Cast Alloy Research Articles

Thermodynamic databases of Ti-Al-Fe-V quaternary alloy systems and its application

Pandat software based on Calculations of phase diagram (CALPHAD) was used in this study. Six binary systems and four ternary systems in the Ti-Al-Fe-V system were evaluated, compared, and optimized. A thermodynamic database of Ti-Al-Fe-V titanium alloys was established by selecting the most recent, accurate, and self-consistent thermodynamic parameters. The database was used to simulate the organization of equilibrium solidification and non-equilibrium solidification alloys of Ti-10V-2Fe-3Al, Ti-10V-3Al-1Fe and Ti-10V-3Al. The precipitated phase fractions of Ti-10V-2Fe-3Al at different temperatures were calculated using the database. The effect of different Fe contents and aging temperatures on the phase composition of the Ti-10V-2Fe-3Al alloy is given in conjunction with the calculated results. There is good agreement with the experimental results for the heat treatment regimens given by the calculations. The above results show that thermodynamic calculations based on phase diagrams can guide the formulation of process parameters for alloy casting and heat treatment. The established thermodynamic database for Ti-Al-Fe-V titanium alloys is accurate and reliable.

Determination of Porosity-A Casting Defect Occurrence in Green-Sand Casting of Al-Si5-Cu3 by the Taguchi Method

Porosity is a significant concern in Al-Si5-Cu3, aluminum alloy casting, tending to considerably more scrap outcomes and limiting parts use in critical applications due to porosity. This defect is directly relevant to the manufacturing process thus its occurrence is closely tied to green sand-casting process parameters. Here implementing of Taguchi method offers substantial porosity reduction mapping during casting with different input parameters. A combined experiment has been carried out using Taguchi’s L27 orthogonal array (OA) to study the main effect and interaction effect of all five parameters. In a thick-walled sample casting, pouring temperature and pouring time significantly affect porosity reduction. Pouring temperature having F-Value of 8.47 and a low P-Value of 0.003, and F-Value of 5.76 and a corresponding P-Value of 0.013 of the pouring time, indicating its influential role in explaining the variation in both Average Porosity and S/N Ratio Degassing time and mould temperatures have marginal effects, while crucible volume hold minimally influences porosity. The interaction between pouring temperature, pouring time, and crucible volume in green sand casting significantly impacts the output, indicating significance influential factors for porosity occurrence, as their p-values are below 0.05 or very close to it. Assessing the anticipated enhancements in quality and the potential for cost savings based on optimal parameters forecasts a decrease in porosity and minimized losses prior to conducting experimental trials.

Thermal Analysis of Different Piston Head Profiles by using FEM

The objective of this research work is to optimize the stress variations at the top of the piston in real engine conditions. During this pressure analysis on the examined surface of the piston, the thermal behavior is examined. The operating gas pressure, temperature and piston material functions are used as investigation functions. The analyzes carried out showed that the upper part of the piston could be damaged or broken due to the temperature caused by the working conditions, as the replacement of damaged or non-functioning parts is very expensive and usually difficult to obtain. Concave and convex piston profile designed in Solid Work 2023, used to design the piston geometry and for FEM analysis to optimize the thermal behavior of the used ANSYS R23.0 piston. Aluminum alloy and gray cast iron material for piston construction. Stress and displacement are analyzed for the piston by applying pressure to it in the structural analysis. By observing the results of the analysis, we can decide whether the piston we are designing is safe or not under the applied load conditions. Heat flow and thermal temperature distribution are analyzed using piston surface temperatures in thermal analysis.

PHYSIOLOGICAL AND SOCIO-ECONOMIC SATISFACTIONLEVEL OF PATIENTS FOR ACRYLIC AND CAST ALLOY DENTURES

Background: The ultimate loss of dentition creates lot of oral problems for edentulous patients which can be prevented with the provision of acrylic or cast alloy denture but patient satisfaction level attributed to these dentures is still unknown. We evaluated patient satisfaction level regarding aesthetics, pain, cost, retention, comfort and speech between acrylic and cast alloy denture wearers. Methods: Freshly edentulous patients wearing complete dentures with acrylic resin denture (AD) (n=65) and Co-Cr cast alloy denture (CD) (n=65) took part in study. Smart Patient Satisfaction Questionnaire was used to investigate satisfaction of these patients after one month (AD-1 and CD-1) and then after 3 months (AD-3 and CD-3). Scoring system 0=Not-Satisfied, 1=Satisfied and 2=Well Satisfied was used to evaluate general satisfaction of patients in both groups regarding speech, taste, pain, aesthetics, comfort, cost, and retention. Results: Patient satisfaction level between AD and CD wearers displayed insignificant differences with respect to aesthetics (p=0.614), pain (p=0.842), retention (p=0.852), comfort (p=0.842), speech (p=0.943), and taste (p=0.753). Patient satisfaction level between AD and CD users related to cost was significant (p=0.001) depicting that AD group was more satisfied with cost as compared to CD users. Conclusions: Both groups were satisfied with their aesthetics, pain control, retention, comfort, speech, and taste but patients using AD were found to be more satisfied with cost as compared to CD users who found these dentures quite expensive. Pak J Physiol 2023;19(4):6-10

Effects of Cr-addition on ageing response of an Al–Si–Mg die cast alloy

Chromium (Cr) is rarely added to Al–Si die cast alloys as it has a strong tendency to induce the formation of coarse-sized sludge particles. In the present study, high pressure die-cast samples made of Al-7wt.%Si–Cr–Mg alloys with varied Fe contents (0.11 wt%, 0.26 wt% and 0.32 wt%) were tensile tested under as-cast and T5 heat-treated conditions, in comparison to those made of Al-7wt.% Si–Mn–Mg alloy with a constant Fe content (0.11 wt%). The results demonstrated that under the as-cast condition, the Al–Si–Cr alloys with higher Fe contents can achieve comparable tensile properties as the Al–Si–Mn alloy with strictly controlled Fe level. However, after a T5 heat treatment (205 °C for 60 min), the increment in yield strength is less for the Al–Si–Cr alloys in relative to the Al–Si–Mn alloy, regardless of Fe contents. Scanning electron and scanning transmission electron microscopic characterizations were conducted on the as-cast and heat-treated microstructures, aiming to understand the undermined ageing response caused by Cr addition.

Numerical Simulation on Solidification during Vertical Centrifugal Casting Process for TC4 Alloy Wheel Hub with Enhanced Mechanical Properties.

The Ti-6Al-4V (TC4) alloy wheel hub has exhibited some defects that affect the properties during the vertical centrifugal casting process. Therefore, the analysis of the solidification process would contribute to solving the above-mentioned problems. In this study, an orthogonal experimental design was employed to optimize the process parameters (rotational speed, mold preheating temperature, and pouring temperature) of the vertical centrifugal casting method. The effects of process parameters on the velocity field, temperature field, and total shrinkage porosity during the solidification process were explored, and the microstructure and mechanical properties of the wheel hub prepared by the vertical centrifugal casting method were also investigated. The results showed that the rotational speed mainly induced the change of the velocity field. The pouring temperature and mold preheating temperature affected the temperature field and solidification time. Based on the analysis of the orthogonal experiment, the optimal parameters were confirmed as a rotational speed of 225 rpm, mold preheating temperature of 400 °C, and pouring temperature of 1750 °C, respectively. The simulation results of total shrinkage porosity were in agreement with the experiment results. The wheel hub was composed of nonuniform α and β phases. The lath α phase precipitated from larger β grains with different orientations. Compared with the other samples at different locations, the α phase in the PM sample (middle of the TC4 wheel hub) displayed high peak intensity and uniformly distributed β phase along the radial direction of the wheel hub. Moreover, the PM sample revealed a higher tensile strength of 820 MPa and similar Vickers hardness of 318 HV compared with the other samples at different locations, which were higher than those of rolling and extrusion molding. This experiment design would provide a good reference for the vertical centrifugal casting of the TC4 alloy.

The effect of modification with nanocompositions on the structure and properties of foundry silumins


 Abstract. Problem. The difficulty of solving the problem lies not only in the improved quality of casting alloys, but also in the development of recommendations for achieving stability of the chemical composition, refining the structure, and increasing the mechanical and technological properties of castings. Goal. The goal of the work is to achieve a stable dispersed structure and increase the complex of mechanical properties of foundry silumins. Methodology. Based on the Al – Si influence diagram, the choice of cast aluminum alloys for modification with nanocompositions is substantiated. The technology of modification with nanodisperse compositions consisted in introducing powders of the complex nanomodifier Mg2Si+SiС into the aluminum melt. A mixture of Mg2Si+SiC nanopowders with a particle size of 50...100 nm, obtained by plasma chemical synthesis, was mixed for several hours in a special attritor with successive pressing of modifier tablets on an automatic press. Results. The technological process of modifying aluminum melts with a complex modifier was developed, the temperature and time parameters of the process were determined. Brinell hardness was measured on samples of AL4 and AL4C alloys, 25x25 mm in size. As a result of the obtained data, it is observed that in the modified samples of the AL4 alloy, the hardness increased by 6.9%, and in the AL4C samples – by 4.8%. The obtained hardness measurement data are consistent with the results of testing the strength properties of alloys before and after modification. Originality. In the modified alloys, a higher fluidity than in the initial state and a homogeneous dispersed microstructure were obtained. Practical value. In the modified alloys, an increase in strength properties was achieved: σv by 9 - 10%; σ0.2 by 11-12%, while maintaining the level of plasticity. The impact strength of modified alloys is significantly increased by 20-30%. As a result of the conducted studies of the structure and properties of cast alloys AL4 and AL4C, the effect of modification with nanodisperse compositions was confirmed.

Clustering characteristics of Fe-rich intermetallics in high vacuum die cast AlSiMgMn alloys with high resolution μ-CT inspection

The AlSiMgMn alloys with different Fe and Mn contents were prepared with high vacuum die casting (HVDC) process. The Fe-rich intermetallics in the surface layer and center of the alloys were inspected with high-resolution 3D X-ray micro-computed tomography (μ-CT), and the growth mechanism of the primary Fe-rich phase was analyzed through their different 3D morphographies. By combining Bisecting K-means and DBSCAN (Density-Based Spatial Clustering of Applications with Noise) methods, the intermetallic clusters in the surface layer and center were quantified. The results show that the primary Fe-rich intermetallics were characterized as hexahedron and octagonal dendrite shapes with large size while the eutectic Fe-rich intermetallics were polyhedron and Chinese-script shapes. When Fe and Mn contents of the alloys were lower, the intermetallic clusters in the surface layer were with less cluster number and larger intermetallic distances showing uniform distribution whereas the clusters in the center were more and had shorter distances. In the case of alloys with higher Fe and Mn contents, the intermetallics showed clustering distribution in both the surface layer and center. The mechanism for the intermetallic cluster formation in the surface layer and center was further discussed.

“Branched” structural transformation of the L12-Al3Zr phase manipulated by Cu substitution/segregation in the Al-Cu-Zr alloy system

The effect of Cu on the evolution of the Al3Zr phase in an Al-Cu-Zr cast alloy during solution treatment at 500 °C has been thoroughly studied by combining atomic resolution high-angle annular dark-field scanning transmission electron microscopy, energy-dispersive X-ray spectroscopy and first-principles calculations. The heat treatment initially produces a pure L12-Al3Zr microstructure, allowing for about 13 % Cu to be incorporated in the dispersoid. Cu incorporation increases the energy barrier for anti-phase boundary (APB) activation, thus stabilizing the L12 structure. Additional heating leads to a Cu-induced “branched” path for the L12 structural transformation, with the latter process accelerated once the first APB has been created. Cu atoms may either (i) be repelled by the APBs, promoting the transformation to a Cu-poor D023 phase, or (ii) they may segregate at one Al-Zr layer adjacent to the APB, promoting a transformation to a new thermodynamically favored phase, Al4CuZr, formed when these segregation layers are periodically arranged. Theoretical studies suggest that the branching of the L12 transformation path is linked to the speed at which an APB is created, with Cu attraction triggered by a comparatively slow process. This unexpected transformation behavior of the L12-Al3Zr phase opens a new path to understanding, and potentially regulating the Al3Zr dispersoid evolution for high temperature applications.

Powder production, FAST processing and properties of a Nb-silicide based alloy for high temperature aerospace applications

A Nb-silicide based alloy with nominal composition Nb–18Ti–22Si–6Mo-1.5Cr–2Sn-1Hf (at. %), designed for high temperature aerospace applications, was produced via a powder metallurgy (PM) route. The raw elements were arc melted, crushed, and milled to powder, then consolidated using Field Assisted Sintering Technology (FAST). The compressive creep of the alloy was evaluated using electro-thermal mechanical testing (ETMT). The study demonstrated the production of larger 60 mm diameter samples, with potential for further scale up. The microstructure of the FAST alloy, which is comprised of bcc Nbss and tetragonal αNb5Si3 was more homogenous compared with the cast alloy, with some interstitial contamination that occurred during powder production. The FAST alloy had lower density than state of the art Ni-based superalloys and refractory metal complex concentrated alloys (RCCAs) and high entropy alloys (RHEAs), and its yield strength and specific yield strength was higher than those of the latter metallic Ultra high temperature materials (UHTMs) and comparable to those of Nb-silicide based alloys with B addition. The stress exponent n in compressive creep was in the range 1.7–2.6, similar to that of binary Nb–10Si and Nb–16Si alloys and its creep rate at 1200 °C and 100 MPa was similar to that of the MASC alloy (Nb–25Ti–16Si-8Hf-2Al–2Cr (at.%)). Like the latter, the creep of the FAST alloy did not meet the creep goal.

A hot tearing propagation model for steel

Hot tearing is a significant challenge in material preparation process, including high-performance alloy casting, large ingot production and additive manufacturing, etc. However, the propagation process of hot tears, especially in steel, is still unclear at present. This study proposed a new model for hot tearing propagation that considers the energy balance, the relationship between the propagating mode and the growth rate of hot tears when they undergo irreversible and rapid propagation. To evaluate this model, a new testing device was developed and the hot tearing behaviors of low and high carbon steels were observed. The tests demonstrated a notable correlation with the model. Furthermore, a new criterion for propagation of hot tearing was put forward. This work provides a more comprehensive physical model and criteria for simulating and predicting the formation of hot tears.

A new generation of metal chillers to control the solidification structure of Al-4.5 wt%Cu alloy

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.

Hierarchical Hybrid Coatings with Drug-Eluting Capacity for Mg Alloy Biomaterials.

A hierarchical hybrid coating (HHC) comprising a ceramic oxide layer and two biodegradable polymeric (polycaprolactone, PCL) layers has been developed on Mg3Zn0.4Ca cast alloy in order to provide a controlled degradation rate and functionality by creating a favorable porous surface topography for cell adhesion. The inner, ceramic layer formed by plasma electrolytic oxidation (PEO) has been enriched in bioactive elements (Ca, P, Si). The intermediate PCL layer sealed the defect in the PEO layer and the outer microporous PCL layer loaded with the appropriate active molecule, thus providing drug-eluting capacity. Morphological, chemical, and biological characterizations of the manufactured coatings loaded with ciprofloxacin (CIP) and paracetamol (PAR) have been carried out. In vitro assays with cell lines relevant for cardiovascular implants and bone prosthesis (endothelial cells and premyoblasts) showed that the drug-loaded coating allows for cell proliferation and viability. The study of CIP and PAR cytotoxicity and release rate indicated that the porous PCL layer does not release concentrations detrimental to the cells. However, complete system assays revealed that corrosion behavior and increase of the pH negatively affects cell viability. H2 evolution during corrosion of Mg alloy substrate generates blisters in PCL layer that accelerate the corrosion locally in crevice microenvironment. A detailed mechanism of the system degradation is disclosed. The accelerated degradation of the developed system may present interest for its further adaptation to new cancer therapy strategies.

Effect of Sn microalloying on microstructure and mechanical properties of Mg-11Gd-1Zn-0.5Zr alloy

The effect of Sn microalloying on the microstructure and mechanical properties of the Mg-Gd-Zn-Zr alloy has been systematically investigated. The grain size of the cast alloy was found to be coarse. The two alloys were mainly composed of α-Mg and (Mg, Zn)3Gd phases, and the addition of 0.5 % Sn also caused a small amount of Sn3Gd5 phases to appear. In the subsequent homogenization heat treatment at 500 °C, adding Sn promoted the formation of many lamellar 14H-LPSO phases. After undergoing three rounds of hot rolling, the Sn-containing alloy exhibited a refined grain size and a significant reduction in the volume fraction of twins, mainly due to the particle-stimulated nucleation (PSN) mechanism and the inhibiting effect of LPSO on twins. In addition, the ultimate tensile strength (UTS) of the alloy (380 ± 1 MPa) was significantly increased by the addition of Sn, although the age hardening effect was prolonged. The high strength was attributed to the dispersion distribution of fine chain-like β′ structure, which was conductive to the movement of pinning basal dislocations.

Microstructure and mechanical property of A356 cast remanufactured by ultrasonic frequency pulsed TIG process

Remanufacturing quality is critical to the service performance of aluminum alloy castings. Here, casted A356 Al7Si0.3 Mg alloy was remanufactured by using ultrasonic frequency pulsed (UFP) TIG deposition process. The heterogeneous microstructure evolution, hardness distribution, and tensile behavior of the repaired part were investigated and discussed. The UTS, YS and elongation of the UFP-TIG remanufactured A356 are 183 MPa, 121 MPa and 3.3 %, respectively. The repaired part shows a strength coefficient of 0.93 and superior ductility over the cast.

Research on accelerating artificial aging process of Al-5Mg-3Zn-1Cu cast alloy by natural aging

In this study, natural aging (NA) has been carried out to accelerate the artificial aging process and enhance the mechanical properties of Al-5Mg-3Zn-1Cu Cast Alloys. The studies show that, during the first 120 h of natural aging, the supersaturated Al-5Mg-3Zn-1Cu cast alloy after the solution heat treatment is unstable, and an amount of nano solute clusters are precipitated from the matrix, which leads to the rapid increase of the hardness of the alloy. Moreover, introducing 120 h natural aging before artificial aging significantly shortens the peaked-aged time and improves the mechanical properties of peak-aged alloys, especially at 150 and 175 ℃ artificial aging temperatures. It is considered that the solute clusters precipitating in the matrix during natural aging and the precipitates formed during artificial aging co-develop to accelerate the artificial aging process of the alloy. In addition, the increase in the number of precipitates reduces the inter-precipitate spacing, which is inversely proportional to the strength of the alloy, resulting in a significant increase in the strength of the alloy. This research suggests that a combination of natural and artificial aging is an effective and economical method for achieving optimized mechanical properties for the Al-5Mg-3Zn-1Cu cast alloy.

Effect of Alloying Additives and Moulding Technology on Microstructure, Tightness, and Mechanical Properties of CuSn10 Bronze.

Thise research was conducted to determine the impact of the applied casting technology, mould and alloying additives on the tightness of the CuSn10 cast alloy. Under industrial conditions, a series of experimental melts were made that were characterised by varying the concentrations of the main alloying element (Sn) and the introduced alloying additives (Si, Zn, Zr). The mould was made from green sand and used the CO2 moulding process. To assess the influence of the alloying additives, a metallographic analysis of the studied alloy was carried out, and the alloy's microstructure was examined using optical and scanning electron microscopy. The introduced alloying additives affected the properties and microstructure of the studied alloy. As alloying additives, zirconium resulted in a visible refinement of the microstructure, while silicon improved the fluidity and quality of the casting's external surface. The use of alloying additives and moulds made using different technologies is intended to improve the structure of the tin bronze castings produced and to find the best solution to significantly eliminate the lack of leakage of the castings. The castings were subjected to mechanical processing, and a leak test was performed using the pressure drop method. The conducted research allowed us to determine which technology, applied to production, will bring about a reduction in the problem and will inform further investigations.

A simple procedure to assess the Complete Melt Quality in aluminium castings: implementation in a die-casting and a rheo-casting

ABSTRACT A new simple approach was developed to assess the Complete Melt Quality of aluminium cast alloys throughout the production line. The approach relies on the concurrent use of reduced pressure tests (RPT) and tensile tests at each station in the production line when the melt is transferred and/or processed. These tests can be used to determine the source of melt-related problems in the production line. Two case studies from the procedure of both an aluminium die-casting and a rheo-casting plant showed that melts were significantly damaged in the tower furnace and got progressively more damaged through the production line proven by the RPT, tensile test, and fracture surface analysis results.

Tailoring the microstructure and mechanical properties of LPSO-containing Mg–Ni cast alloy by yttrium addition

The effect of yttrium addition on the evolution of phases, grain refinement, and mechanical behavior of Mg-0.5Ni cast alloy was investigated. It was observed that while the base alloy contained a eutectic structure containing α-Mg and Mg2Ni, in the Y-containing alloys, the long period stacking ordered (LPSO) structures and Mg24Y5 phase appeared at the expense of the eutectic structure. The dendrite arm spacing (DAS) was significantly refined, so that adding 0.5 and 2 at% Y led to the refinement of DAS from 141 to 56 and 22 μm, respectively. Accordingly, hardness, tensile and shear strength were improved, being successfully represented by the Hall-Petch-type relationships in terms of DAS. The highest elongation to failure in tensile tests was obtained at 0.5 % Y addition, which was ascribed to the refinement of microstructure and partial replacement of the deleterious α-Mg + Mg2Ni eutectic structure by the LPSO phase. However, further addition of Y led to the formation of intergranular interconnected network of LPSO structure with deteriorated ductility. Therefore, the best strength-ductility synergy was obtained for the Mg99Ni0.5Y0.5 alloy, as evaluated by the tensile toughness. Finally, the tensile and shear properties were correlated according to the von-Mises criterion.

Insight into the fracture behaviour and mechanical response of ECAP processed cast and LPBF AlSi10Mg alloy

This paper presents a comparative analysis of the microstructure, tensile deformation and fracture mechanisms of an ECAP-processed AlSi10Mg alloy produced by two different methods: selective laser melting (SLM) and casting. The evolution of the microstructure was investigated using optical microscopy (OM), scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). In addition, internal structural defects were analysed using X-ray computed tomography scans (CT). To investigate the mechanical properties and crack propagation during tensile deformation, a real-time visualization through in-situ tensile CT scans, along with the loading–unloading-reloading tensile test (LUR) was employed. The results showed significant differences in the mechanical property between the two ECAP-processed samples. Specifically, the SLM sample exhibited an approximately 50 % higher tensile strength of 370 MPa and a remarkable elongation at break of 12 %. Detailed microstructural analysis showed that the additional work hardening occurred mainly in the hetero-zones, where the accumulation of geometrically necessary dislocations developed back and forward stresses, which together led to the hetero-deformation induced (HDI) stresses. Further quantification of the (HDI) stress derived from the loading–unloading-reloading tensile test (LUR) confirmed origin of the additional strain hardening in the SLM specimen. Fractographic analysis showed that the poor tensile ductility of the ECAP-processed cast specimen was primarily due to the low bonding between Al and Si particles, resulting in premature fracture. In contrast, the ECAP-processed SLM specimen fractured predominantly along the softer heat-affected zones (HAZ).