welding conditions. It has been observed that the tensile strength is enhanced when the amount of SiC particles are increased by up to 6.9%.

A novel alternating-frequency ultrasonic melt treatment (AUMT) technology is used to refine the grain and improve the strength of AS41 magnesium alloy. The AUMT exhibits better grain refinement efficiency than the traditional 20 kHz single-frequency ultrasonic melt treatment method, showing the grain refinement efficiency up to 82.7%. The improvement of cavitation is suspected to be the reason for better grain refinement. The faster alternating time is beneficial to improve grain refinement efficiency. The AUMT also refines the Mg17Al12 and eliminates the agglomeration of Mg2Si. Such microstructure evolution helps improve the tensile strength and elongation of AS41.

Modern products and structures require efficient material joining processes for their construction, able to combine similar or dissimilar materials, which almost always includes high-performance polymers. To design such joints, it is necessary to first understand the techniques currently used in this technological field and how they can be improved using advanced technological joining processes. In this manuscript, a review of several polymer-joining techniques is made, highlighting the recent technological advances in this field. The search for improved mechanical performance and lower costs has led to the development of new, high-performance engineering polymers, which require highly specific joining processes. These can include adhesive bonding, mechanical joining, welding or a combination of different processes, a technique known as hybrid joining. Several experimental works available in the literature have proven the validity of these techniques, although optimization processes are necessary to attain maximum performance. Additionally, extensive numerical with different methods and models has been carried out to better understand the processes and support parametric analysis. The intent of this work is to review studies on the most important polymer bonding techniques, the numerical models applied to simulate these techniques, the use of hybrid joints and describe promising techniques that are being developed and proposed for future use.

The present study was carried out to investigate the effects of Ni and Zr additions, individually or in combination, on the room-temperature tensile properties of 354 casting alloy (Al–9wt%Si–1.8wt%Cu–0.5wt%Mg) which was isothermally treated at temperatures in the range of 155–350 °C and aging times up to 1000 h. Tensile tests were carried out in the as-cast, solution heat-treated, and aged conditions using different aging times up to 1000 h. Quality charts were used as an evaluation tool for selecting the optimum conditions to achieve superior tensile properties and optimum quality in 354-type alloys. Zirconium reacts only with Ti, Si, and Al to form (Al,Si)2(Zr,Ti), (Al,Si)3(Zr,Ti), and Al3Zr phases. The beneficial effects of Zr and Ti additions appear in the refining of the α-Al grain size which reduces the size of the Al2Cu and α-Fe particles. Tensile test results at ambient temperature show a slight increase in alloys with Zr and Zr/Ni additions, particularly at aging temperatures above 240 oC. It is suggested that the maximum obtainable quality index values by means of heat treatment are the difference between the quality index values for the as-cast and solution heat treatment conditions.

Active vision sensing is widely used in intelligent robotic welding for bead detection and tracking. Disturbed by welding noise such as arc light and spatter, it is a hard work to extract the laser stripe and feature values. This paper presents a method for denoising and feature extraction of weld seam profiles with strong welding noise in gas metal arc welding (GMAW) process by using stacked denoising autoencoder (SDAE). This algorithm encodes the images of various butt joints with strong welding noise to several useful intermediate representations, which can be decoded to the image of pure laser stripe in 1-pixel width. The results show little deviations when there are large spatters across the laser stripe. A back propagation neural network (BPNN) is developed to verify the reliability of the intermediate representations gotten from the encoder, in which the intermediate representations are input neurons and the weld seam width is output neuron. The average width error in training dataset and testing dataset is 0.042 mm and 0.061 mm. The results show that this algorithm can extract the weld seam profiles with strong welding noise and extract feature values accurately.

High-energy density beam processes for welding, including laser beam welding and electron beam welding, are essential processes in many industries and provide unique characteristics that are not available with other processes used for welding. More recently, these high-energy density beams have been used to great advantage for additive manufacturing. This review of the literature serves to provide an overview of the evolution of the laser and electron beam processes including the fundamental nature of the beam itself and how such a high-energy density beam has been applied for welding. The unique nature of each process regarding weld bead formation and penetration, and metallurgical considerations are covered in detail. In addition, the evolution of monitoring systems for both characterization and control of these beam processes is reviewed. Over 500 references have been cited in this comprehensive review that will allow the reader to both understand the current state-of-the-art and explore in more detail the fundamental concepts and practical applications of these processes.

This research studied the electrochemical corrosion behavior in 1 M hydrochloric acid of a Fe-Cr-Mo-B-C alloy fabricated using spark plasma sintering of an amorphous alloy starting powder. The corrosion performance was evaluated using electrochemical impedance spectroscopy and potentiodynamic polarization tests and was benchmarked with conventional materials: 316L stainless steel and 1080 carbon steel. The corrosion reaction products on the surface were characterized using X-ray photoelectron spectroscopy, scanning electron microscopy and energy-dispersive spectroscopy. The specimen sintered at 800 °C had approximately 94% densification, whereas the specimen sintered at 900 °C exhibited greater densification of approximately 98%. The sintered specimens consisted of nanocrystalline (Fe,Cr)23C6 and (Cr,Fe)2B particles embedded in a body-centered-cubic Fe-based matrix. These sintered specimens exhibited better corrosion resistance than conventional alloys. When the density of the sintered alloy decreased from 98 to 94%, resistance to chloride attack was increased because of the formation of a thicker and more uniform surface product as well as a chromium-containing oxide layer.

The joining of the SiCf/SiBCN composite was difficult due to the undue reactions between the SiCf/SiBCN composite and the common Ni- or Co-based filler alloy. In this paper, a new filler alloy with the nominal composition of Co-20Ni-12Pd-18Nb-15Cr (wt.%) was newly designed to join the SiCf/SiBCN composite. Compared with the BNi-5 filler alloy, the periodic banded structure in the reaction layer was eliminated. During the brazing process, the element Cr played an active role in the interfacial reactions and formed Cr23C6 layer at the surface of the SiCf/SiBCN composite. The interfacial reaction layer could inhabit the diffusion of the elements Co and Ni to the SiCf/SiBCN substrate. And then the interfacial reactions were controlled well. Under the brazing condition of 1200 °C/10 min, the average joint strength was increased from 18.2 to 54.9 MPa.

Cu–6.5% Al alloys and Cu–6.5% Al alloys containing small amounts of silicon (Si) and manganese (Mn) were deposited using wire arc additive manufacturing (WAAM) by feeding two different components of wires simultaneously into the molten pool. The deposited alloys were homogenized by heat treatments at 800 °C (2 h). The effect of addition of Si and Mn on the microstructure and mechanical properties of Cu–6.5% Al alloys were investigated. Microstructural and formation of intermetallic compounds were studied. Results revealed that upon heat treatment, Si and Mn were able to restrain the dislocation movement due to the formation of second-phase particles. When compared to Cu–Al alloys, mechanical testing of the Cu–6.5% Al alloys having Si and Mn showed that hardness had increased by120 Hv, ultimate tensile strength (UTS) had increased by 284 MPa and yield strength (YS) had increased by 365 MPa, whereas its elongation (EL) had decreased by 22%.

The grain growth mode of titanium alloys remains controversial. In this study, ANSYS and cellular automaton-finite difference code μMatIC were coupled to simulate the multi-scale solidification process of commercial purity titanium and two types of titanium alloys with different solute concentrations. Investment casting of Ti–6Al–4V was carried out in counter-gravity casting method in vacuum environment. Results showed that the grain growth mode of titanium alloys depended on the solute compositions. Grain growth mode of titanium alloys transfers from planar to dendritic with the increased solute. The grain growth morphology of Ti–6Al–4V alloy presents cellular dendritic due to slight solute segregation in the solidification. The predicted grain structure was validated by comparison with the microstructural observation results. Both the prediction and experimental results revealed that equiaxed grains were obtained in investment casting of Ti–6Al–4V regardless of the thickness. The grain size increased with the wall thickness of the cast part.

The influence of Si additions (0.1, 0.3, 0.6, 1 wt%) on microstructure, hardness and elevated-temperature sliding wear behavior of AX53 magnesium alloy (Mg—5 wt% Al—3wt% Ca) has been investigated by performing a ball-on-disk high-temperature wear test at different temperatures (RT, 100, 150, 200 °C). The results clearly show that without Si addition, the microstructure of the as-cast AX53 alloy consists of dendritic primary α-Mg phase and lamellar eutectic structure consists of layers of α-Mg and (Mg, Al)2Ca lamellar intermetallic compounds that alternate together. With Si additions, a new intermetallic compound rich in Si can be defined as MgCaSi of a granular, needle and bulky morphologies with different sizes forms within the inter-dendritic regions of α-Mg. Formation of fine granular MgCaSi intermetallic compounds as well-distributed particles is associated with the addition of 0.6 wt% Si. The alloy containing 0.6 wt% Si shows the highest hardness value and the best wear resistance at all temperatures of the wear test. In the Si-containing alloys, weight loss increases with increasing the temperature of wear test compared to the RT wear test regardless of the Si content. However, the Si-containing alloys have lower weight loss than the investigated alloy without Si addition. The wear mechanisms have been also discussed.

The possibility of raising the impact toughness of medium-manganese TRIP-steel Fe – 0.2% C – 6% Mn – 3% Al by application of a novel heat treatment involving quenching from the intercritical temperature range and subsequent tempering is investigated. Electron microscope and x-ray diffraction studies are performed after the heat treatment. The quenching mode providing the highest impact toughness is determined.

The surface layer obtained by ion-beam stirring of a thin carbon film deposited on titanium alloy VT6 is studied. The composition and the chemical condition of elements in the surface layer are determined. Formation of a disordered carbon structure in a thin surface layer (20 – 40 nm) and of titanium carbides in the transition layer is detected. A model of formation of structure in the specimens during irradiation is developed. It is shown that formation of a disordered carbon structure, of titanium carbides, and of dislocation substructures is responsible for elevation of the microhardness of the specimens after ion-beam stirring.

The influence of the initial structure on formation of austenite, evolution of structure, and elevation of operating characteristics of steel SA508 Gr.3 (0.24% C, 1.40% Mn, 0.88% Ni, 0.54% Mo) after an intercritical heat treatment (IHT) is studied. After the IHT, the grain size of the hypoeutectoid ferrite in the steel with an initially ferritic-bainitic structure is much larger than in the initially bainitic or martensitic structures. The density of the low-angle and high-angle boundaries is much higher in the steel with initial bainitic or martensitic microstructure. The initial microstructure affects substantially the strength and the impact toughness of the steel subjected to IHT. The mechanical properties are increased as a result of refinement of the microstructure and growth of the density of grain boundaries.

Samples of titanium alloy VT6 obtained by the method of cold gas dynamic spraying (CGDS) and subjected to hot isostatic pressing (HIP) for lowering the porosity and improving the mechanical properties are studied. The HIP is conducted at a temperature of 900°C and a pressure of 110 MPa. This reduces the volume fraction of pores from 8 to 0.5% and raises the ultimate strength of the samples from 70 to 950 MPa and the elongation by 12%.

Friction stir welding (FSW) is a relatively new welding technology. Although FSW technology has been widely used in many industries, there is a lack of effective online detection method of process parameters. Weld temperature and tool positioning are two key parameters in the study of process parameters. To realize online measurement of weld temperature and tool positioning in FSW, a measurement method of weld temperature and tool positioning is proposed by designing a new online detection device in FSW. The weld temperature measurement is realized by the material emissivity model based on the principle of infrared temperature measurement. Based on the principle of trigonometric distance measurement, the tool positioning is measured by data processing algorithm. In order to verify the feasibility of the measurement method, the welding processes of aluminum alloy with two thicknesses are detected online. The results show that the weld temperature measurement accuracy of the online detection device is within ± 2%. The measurement of tool positioning is realized. This measurement method proposed in this paper can be applied to the optimization of process design and temperature feedback control.

The formations and fracture behavior of the AA2A14-T6 aluminum alloy friction stir welded (FSWed) joints are investigated under different ratios of rotational speed to welding speed (n/v). The relationship between the viscous layer (δ) and the rheological layer (ξ) is the key factor to determine the welding quality of joints. When δ

Friction stir welding (FSW) is a solid-phase welding method. Weld forming and welding quality are related to the heat generated by plastic flow in FSW process. Therefore, it is of great significance to realize the measurement of the viscoplastic heat generated in FSW process. In this paper, based on the working principle of rotary viscometer, the calculation model for the viscoplastic heat in friction stir welding was proposed. The validity of the calculation model was verified by simulation experiment. The correctness of the calculation model was verified by friction stir welding experiment.

The composition profile and the microstructure formation of unidirectionally solidified Al–4.5 wt% Cu sample was investigated. The thermal analysis technique determined the vertical Bridgman’s test sample solidification parameters. Characterization of microstructures was conducted with an optical microscope, and Image-J software determined the α-Al area. Energy-dispersive X-ray spectroscopy was used to assess the composition. The composition profile was confirmed with the actual density and micro-hardness value. The results show that the composition of Cu varies between 4.93 and 3.99%, along with the 98.3% drop in the cooling rate. The reduction of Cu composition is in line with the α-Al area, actual density, and micro-hardness value. Two different morphologies of eutectics are found, fine internal fragments in 1.12 to 2.4 °C/s (less than 35 mm) and the lamellar in 0.04 to 0.06 °C/s cooling zone (more than 35 mm).

Dissimilar metal welds (DMWs) made between ferritic steels and austenitic alloys are used extensively in high-temperature power plant components. These DMWs experience premature creep failure in the ferritic steel’s heat affected zone (HAZ), close to the weld interface. Steep variations in microstructure and chemical composition across the dissimilar weld interface have been the contributing factors for the failure. Graded transition joints (GTJs), developed by functionally grading the chemical composition in layers, have been proposed as potential candidates to replace DMWs. In this research, GTJ coupons were fabricated between 2.25Cr-1Mo steel and Alloy 800H base material using two filler materials: (i) Inconel 82 and (ii) P87. These samples were aged at 600°C for 2000h to accelerate high-temperature microstructural evolution seen in service conditions, before subjecting them to short-term (~1 month) creep tests. Surface strains were measured using digital image correlation (DIC) technique to extract creep strain rates at different locations within GTJs. Both the GTJs exhibited heterogeneous creep strain distribution. Creep strain accumulated in the FGHAZ of 2.25Cr-1Mo steel, similar to type IV failure associated with Cr-Mo steel weldments. Microstructure based creep model framework was developed to describe the discrete creep strain rates observed in various 2.25Cr-1Mo steel regions of GTJs.

The optimization of welding parameters of the welded joints of TC4 titanium alloys/304 stainless steel (TC4/304 SS) by friction stir lap welding (FSLW) based on orthogonal test was researched. The results show that under low heat input (low rotating speed and high traversing speed), there was a damaging defect in stir zone (SZ) and cracks started from the defect under the tension. Under high heat input (high rotating speed and low traversing speed), the intermetallic compounds were barely formed, and the cracks formed from 304 SS blocks existed in thermal mechanically affected zone of TC4 titanium alloys (TMAZTC4), eventually obtaining the highest fracturing load. However, under middle heat input (middle rotating speed and low traversing speed), the intermetallic compounds and the maximum hardness were found at the interface, and cracks started from these compounds under the tension, getting a middle fracture load. In conclusion, the joints with good properties can be obtained with high rotating speed and low traversing speed.

The process input data which materials processing operations can collect for each unit of production is extensive. Large datasets have long been difficult to work with as computing power to execute analysis in a timely fashion was unavailable. Further, the great velocity at which the data is generated makes near real-time decision-making unwieldy without a new set of tools with which to do the work. When troubleshooting by a small dataset, such as the last few hours of production, observations made on the measured parameters can be misleading. Machine learning is opening doors to high-dimensional data analysis in material processing. In this work, high-pressure die-casting (HPDC) is explored as an exemplar of high-volume materials processing. HPDC process summary data from a full year of production data covering over 950,000 machine cycles is analyzed via supervised machine learning methods to successfully model the prediction of good parts and process scrap as determined by the die-casting machine. Additionally, the prediction of ultimate tensile strength via a classification method of extracted tensile bars is performed and the important features identified are discussed. Supervised learning is found to be a useful tool for materials processing applications.

Transient liquid phase (TLP) bonding of Ti-6Al-4V/IN718 dissimilar joint was investigated using Cu interlayer at 950 °C for 5–45 min. The microstructure of the bonding zone was studied by using optical and scanning electron microscopes, energy dispersive spectroscopy, and X-ray diffraction analysis. Shear and microhardness tests were also used to evaluate the mechanical properties of the TLP joints. The results indicated that α-Ti, Ti2Cu, and Ti2Ni phases were formed in the athermally solidified zone of the joints. A Widmanstatten structure consisting of eutectoid mixture of α-Ti and Ti2Cu was formed in the diffusion affected zone of Ti-6Al-4V side, and the formation of β(Nb) and NiTi eutectic and Cr2Ti, FeTi, Ni3Nb, Fe5Nb3, and Cu0.035 Ni0.565Ti0.4 intermetallic compounds was predicted in the diffusion affected zone of IN718 side. The hardness values decreased in different bonding zones with extending the bonding time, while an inverse trend was observed in the athermally solidified zone. The maximum shear strength of 367 MPa was obtained. The morphology of the fracture surfaces of shear samples was investigated.

Additive Manufacturing is enabling the casting of complex geometries directly from digital design data, including 3D-scanned and reverse-engineered structures and even functionally graded lattices. By ink jetting binder into a bed of sand layer-by-layer, dimensionally precise sand molds and cores can be printed to serve as soft tooling for sand casting. However, the related increase in geometry complexity can lead to challenges in ensuring casting quality and yield. One recently explored remedy is to introduce sensors (the Internet of Things) to enable the collection of a diversity of data at difficult-to-access locations in molds in order to measure temperature, pressure, moisture, and core shift. This effort has explored measuring barometric pressure at strategic locations to evaluate the ventilation design of internal cores. Optimized and measurable ventilation can be leveraged to improve the quality of castings by reducing porosity and improving surface finish. By measuring the pressures that accumulate within cores due to binder decomposition, new ventilation designs and strategies—enabled with complex, 3D printed fluidic channels—can be explored. In this work, two castings with different metal temperatures were poured and internal pressures were measured and compared to simulations demonstrating that wireless disposable sensors can be used to measure pressure and that the measured pressure correlated with venting strategies now possible with 3D printed sand cores.

The morphology of the weld seam, the formation mechanism of interface, and the microstructure and mechanical properties of both direct and AlSi12 (ER4047)-added dissimilar 5A06Al/Ti6Al4V lap joints were investigated, respectively. The Gibbs free energies of intermetallic compounds, such as TiAl3, TiAl, and Ti3Al, were calculated. The results showed that the interface layers were mainly composed of Ti3Al, TiAl, and TiAl3, and the order of them was TiAl3, TiAl, and Ti3Al from outside to inside. The addition of ER4047 interlayer could suppress the formation of IMCs and reduce the micro-cracks in TiAl3 layer. The ER4047-added joints featured good mechanical properties, i.e., the shear strength of 2087 N, 2405 N, and 2157 N respectively, which were much higher than the shear strength of 1721 N for the direct joint. Furthermore, the fracture model of the direct joint was brittle fracture, while that of the ER4047-added joints was quasi-cleavage. The results can provide theoretical guidance for the prediction of Ti/Al interface reaction and welding of other dissimilar metals.

Carbon steels can be sensitive to solidification cracking. Predicting their susceptibility to solidification cracking can save cost and time compared to testing, and it can be very useful for designing new steels or welds. Crack susceptibility predictions were made for carbon steels using the recently proposed simple susceptibility index for cracking during solidification, maximum │dT/d(fS)1/2│ near the end of solidification (T temperature and fs fraction solid). T vs. (fS)1/2 curves of the carbon steels were calculated by three different solidification models: equilibrium, Scheil, and Scheil with back diffusion of the available commercial thermodynamic software. The crack susceptibility predictions based on these solidification models were compared to various crack susceptibility test results of carbon steels, and the predictions based on Scheil with back diffusion were found consistent with the most of the crack susceptibility test results. Solidification temperature ranges of the carbon steels, determined based on the solidification models of equilibrium, Scheil, and Scheil with back diffusion, were used to explain the crack susceptibility predictions. The role of the alloying elements of the carbon steels in solidification cracking susceptibility was discussed.