This study investigates the correlation between microstructural evolution and the enhanced corrosion behavior of an innovative Ti–5Cu–1Si alloy, processed via laser powder bed fusion (L–PBF) under a systematic range of volumetric energy densities (VED), encompassing 43.98, 61.68, and 77.55 J/mm³. To decouple the synergistic effects of Cu and Si alloying elements and VED, Ti-5Cu-1Si and pure Ti were further printed at a consistent VED of 43.98 J/mm³. Incorporating Cu and Si into pure Ti induced a grain morphology shift from columnar prior β to equiaxed β grain morphology. Elevating the VED beyond 43.98 J/mm³ promoted a dense population of equiaxed prior β grains, reducing the average grain size from 4.723 µm to 1.922 µm and markedly improving grain size uniformity. On the other hand, increasing VED from 43.98 to 77.55 J/mm³ was accompanied by an increase in the β phase fraction from 22.59 to 37.06% at the expense of a reduction in the α phase fraction from 23.63 to 8.08%. The slower cooling rate associated with the highest VED of 77.55 J/mm³ promoted the diffusion of supersaturated Cu and Si atoms out of the Ti lattice, thereby reducing lattice microstrain from 0.46% to 0.16%. The electrochemical results highlighted that a set of microstructural evolution and enhanced microstructural homogenization induced by elevated VED manifest as a promotion of the corrosion potential ( E corr ) from − 0.26 V to -0.17 V and a concomitantly decline in corrosion current density ( I corr ) from 7.86 µA/cm 2 to 1.43 µA/cm 2 . These microstructural evolutions, coupled with favorable electrochemical responses, were demonstrably associated with an increase in the average passive film resistance ( R p ) on Ti-5Cu-1Si alloy, enhancing from 9.2 KΩ. cm 2 up to 11.53 KΩ. cm 2 .

Over the past two decades, high-entropy alloys (HEAs), also referred to as complex concentrated alloys (CCAs) or multi-principal element alloys (MPEAs), have garnered considerable attention due to their unique structural features and exceptional mechanical performance, including impressive resistance to oxidation, corrosion, and elevated temperatures. Nonetheless, most HEAs developed thus far are based on heavy constituent elements, resulting in high densities that limit their suitability for weight-critical applications. To address this, recent efforts have shifted towards creating lightweight HEAs (LWHEAs) to enhance energy efficiency. Within this category, magnesium-bearing HEAs are especially attractive due to their inherently low densities; however, a comprehensive understanding of these systems remains lacking. This work presents a critical evaluation of advancements in the production and development of LWHEAs, paying particular attention to systems with substantial magnesium additions. It offers a systematic analysis of synthesis methods, design philosophies, microstructural development, mechanical characteristics, and corrosion behavior of Mg-containing HEAs as documented in existing literature. The review concludes by highlighting promising future research avenues and suggesting directions for further exploration in this nascent field.

In the present work, a novel Ti–5Cu–1Si alloy was developed via laser powder bed fusion (L-PBF) using the in-situ alloying approach. The alloy was then subjected to annealing heat treatments at 700, 850, and 1100°C, followed by controlled, slow furnace cooling. Subsequently, the impact of the annealing treatment on the microstructure and corrosion resistance of this alloy was studied. The results demonstrated that annealing of the LPBFed Ti–5Cu–1Si alloy at 700, 850, and 1100 °C temperatures promoted the formation of α-Ti, Ti2Cu, and Ti5Si3 phases, along with a decrease in the compositional disparity between the α phase and the Ti matrix attributable to the depletion of the non-equilibrium acicular α’-Ti phase from the supersaturated Cu and Si elements. When heated at 1100 °C, the average icorr value decreased from 0.86 to 0.33 µA, and the average Ecorr value increased from − 0.223 to − 0.215V. This trend is attributed to the transformation of the non-equilibrium α’ phase into the eutectoid mixture of α-Ti+Ti2Cu+Ti5Si3, reduced lattice microstrain, lesser compositional difference between the α-Ti phase and the Ti matrix, and the increased microstructural homogeneity. Annealing at 850 °C further enhanced the corrosion resistance of the alloy, increasing the average Ecorr value to − 0.141 V and decreasing the average icorr value to 0.1 µA. Annealing at 700 °C resulted in an average Ecorr value almost identical to that of the sample annealed at 850 °C (− 0.165 V), although the average icorr value was 0.32 µA. The attribution lies in the reduced sizes of β grains and the α phase, coupled with more evenly distributed Ti2Cu and Ti5Si3 intermetallic precipitates in the LPBF-produced Ti–5Cu–1Si alloy microstructure after annealing at 700 and 850 °C, relative to those at 1100 °C. In addition, a significant increase in the passive film resistance (Rp) values was observed after annealing at 850 °C, rising from 0.068877 to 70.736 MΩ. cm2. This was related to the protective effect of the Ti2Cu and Ti5Si3 intermetallic phases, which shielded the α’/α-Ti, as well as the presence of smaller, equiaxed prior β grains and reduced spacing between Ti2Cu and Ti5Si3 precipitates. The improved corrosion behavior of the alloy after annealing at 850 °C, compared to other Ti–Cu-based alloys produced by L-PBF and casting processes reported in previous studies, suggests that it could be a suitable candidate for biomedical applications.

Hybrid nanocomposites based on AA2024 reinforced with TiO2 and SiO2 nanoparticles (0–1 vol%) were fabricated using stir casting followed by accumulative roll bonding (ARB) up to five passes. To capture the complex interplay between composition, processing, microstructure, and mechanical response, a machine learning framework integrating random forest regression, Pareto multi-objective optimization, and Weibull statistics was developed. The random forest model accurately predicted yield strength (R2 = 0.97, MAE = 12.3 MPa), indicating that ARB pass number (42%) and grain size (31%) are the dominant controlling features. Pareto optimization identified an optimal untested condition of 0.5 vol% SiO2 and 0.8 vol% TiO2 after four ARB passes, yielding a predicted UTS of ∼472 MPa with an elongation of ∼5.8%. Weibull analysis revealed that the five-pass ARB condition exhibits the highest reliability (Weibull modulus m ≈ 8.2), with a survival probability exceeding 95% for yield strength above 350 MPa. Multivariate analysis using PCA and hierarchical clustering clearly separated cast, annealed, and ARB-processed microstructural states. A clear synergistic effect between reinforcements was observed: at 1.0 vol% TiO2, increasing SiO2 enhances strength, whereas in the absence of TiO2, the same increase reduces strength, confirming the necessity of a hybrid reinforcement strategy.

Effects of grain refinement using an Al–10Ti–5B master alloy on the hot tearing susceptibility of A206 alloy were examined. The results from real-time thermal and load analyses along with subsequent macroscopic and microscopic examinations of the castings were used to evaluate the predictions of three different hot tearing susceptibility models. Thermal analysis showed that grain refinement elevated the liquidus temperature and lowered the solidus temperature of the alloy with no significant impact on its coherency temperature. Davies's criterion suggested that, contrary to the experimental results, grain refinement would decrease hot tearing susceptibility of the alloy. NNC indicated that hot tearing susceptibility was reduced at a small grain refinement addition but increased at higher additions. Load rate criterion indicated that hot tearing susceptibility was increased with increasing grain refinement. Davies's criterion indicated that hot tearing susceptibility was increased at a low grain refinement addition but reduced at higher additions.

This study explores the effect of in-situ alloying and volumetric energy density (VED) on the microstructure of Laser Powder Bed Fusion (L-PBF) fabricated Ti alloys. Pure Ti, Ti-5Cu, and Ti-5Cu-1Si (wt%) samples were printed using elemental powders with varying VEDs. This study investigates the influence of VED and Cu/Si additions on the growth restriction factor (Q) and columnar-to-equiaxed transition of the beta phase. Pure Ti samples exhibited coarse, prior columnar beta grains with an average diameter of 106 mu m, and a grain shape factor greater than 3.0. In contrast, both Ti-Cu and Ti-Cu-Si samples displayed a significant fraction of equiaxed prior beta grains with a near-spherical morphology. Additionally, Cu/Si addition refined the prior beta columnar grains, reducing their average diameter to 37 mu m and 25 mu m in Ti-Cu and Ti-Cu-Si, respectively. Furthermore, the study reveals a strong dependence of microstructure on VED in the Ti-5Cu-1Si alloy. Higher VED promotes a more uniform distribution of solute elements and a lower thermal gradient, resulting in finer equiaxed beta grains with an average diameter of 4.9 mu m, compared to samples printed at lower VEDs. The addition of Cu and Si also significantly refined the lath-like alpha phase and decreased the c/a ratio of the Ti HCP lattice, introducing lattice microstrains in the Ti-Cu and Ti-Cu-Si alloys. These findings demonstrate the potential of in-situ alloying and VED optimization for tailoring microstructures in novel Ti alloys fabricated via L-PBF, paving the way for achieving superior mechanical properties.

Laser cladding is a facile and inexpensive method for coating a layer of duplex stainless steel on steel substrates. In this study, a thick coating (200 µm) of Fe42Cr20Mo16Ni12C10 alloy powders was successfully bonded to a 316L stainless steel substrate through laser cladding. Various laser scanning speeds (4, 6, 8 mm/s) were employed to achieve the desired results. The coating consisted of ferrite and austenite with no undesired phase such as sigma (σ) or chi (χ). Notably, the sample synthesized at a laser scanning rate of 6 mm/s exhibited equal amounts of ferrite and austenite phases (approximately 50

Solidification processing of aluminum graphene composite is an attractive option for synthesis of metal matrix composites. Graphene reinforced aluminum metal matrix composites (GAMMCs) are of interest due to the low density and ultrahigh physical and mechanical properties of Graphene which can improve the properties of Al-Graphene composites. However, solidification processing of aluminum graphene composites has served challenges, including agglomeration of reinforcement and porosity resulting in decrease in properties above 0.five to three wt% graphene. Also, the graphene surface can react with molten aluminum alloys to form aluminum carbide. Challenges with particle distribution and porosity are frequently caused by the poor wetting of reinforcement by melt, requiring additions of selected wetting agents. The other problems include movement of reinforcement within the melt due to density differences and convection leading to nonuniform distribution of reinforcements. The graphene reinforcements can be pushed by solidifying interfaces under certain conditions during solidification leading to segregation of reinforcements in the interdendritic regions. The paper critically analyzes the above problems related to solidification processing of Aluminum- Graphene composites which has not been done in previous publications aluminum-graphene composites. The objective of this paper is to examine the challenges, and suggest possible solutions including addition of elements like silicon and magnesium to aluminum melt, coating graphene with metals like nickel and copper, controlling rate of advancement and nature of advancing solid liquid interface in a manner that they engulf graphene with dendrites or grains.

Melt pool geometry is a deterministic factor affecting the characteristics of metal Additive Manufacturing (AM) components. The wide array of physical and thermal phenomena involved during the formation of the AM melt pool, along with the great variety of alloy compositions and AM methods, coupled with the clear influence of multiple process parameters, make it difficult to predict the melt pool geometry under a given set of conditions. Therefore, using Artificial Intelligence (AI) approaches such as Machine Learning (ML) is necessary for accurate predictions. Using a physics-informed feature selection strategy along with the application of atomic features for the first time, this work aims to offer accurately trained models relying on existing high-fidelity data for most common alloys in AM academia and industry, i.e., 316L stainless steel, Ti6Al4V, and AlSi10Mg. Multiple ML algorithms were trained, and the results revealed that the average R2 and RMSE obtained by the K-fold cross-validation (K=5) were significantly enhanced when laser and material properties, inspired by the analytical models for AM melt pool geometry, were used as the model features. Removing the excess features and applying atomic features further enhanced the accuracy of the models. As a result, R2 for the XGBoost, CatBoost, and GPR models were 0.907, 0.889, and 0.882, respectively, while the hold-out cross-validation led to 0.978, 0.976, and 0.945, respectively. Furthermore, the results showed that the XGBoost model outperforms the Rosenthal equation. This approach provides a pathway to more accurately predict the properties of metal AM components.

In this study, effects of bonding time on microstructure, mechanical properties and corrosion resistance of transient liquid phase bonded Inconel 617 and AISI 310 alloys using a BNi-2 interlayer were investigated. TLP bonding was conducted at 1040 °C in a vacuum furnace and for bonding times of 15, 45 and 90 minutes. Then, microstructure, shear strength, fractured surface, hardness and corrosion resistance of the joints and the base metals were studied. The result showed that thickness of the diffusion affected zone increased with the bonding time. The optimal mechanical properties were achieved at bonding time of 45 minutes. This appeared to be due to completion of the isothermal solidification by this time. The maximum shear strength and hardness at the bonding time of 45 minutes were 618 MPa and 308 Vickers, respectively. Also, the number of intermetallic compounds formed increased resulting in a decrease in the shear strength of the joints. EIS and polarization corrosion tests on joints and base metals showed the highest corrosion resistance of the TLP-bonded sample at 45 minutes. At short bonding times, ASZ and ISZ acted as cathode and anode, respectively, causing pitting corrosion which is worse in the Cr and Mo poor zones.

This paper introduces and examines a new generation of chillers for judicious control of the solidification structure of cast metals and alloys. This innovative chiller makes use of the absorption of the latent heat of melting of a Phase Change Material (PCM) incorporated in the chiller. In this work, Al-4.5 wt%Cu melt was cast in sand molds fitted with a traditional solid steel chiller as well as this new type of chiller consisted of a steel container filled with a given amount of pure zinc as PCM. Effects of the PCM fitted chiller on the thermal history, solidification and structure of the castings were studied by experimental and computer simulation investigations. The optimum casting parameters and mold and chillers dimensions were selected using ProCast simulation software. Use of the PCM fitted chiller resulted in faster columnar-equiaxed transition, 27 %, 54 % and 40 % reduction in the length of the columnar zone and the primary and the secondary dendrite arm spacings, respectively, and about 30 % improvement in the hardness. Thermal gradients and cooling rates at different points of the PCM fitted casting were generally more than those in the traditionally chilled casting. Use of the PCM fitted chiller eliminated the formation of the feathery grains and reduced the formation of the undesired Fe-rich phases close to the chiller due to different thermal history of the castings. Segregation pattern and change of Growth Restriction Factor (GRF) along the castings were studied and related to the cooling and growth conditions experienced by each casting.

This study synthesized Sn-0.7wt.%Cu/Xwt.%SiO 2 nanocomposite solder by angular accumulative extrusion (AAE). AAE is a severe plastic deformation process used here to synthesize a metal matrix composite for the first time. The Sn-0.7wt.%Cu lead-free solder has proved to be an appropriate alternative for Sn–Pb solder due to its lower cost than other lead-free solders, good wetting and electrical conductivity, and high creep resistance. The characterization results showed that adding silica nanoparticles improved the solder properties compared to the monolithic sample. Compared to the monolithic sample, the tensile properties of as-extruded nanocomposite solder samples containing 0.5- and 1-wt% nanoparticles have increased by 22 and 12%, respectively. The joint shear strength of nanocomposite solders increased by 9% and 17%, tensile strength by 41% and 44% and microhardness by 14% and 32% after reflow for the samples containing 0.5 and 1% nanoparticles, compared to the monolithic sample, respectively. Moreover, adding nanosilica particles decreased the wetting angle with a copper substrate, refined the microstructure, and suppressed undesired intermetallic compound formation compared to the monolithic sample. Accordingly, the synthesis of nanocomposite solder by AAE has been successful.

The present research concerns fabrication of Al-4.3wt.%Cu metal syntactic foams using expanded perlite particles (EPPs). A gas pressure infiltration technique was employed to fabricate the aluminium syntactic foams under different infiltration temperatures and pressures. Ambient air pressure and 750 °C were identified as the favoured processing conditions for full infiltration of the melt. The average density and EP volume percentage of the fabricated foams were measured to be about 1.55 g/cm3 and 50.3%, respectively. Melt infiltration is believed to be mainly controlled by the breakage of the aluminium oxide layer on the melt surface and melt viscosity. Preferential infiltration of the melt between the mould wall and the EP particles bed complemented by radial melt infiltration toward the centre of the samples was identified. The effects of EP particles on growth of the nucleated primary α-aluminium phase were discussed. XRD and EDS analyses suggested some chemical reactions at the interface of EPPs with the molten aluminium. T6 heat treatment in the ambient atmosphere improved the average compressive tensile strength, plateau stress, and absorption capacity of the syntactic foams by more than 100%. Uniform deformation and similar densification strains (about 40%) of the as-fabricated and heat-treated syntactic foams during the compression test suggested uniform distribution of EP particles and metallic struts in the aluminium alloy matrix.

In this work, two types of CP Ti cubes with similar volumetric energy densities (VED) but different process parameters were produced using laser powder bed fusion (LPBF) method. The corrosion behavior of the fabricated specimens was investigated by conducting electrochemical impedance spectroscopy (EIS) and polarization experiments in simulated body fluid (SBF) solution at 37 °C. The results indicated that the microstructure and porosities, which are of great importance for biomedical applications, can be controlled by changing the process parameters even under constant energy densities. The sample produced with a lower laser power (E1) was featured with a higher level of porosity and thinner alpha laths, as compared with the sample fabricated with a higher laser power (E2). Moreover, results obtained from the bioactivity tests revealed that the sample produced with a higher laser power conferred a slight improvement in the bioactivity due to the higher amount of porosity. Lower laser power and hence higher porosity level promoted the formation of bone-like apatite on the surface of the printed specimens. The potentiodynamic polarization tests revealed inferior corrosion resistance for the fabricated sample with higher porosity. Moreover, the EIS results after different immersion times indicated that a stable oxide film was formed on the surface of samples for all immersion times. After 1 and 3 days of immersion, superior passivation behavior was observed for the sample fabricated with lower laser power. However, very similar impedance and phase values were observed for all the samples after 14 days of immersion.

Development of high-entropy alloys (HEAs) is one of the remarkable advancements in the progress of new materials. In recent years, continuous efforts have been made to design light weight high-entropy alloys (LWHEAs) with suitable microstructure and superior properties. This paper reports the preliminary results of a study aimed at design and development of a new low melting point LWHEA (LMLW-HEA) based on AlMgZnC-uMn alloy system without excessive intermetallic compounds formation. In this research, first, the initial chemical composition of the alloy was designed according to thermodynamic parameters, and then the alloy was melted in a resistance electric furnace. Since the thermodynamic indicators have been defined based on alloys containing 3d transition elements, formation of binary intermetallic compounds was predicted with the help of Midema model. To investigate the effects of cooling rate and heat treatment on the structure of the designed alloy, the molten alloy was poured into two different molds made of silica sand and steel, and both as cast samples were also heat treated. Microstructural features, mechanical properties and thermal stability of the samples were then examined. Density of the samples was measured to be less than 3.4 gr/cm3 which was very close to the theoretical density of the alloy. Structures of all the samples were complex and multi-phase and contained intermetallic (ordered solid solution) binary and ternary compounds including Mg7Zn3, MgZn2, Cu2Mg, Al2Cu, Mg32 (Al, Zn)49, Mg32Cu7Al47, Al25Mg37.5Zn37.5, and CuMgZn phases. The designed alloy was brittle under all the processing conditions. Compressive strength of the alloy reached to about 95 MPa, and its hardness was in the range of 110-120 HV. Oxidation resistance of the alloy was evaluated at a temperature about 30 C below its solidus temperature and no weight change was observed in the sample after 14 h. It is suggested that the designed alloy is a suitable candidate for high temperature applications not involving impact or cyclic loading.

Cast metal matrix nanocomposites (C-MMNCs), commonly made of light-weight aluminum or magnesium matrices, usually exhibit inferior fatigue behavior as compared to their monolithic alloys commonly owing to poor ductility and low toughness values caused by the addition of reinforcing nanoparticles. Strong inter-particle forces such as van der Waals, casting induced porosities, inadequate dispersibility of nanometric particles, and insufficient wetting in the reinforcement-matrix interfacial regions are of the key existing problems. The present study is aimed to deal with the high-cycle fatigue behavior of a novel ultrasonically stir-cast SiO2/A356 nanocomposite wherein a C-MMNC with simultaneously enhanced static and fatigue properties was developed. Due to good ultrasonic dispersion and distribution of nanometric particles, the developed composite materials exhibited higher ductility values, being a dominant parameter to dictate the fatigue response. While the addition of reinforcing particles to a given melt usually leads to an inferior fatigue response, the obtained results revealed that proper ultrasonication can effectively reduce porosities, de-agglomerate solid reinforcements, wet and disperse them uniformly in the matrix and enhance fatigue performance significantly.

In this study, short carbon fiber (C SF s) reinforced Al-Si alloy matrix composites were produced using a combination of vortex and squeeze casting processes. Effects of the reinforcement addition, applied pressure and fiber coating on density, porosity content, reinforcement distribution, hardness and tribological characteristics of the composites were investigated. It was found that the composites reinforced with uncoated C SF s and without pressure application were inferior to the monolithic samples in terms of porosity content, hardness and tribological properties. Majority of the uncoated C SF s in the matrix were agglomerated in bundles where the melt had not been able to fill the inter-bundle and intra-bundle spacings. Squeeze casting reduced the degree of reinforcement agglomeration considerably and improved the dispersion of the uncoated C SF s in the matrix and the penetration of the melt into the inter-bundle and intra-bundle areas of the C SF s. These resulted in improved microstructure and mechanical properties. Squeeze casting reduced the wear intensity by reducing the volumetric defects in the matrix and increasing the resistance to plastic deformation of the cast specimens. The best results were achieved when the C SF s were coated with a 7 μm Ni-P electroless coating. In this case, no C SF bundles were detected and a rather uniform dispersion of coated C SF s in the matrix with defect free interfaces was achieved. This sample realized the least porosity content among the composite samples, as well as the highest hardness, lowest wear rate and smallest friction coefficient. Different wear mechanisms including abrasive, delamination and adhesion wear mechanisms were detected on the worn surfaces of the samples.

Alloy design using Additive Manufacturing (AM) methods is an interesting research area attracting the attention of researchers across the world. Formation of strong texture, columnar grains, and chemical inhomogeneity in AM-designed alloys are among the serious challenges dealt with in various research works. This paper addresses these challenges for the first time for a Ti6Al4V–7Cu alloy produced via Electron Beam Powder Bed Fusion (EB-PBF) method following an in-situ alloying approach. In this work, a mixture of Ti6Al4V and elemental Cu powders was used as the feedstock. The results showed a relatively homogenous Cu distribution in the product due to the large melt pool created during the EB-PBF process, a development indicating the method's applicability for in-situ alloying and alloy design. The prior β columnar grains were effectively converted into equiaxed grains due to a constitutionally supercooled zone created by the rejection of Cu solutes in front of the solidification front and a relatively lower thermal gradient during EB-PBF compared with other AM processes. The addition of Cu enhanced the microhardness of Ti6Al4V, which could be considered an outcome of equiaxed grain formation, solid solution strengthening mechanism, and Ti2Cu intermetallic precipitation.