Transactions of The Indian Institute of Metals最新文献

This research aims to examine the impact of carbon nanotubes (CNTs) agglomeration on the microstructure, mechanical properties, and wear behavior of the FeCoNiMn medium entropy alloy. The CNTs were included into the mixture at weight percentages of 1, 1.5, and 2 using mechanical alloying (MA) and spark plasma sintering (SPS). The base alloy displayed brittle characteristics with a compressive strength of 880 MPa and a hardness of 400 HV. The composite containing 2 wt.% CNTs had the lowest hardness (280 HV) and compressive strength (400 MPa). The wear test demonstrated that the presence of agglomerated CNTs led to an increase in weight loss. The base alloy showed signs of adhesive wear on its worn surface, but the composite samples displayed delamination-like wear characteristics. The findings point to an unanticipated decrease in wear resistance and deterioration of mechanical properties brought on by CNT aggregation.

For the first time, CuAlVMg high-temperature shape memory alloy (HTSMA) with unprecedented alloy composition and with extended solubility of vanadium element was fabricated as-cast ingot by arc melting method, then homogenization of the alloy in high β-phase temperature region and quenching in iced-brine water were performed, respectively. The characteristic forward martensite to austenite martensitic transformation (MT) temperatures were detected at around 390 °C, which put the novel alloy in the category of HTSMAs. The thermal response of the alloy at high-temperatures was observed by DTA test as coherent with usual Cu-based HTSMAs. The residual sub-eutectoid precipitations emerging at around 500 °C hindered the direct martensitic transformation. The martensite structure of the alloy was revealed by XRD, SEM and optical microscopy tests.

Cold spraying methods are used to prepare Cu/Ni composite coating on Q235 substrates. The porosity, micromorphology, and microhardness and corrosion properties of the copper coating prepared by cold spraying are studied. This experiment mainly explores the microstructure and corrosion resistance of Cu/Ni composite coatings prepared by different composition powder ratios. The heat treatment process of the coating was carried out to explore the effect of the heat treatment process on the microstructure and corrosion resistance of the coating. The results indicated that the porosity of the coating increases slightly with an increase in nickel powder content. The metal nickel plays an anodic protection role in the Cu/Ni battery. However, too much nickel will lead to too much anode material, and the overall structure of the coating will be destroyed after anode corrosion. The composite coating prepared with 40 wt% nickel powder has the best corrosion resistance. After heat treatment, the corrosion resistance of copper/nickel composite coatings is reduced, and the quality of the coatings is improved.

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The current study centers on two techniques: neural network (NN) and response surface methodology (RSM), applied to predict the final density (FD) of sintered aluminum preforms. In this work, the load, the aspect ratio and the initial preform density were taken as input parameters and the response (output) variable measured was FD. Prediction for the response variable FD was obtained with the help of empirical relation between the response and the input variables using RSM’s (RSM) Box–Behnken design of experimental technique and also through Neural Network (NN). Predicted values of the response by both the techniques, i.e., RSM and NN were compared with the experimental values and their closeness with the experimental values was determined. Moreover, it has been discovered that the aspect ratio has minimal impact on densification and that the FD of the preform rises with both the load applied and the initial preform density of the sintered preforms. The authors were able to predict the FD of sintered preforms of Al–TiB₂ for different initial preform and aspect ratio conditions by using NN and RSM techniques.

We have used CALPHAD-guided design methodology to develop a novel lightweight Al–Ti–Hf alloy with nearly 50 vol% in-situ formed trialuminide reinforcement. Through compositional optimization, Al_87.5Ti_6.25Hf_6.25 (at%) was chosen as the experimental alloy composition. Using the Differential scanning calorimetry (DSC) and CALPHAD-derived melting point data, the as-cast alloy was subjected to 24 h homogenization heat treatment at 475 °C to achieve equilibrium. X-ray diffraction (XRD), Scanning electron microscopy (SEM), and DSC analyses revealed that the developed alloy has a dual-phase microstructure, composed of approximately 50 vol% of an FCC Al-rich matrix and 50 vol% of an Al₃(Ti, Hf)-type (D0₂₂) phase, which matches closely with the thermodynamic calculations. The experimental onset melting point of the Al-rich matrix was determined to be 638 °C which is significantly higher than Al–Si-based high-temperature (HT) alloys, indicating the potential of the developed alloy as a HT structural material. Nanoindentation (NI) tests demonstrated the remarkable phase-specific nanomechanical properties of the alloy. The developed alloy possessed a microhardness of 3075 MPa, which not only surpasses 7075-Al, A390-Al alloys and CP-Ti, but also rivals the microhardness of Ti–6Al–4V alloy at nearly 18% lower density. The study highlights the potential of this novel alloy in applications that demand for materials with low density, high hardness, and superior wear resistance.

Graphical Abstract

Direct metal laser sintering (DMLS) is one of the well-known 3D printing processes for the preparation of functional prototypes. One of the limitations of DMLS is the reusability/ recyclability of the process consumables (waste metallic powder). In the past, some studies testified to the reusability of waste metallic powder of DMLS to support a circular economy. But hitherto little has been reported on investigations of recycled DMLS powder collected in mixed form (comprising more than one metallic alloy). This study highlights the investigations performed on mixed bio-compatible metallic powder (90% of 17–4 precipitate hardened stainless steel and 10% of Ti-6Al-4 V) collected (as waste) from the institute laboratory. During the pilot run, the samples were 3D printed on DMLS at different energy densities (ED) (66.66, 71.42, 90.67 J/mm³) selected based on the combination of available input parameters (i.e., laser power (LP), scanning speed (SCS), hatch distance (HD), layer thickness (LT), etc.), but all samples failed while printing. For successful 3D printing, the collected waste powder was preprocessed for thermal treatment (leading to chemical decomposition) at two different temperatures (550 °C (below recrystallization temperature) and 800 °C (above recrystallization temperature)). The preprocessed mixed powder at 550 °C was successfully 3D printed with ED 71.42 J/mm³ (attained with LP 120W, SCS 800 mm/s, HD 70 µm, LT 30 µm). The printed samples resulted in Young’s modulus (E) of 4155 MPa (in tensile) and 211 MPa (in flexural) along with a surface hardness of 335.9 HV at 50N. The in vitro studies outlined a corrosion rate of 0.000411 mm/year for a mixed powder-based functional prototype. Also, the specific wear rate was observed as 0.000036mm³/NM. The outcomes are also braced by scanning electron microscopy and energy dispersive spectroscopy (EDS) analysis.

In this study, the influence of the number of roll passes in hot rolling process to microstructural and mechanical properties of medium-carbon steel within applying the same amount of total deformation was investigated under as-rolled and quenched and tempered conditions. Tensile strengths of as-rolled specimens were increased depending on the higher volume percentage of martensite at lower roll passes. The size and distribution of martensite/austenite formations directly contribute to toughness rather than tensile strength, and the coarser martensite/austenite islands give rise to differences between actual and software predicted tensile strengths. It was revealed that fracture surfaces of as-rolled specimens were influenced by the rolling pass number changes. Spherical chromium (Cr) and molybdenum (Mo)-rich precipitates were formed more intensively in samples produced with 4 roll passes compared to 5 and 6 roll passes. Finer carbide formations and smaller dimples were found in heat-treated specimens compared to as-rolled ones. Furthermore, the positive contribution of initial martensite microstructure to mechanical properties was observed in heat-treated specimens.

Dissimilar Ti/Al butt-lap joints were fabricated via ultrasonic-assisted friction stir welding, and the material flow was enhanced due to the acoustoplastic effect, inhibiting the formation of welding defects. Ultrasonic vibration refined the microstructures and accelerated the dynamic recrystallization in the nugget zone. Consequently, 10–15% decrease in the average grain diameter and 20% increase in the fraction of high angle grain boundaries were obtained. The intermetallic compounds layer of TiAl₃ generated along the butt-line, while the atomic diffusion layer formed along the lap-line. With the help of ultrasonic activation, the atomic diffusion layer got thickened (from 1.6 to 2.3 μm), improving the peak load/elongation of joint from 1.2 KN/3% to 2.1 KN/6%. Furthermore, the novel double-ultrasonic-sources were utilized, and the joint made by this method exhibited a more satisfactory welding performance; the average grain size of nugget zone decreased to 5 μm, and the peak load/elongation of joint increased to 2.6 KN/8%.

In DED melt pools, high solidification rates and temperature gradients complicate characterizing competitive dendrite growth. To address this, the WBM phase-field method simulates dendrite growth in the RCF103 alloy, revealing correlations between tilted dendrites and solidification parameters. It explores the competitive mechanism between different dendrite morphologies (columnar and seaweed) and the role of surface energy anisotropy and tip undercooling in determining dendrite shape. These findings enhance our understanding of DED melt pool dendrite growth, facilitating the establishment of a relationship between solidification structure, conditions, and process parameters.

The aim of this study is to assess the fatigue load-carrying characteristics of Ti–5Al–2.5Sn alloy reinforced with tungsten particles and determine its appropriateness for aerospace and other commercial uses. Ti–5Al–2.5Sn composite samples were produced using five distinct weight percentages of tungsten particles (0.5%, 1.0%, 1.5%, 2.0%, and 2.5%) reinforcement through the microwave sintering technique. Five ASTM standard test samples were subjected to fatigue tests along with field emission scanning electron microscope (FE-SEM) analysis to examine the impact of tungsten reinforcement in a titanium alloy matrix. Analysis of crack propagation and failure study was conducted using finite element analysis (FEA) software. The experiment and FEA simulation results indicate that 0.5 wt% of tungsten-reinforced matrix (Ti–5Al–2.5Sn) composites show significant improvement in fatigue performance. Crack initiation begins in the matrix region due to cyclic stress, and the particle-breaking mechanism occurs under heavy loading conditions and was examined using FE-SEM. The results revealed that Ti–3Al–2.5Sn–2W composites acquire experimental fatigue strength of 384 MPa and 406 MPa which is 3.92% and 1% higher than that of the Ti–5Al–2.5Sn matrix. However, the finite element fatigue strength of 398 MPa and 412 MPa are 4.87% and 1% higher than that of the Ti–5Al–2.5Sn matrix.