Properties Of Castings Research Articles

Microstructure and Mechanical Properties of Cast Al-15Mg2Si-8Si-Based Alloy with Various Cr-Sb Ratio Addition

Microstructure and Mechanical Properties of Cast Al-15Mg2Si-8Si-Based Alloy with Various Cr-Sb Ratio Addition

Novel Cast and Wrought Al-3Zn-3Mg-3Cu-Zr-Y(Er) Alloys with Improved Heat Resistance

The main weaknesses of commercial high-strength Al-Zn-Mg-Cu-based alloys are the low casting properties, corrosion and heat resistance. Al-Zn-Mg-Cu-based alloys with Zn/Mg ratio equal to 1 combine good strength, corrosion and heat resistance. Al alloys with atomic ratio Cu/Y(Er) equal to 4 have a narrow solidification range and high solidus temperature. Two basic principles were taken into consideration to develop novel heat-resistant Al-Zn-Mg-Cu-based alloys with improved casting properties: 1—mass ratio of Zn/Mg = 1, and 2—atomic ratio of Cu/Y(Er) = 4. The microstructure, phase transformation and tensile properties of the novel cast and wrought Al–3Zn–3Mg–3Cu–0.2Zr–Y(Er) alloys were investigated. The structure and phase composition were investigated via thermodynamic calculation, optical and scanning electron microscopy and X-ray diffraction methods. A two-step solution treatment with higher temperature in the second step provides a microstructure with better elongation, making possible to increase the hot rolling temperature of the Y or Er-containing alloys. The yield strength (YS) of the alloys decreased insignificantly from 270 to 290 MPa at room temperature to 225 to 260 MPa at 200 °C after casting, solution treatment, water quenching and aging. A better combination of the YS = 291–345 MPa and elongation (El.) (11–14.8%) was achieved in the Al3Zn3Mg3CuY and Al3Zn3Mg3CuEr alloys after solution treatment, rolling, recrystallization annealing, water quenching and aging compared with the Al3Zn3Mg3Cu alloy with YS = 245–340 MPa and El. = 6.8–12.5%.

Investigation of Phase Transformation and Mechanical Properties of A356 Alloy with Cu and Zr Addition during Heat Treatment

Cast A356(Al-Si-Mg) alloys are widely used in automotive and general applications because of their mechanical properties and castability. Al-Si-Mg-(Cu) alloys typically lose their strength above 170 o C due to coarsening of precipitates, which limits their application to components. To maintain their strength at elevated temperature, Al-Si-Mg-(Cu) alloys are modified by adding transitional metals. Several studies have been carried out to evaluate the effect of Zr addition on the high temperature mechanical properties of cast Al-Si alloys because Zr can form thermally stable phases such as Al3Zr. Despite the relative studies on the influence of Cu and Zr on the mechanical properties of cast Al-Si-Mg-(Cu) alloys, investigations of the effect of Zr on the phase transformations and the mechanical properties during heat treatment remains limited. In this study, the effects of added Cu and Zr on the phase transformations and the mechanical performance during heat treatment of A356 cast alloy were investigated. Needle-like and block-like (Al,Si)3(Ti,Zr) dispersoids formed as some Si and Ti replaced Al and Zr in Al3Zr crystal structures were generally observed. Furthermore, with increasing solution treatment time, the size of Zr dispersoids was reduced, and smaller Zr particles were precipitated at the same time, which caused a decrease in the area fraction of the Zr dispersoids. In addition, the metastable L12 structures of Zr dispersoids in Al-Si-Mg-Cu-Zr alloys were transformed into stable D023 during solution heat treatment as the Cu addition accelerated the transformation. Tensile and low-cycle fatigue (LCF) tests were performed to reveal the effects of (Al,Si)3(Ti,Zr) dispersoids on mechanical properties. As a result, elongation at elevated temperature was highly increased, while maintaining strength, according to the increase in solution heat treatment time, which improved low-cycle fatigue properties.

Comparison of wear and mechanical properties of cast and 3D printed CuSn10 bronze alloy

Abstract This paper aims to provide a comparison between properties of CuSn10 bronze alloy produced by two methods: FDM (fused deposition modelling) and casting. Wear behavior, mechanical performance and microstructure of CuSn10 alloy produced by FDM and casting methods were determined and compared. 3D printed parts were sintered at 875 °C for 5 h and casting was done at 1200 °C. The amount of porosity was determined by the metallographic cross-sectional examination. Vicker’s hardness, wear and tensile properties of samples were determined. As a result, the porosity value of the CuSn10 alloy produced by the FDM technique was determined as 5.07 ± 0.53%. Tensile strength values were 233.75 ± 18.48 MPa and 349.04 ± 5.10 MPa for CuSn10 alloys produced by FDM and casting methods respectively. While adhesive wear occurs in both production methods, it was observed that the FDM method reduced the wear resistance.

Effect of Ti content on microstructures and mechanical properties of cast Al-2Li-2Cu-0.5Mg alloy

Effect of Ti content on microstructures and mechanical properties of cast Al-2Li-2Cu-0.5Mg alloy

Analysis of Vibration, Deflection Angle and Surface Roughness in Water-Jet Cutting of AZ91D Magnesium Alloy and Simulation of Selected Surface Roughness Parameters Using ANN.

The use of magnesium alloys in various industries and commerce is increasing due to their properties such as high strength and casting properties, high vibration damping capability, good shielding of electromagnetic radiation and high machinability. Conventional machining methods can, however, pose a risk of ignition. AWJM is a safe alternative to conventional machining, but the deflection and vibration of the water jet can affect surface quality. Therefore, the aim of this study was to investigate the effects of selected AWJM parameters on the surface quality and vibration of machined magnesium alloys. Jet deflection angle, surface roughness parameters and vibration during AWJM were investigated. The findings showed that higher skewness occurred at a lower abrasive flow rate, while higher average values of the Sku roughness parameter were obtained at ma = 8 g/s in the range of 60-140 mm/min. It was also observed that higher vibration values occurred at ma = 8 g/s. The input parameters for creating an artificial neural network (ANN) model used in this study were the cutting speed vf and the mass flow rate ma. The results of this study provided valuable insights into ways of ensuring a safe and efficient machining environment for magnesium alloys. The use of ANN modeling for predicting the vibration and surface roughness of AZ91D magnesium alloy after water-jet cutting could be an effective tool for optimizing AWJM parameters.

Study of high temperature aging of cast nickel alloy structure and properties

The paper presents the results of a study of changes in the structure and strength properties of a heat-resistant nickel alloy after various periods of operation in a gas turbine engine. It is shown that after 25,000 hours of operation, irreversible changes occur in the microstructure of the alloy, which adversely affect the performance of the parts. Ensuring the stability of the structural state and mechanical properties are very important in assessing the reliability and extending the service life. The results of a study of the effect of heat treatment parameters on the structural characteristics of the CrNi65CoMoWAlTi alloy are presented, and an assessment is made of the effect of structural parameters on mechanical properties. Timely application of recovery technologies can extend the service life of products.

Analysis of the slurry and ceramic properties for investment casting obtained with domestic colloidal silica binders

The quality of cast parts produced by investment casting is largely determined by the quality of the ceramic molds. Currently, aircraft and engine building enterprises are switching to an environmentally friendly colloidal silica binders for the manufacture of ceramic molds. In this work, the dynamic and relative viscosity of slurries prepared using fused silica powder and colloidal silica binders of the VT13-02U (Vakuumteh LLC), Stavroform VS (Polymet LLC), UltraCast One + and UltraCast Prime (both Technopark LLC) manufacturers were determined. It is shown that the slurries prepared on the considered binders have similar viscosity values, and in their rheological properties they are close to Newtonian liquids. The values of dynamic and relative viscosity at a binder content of 400 mL per 1 kg of fused silica powder were ~732 mPa·s and ~380 s, respectively. With an increase in the binder content to 600 mL per 1 kg of fused silica powder, the dynamic and relative viscosity decreased to ~70 mPa·s and ~16 s, respectively. An equation was also found that relates the dynamic viscosity determined using a rotational viscometer and the relative viscosity determined using the VZ-4 viscosimeter. The mechanical properties were determined during three-point bending tests on ceramic samples obtained using slurries on the above-mentioned colloidal silica binders and fused silica stucco. Samples obtained on binders VT13-02U, Stavroform VS and UltraCast One+ showed very similar bending strength values, namely 3.5–4.3 MPa after drying and 5.8–6.1 MPa after firing. Due to the presence of a polymer addition in the binder, the ceramic samples obtained on the UltraCast Prime binder had higher values of bending strength after drying and after firing – 6.4 and 7.2 MPa, respectively. It was also shown that with an increase in the viscosity of the slurry and a decrease in the fraction of fused silica stucco, the strength of the samples increases. The lowest surface roughness was observed for samples obtained with UltraCast grade binders.

Subversion of Casteism in Sajitha Madathil’s Kali Natakam: A Dalit Feminist Study

The feminist play Kali Natakam by Sajitha Madathil explores the injustices encountered by women in a ‘progressive society’ through Mudiyettu, a ritual dance performed in Kali Temples in Central Kerala. But is gender inequality the only visible problem in the play? Do mainstream feminist studies overshadow the issue of caste discrimination? Madathil’s play, Kali Natakam, is studied using the framework of Dalit feminism to understand the triple oppression Dalit women experience based on their caste, gender and race differences. Through an amalgamation of the myth of Kali and Darika, and a portrayal of contemporary society, the play complicates the notion of gender and caste discrimination. This article uses the concept of ‘intersectionality,’ introduced by Kimberlé Crenshaw in 1989, to understand the play in the dimensions of gender, caste and race. The basis of Dalit feminism is the testimonies given by Dalit women revealing how their everyday lives differed from those of non-Dalit women. First-person narratives lead in building the canvas of feminist thought in connection with caste identity. And how monopolizing gender by sideling race and caste differences ends in shunning some of the significant concerns and problems of women of different communities, especially Dalits. Considering the gender and caste element, a Dalit feminist analysis becomes the most appropriate way to study the play instead of doing separate studies. Recognizing the intersectionality in the play leads to comprehending the complexities of discrimination operating at multiple levels.

Investigations on microstructure and mechanical properties of cast Mg-Gd-Y-Zn-Zr-Nd alloy

Different solution treatments were carried out on the semi-continuously cast Mg-9.55Gd-2.27Y-1.28Zn-0.55Zr-0.11Nd (wt.%) alloy at temperatures of 480 °C, 500 °C, and 520 °C. It was found that the different solution treatment temperatures led to different phase constitutions of the alloy. The Mg3RE-type eutectic phases transform into long period stacking order (LPSO) phases with various morphologies after solution treatment. Increasing the solution temperature resulted in larger grain size, greater number of lamellar LPSO phases, and segregation of Zr element. Block LPSO phases also shifted to rod LPSO phase. After ageing treatment, the special spatial structure consisting of prismatic β′ precipitates, basal γ′ precipitates, and lamellar LPSO phases hindered dislocation movement effectively, leading to high strength.However, the accumulation of massive dislocations promoted the premature formation of cracks at the grain boundary and LPSO/Mg matrix interface, resulting in a rapid decrease in ductility of the alloy. After solution treatment at 480 °C for 12 h and aged at 200 °C for 48 h, the Mg-9.55Gd-2.27Y-1.28Zn-0.55Zr-0.11Nd alloy exhibited favorable comprehensive mechanical properties at room temperature: ultimate tensile strength (UTS) of 383 MPa, tensile yield strength (TYS) of 269 MPa, and fracture elongation (EL) of 5.1%.

Controlling hydration of hydratable alumina via co‐grinding with Mg–Al hydrotalcite

AbstractThe on‐site industrial application of hydratable alumina (HA)‐bonded castables is inhibited by the high hydration rate of HA. In this study, the hydration behavior of HA co‐ground with sheetlike Mg–Al hydrotalcite (MAT) is investigated. The properties of castables bonded with MAT‐bearing HA are systematically assessed. The hydration rate of HA co‐ground MAT decreases as this allows MAT sheets to be effectively inserted into the microcracks of HA particles during grinding, thus decreasing the direct contact area between HA and water. The strength of MAT‐bearing castables (0.5 and 1 wt%) fired at 800°C improved slightly owning to the generation of magnesia–alumina spinel. The mechanical strength of castables fired at 1100 and 1550°C decreased as the MAT content increased owing to an increase in porosity. Based on an analysis of the hydration behavior of HA and the properties of HA‐bonded castables, the optimal MAT/HA weight ratio is approximately 1/10.

Effects of Proportion of BF3-MEA on Curing Properties of AG-80/DDS Resin System

Through differential scanning calorimeter (DSC), the systematic analysis is carried out on the issues including: the curing properties of the resin system composed of 4,4’-diaminodiphenylmethane epoxy resin (AG-80), 4,4’-diaminodiphenylsulfone (DDS) and boron trifluoride monoethylamine complex (BF3-MEA); the effect imposed by the varying content of BF3-MEA on the temperature, extent and rate of reaction; and the effect imposed by the varying DSC heating rates on the curing properties of the AG-80/DDS/BF3-MEA resin system. In the meantime, Ti0, Tp0 and Tf0 are derived, and the curing regimes of the three proportioning schemes are determined accordingly. The gel time of the AG-80/DDS/BF3-MEA resin system is measured through the gel drawing method, and the effect of the BF3-MEA content on the gel time is assessed, so as to determine that 0.7 times of the gel time shall be the pressure time for the forming of composite materials. Furthermore, tests are carried out on the mechanical properties of the resin cast and the carbon fiber composite materials prepared through the three proportioning schemes. The results have shown that when the content of BF3-MEA is 2%, the AG-80/DDS/BF3-MEA resin system outperforms the other proportioning schemes in terms of the curing process and the processability of its composite materials. Besides, the comprehensive mechanical properties of the resin cast and the carbon fiber composite are better.

Strength and ductility enhancement of twin-roll cast Al-Zn-Mg-Cu alloys with high solidification intervals through a synergistic segregation-controlling strategy

Center segregation and banded intergranular segregation (B-IGS) should be well controlled to improve the mechanical properties of twin-roll cast (TRC) aluminum alloys, especially for alloys with high solidification intervals. In the present work, a synergistic grain refinement strategy was designed using an Al-5Ti-B grain refiner and Ti, Zr, and Sc microalloying elements to simultaneously control center segregation and B-IGS in TRC Al-Zn-Mg-Cu alloys. As the grain size decreased, center segregation defects were eliminated and transformed into dispersed B-IGS defects; simultaneously, the width and length of the B-IGS were also reduced. Moreover, the macro-distributions of the alloying elements along the thickness direction became more homogeneous due to a weak shear-induced dilation effect. The well-controlled multiscale segregation improved the uniformity of the alloy macrostructure, accelerated the redissolution of the crystalline phase, dispersed the aggregated residual phase, and refined grains under the T6 state. Hence, the strength and ductility of the alloys under the T6 state were simultaneously improved, and the hardness distribution along the thickness direction became more homogenous. Furthermore, the underlying mechanisms of segregation evolution and strength and ductility enhancements were elucidated. This work provides a novel strategy to effectively control multiscale segregation and produce high-performance aluminum alloys with high solidification intervals by TRC.

Effect of Zn Addition on the Microstructure, Mechanical Properties, and Fracture Behavior of As-Cast Mg-Gd-Y-Zr Alloys

The microstructure and mechanical properties of semi-continuous casting Mg-Gd-Y-Zr magnesium alloys with different Zn contents were studied in this paper. The results showed that an increase in Zn content resulted in gradual refinement of the grains and a gradual increase in the volume fraction of the second phase. At a Zn content of 0.7 wt%, the microstructure was mainly composed of the α-Mg matrix and the Mg5(GdY) and long-period stacking order (LPSO) phases. An increase in the Zn content lowered the volume fraction of the Mg5(GdY) phase and increased the volume fraction of the LPSO phase. At a Zn content of 3.3 wt%, the microstructure was mainly composed of the α-Mg matrix and the LPSO phase. Among these alloys, the alloy without Zn addition showed an optimal ultimate tensile strength and yield strength of 229 MPa and 185 MPa, respectively, while the alloy with 3.3 wt% Zn showed an excellent elongation after fracture of 4.5%. The tensile fracture analysis indicated that the cracks of the alloy without Zn mainly originated at the trigeminal junction of the grain boundary, the cracks of the 0.7 wt% Zn and 1.5 wt% Zn alloy mainly originated at the interface of the Mg/lamellar LPSO phase, and the cracks of the 3.3 wt% Zn alloy mainly originated at the bulk LPSO phase of the grain boundary and then propagated along the bulk LPSO phase.

Microstructure and Mechanical Properties of Cast Al-Si-Cu-Mg-Ni-Cr Alloys: Effects of Time and Temperature on Two-Stage Solution Treatment and Ageing

Ameliorating the high-temperature performance of cast Al-Si alloys used as engine components is essential. The effects of different T6 heat-treatment processes on the microstructure and mechanical properties of cast Al-Si-Cu-Mg-Ni-Cr alloys were investigated in the present study. The results demonstrate that, under the optimal solution treatment conditions of 500 °C for 2 h and 540 °C for 4 h, the T-Al9FeNi phase was present in the alloy, and the roundness of primary Si and the aspect ratio of eutectic Si in the alloy reached valley values of 1.46 and 2.56, respectively. With increasing ageing time at 180 °C, the tensile strength significantly improved, while the microhardness first increased and then decreased. When the ageing time was 4 h, microhardness reached a peak value of 155.82 HV. The fracture characteristics changed from quasi-cleavage to the coexistence of quasi-cleavage and dimples. After heat treatment, the high-temperature tensile properties of the alloy improved, which is a significant advantage compared to the as-cast alloy. The stable Al3Ni and Al9FeNi phases inhibited the cracking of the alloy at 350 °C.

Fabrication of Aluminium Hybrid Metal Matrix Composite Reinforced with Silicon Carbide and Graphite by Stir Casting Method

The AA2014/SiC/Gr hybrid metal matrix composites are developed with addition of 0.5% to 1.5% SiC particles (weight fraction) in 0.5% weight fraction interval and the graphite (Gr) is 1% weight fraction constant for all composites were prepared by stir casting method. The effects of SiC and Gr on the microstructural and mechanical properties of the base cast and hybrid composites were studied by SEM, hardness, and impact tests. The results indicate that mechanical properties of the aluminium hybrid metal matrix composites (AHMMCs) change according to their increment of SiC and Gr particle. The hardness and impact strength of base cast and hybrid composites increased during the addition of SiC and Gr particle. The hardness and impact strength of base cast and hybrid composites increased during the addition of SiC and Gr particle. The maximum hardness is observed in the fourth sample with 1% Gr and 1.5% SiC with 7% increment which is 102.4 VHN. The high impact strength was observed for base alloy of 24% than hybrid composite. The composite of 1% SiC and 1% Gr is given less wear loss and coefficient of friction. The Corrosion resistance is better in the composite of 0.5% SiC and 1% Gr and the optical micrographs shows that the composite with 0.5% SiC and 1% Gr shows good texture.

Enhanced long-term thermal stability and mechanical properties of twin-roll cast Al–Mg–Si alloys with Mn and Cu additions

The long-term thermal stability of Al–Mg–Si alloy is of great significance for its engineering application. In this work, the effects of Mn and Cu on the microstructure and mechanical properties of the twin-roll cast (TRC) AA6005 alloy after peak aging and long-term thermal exposure were studied. The results show that the addition of Mn introduces Al(FeMn)Si dispersoids, which improves the mechanical properties of the alloy under the peak aging condition by dispersion strengthening. After thermal exposure at 150 °C for 1000 h, the Al(FeMn)Si dispersoids have good thermal stability while do not significantly improve the mechanical properties. The reason may be related to the decreased number density of the β″ phase after alloying with Mn. The addition of Cu changes the aging precipitation sequence, and the needle-like pre-Q′ phase is formed during artificial aging. Moreover, due to the low diffusion rate of Cu in the Al matrix, Cu atoms can better stabilize the structure and then improve the coarsening resistance of the precipitates, and therefore the Cu-containing precipitates exhibit better thermal stability than the β″ phase. After thermal exposure at 150 °C for 1000 h, the yield strength of the 0.5Cu alloy decreases by only ∼12 MPa (from ∼295 to ∼283 MPa), which is significantly lower than that of the AA6005 alloy (∼41 MPa, from ∼274 to ∼233 MPa). The yield strength of the 0.25Mn0.25Cu alloy decreases by ∼27 MPa (from ∼294 to ∼267 MPa) and is more suitable for industrial production as its composition is within the range of commercial 6xxx aluminum alloys. The results would provide a strategy for the preparation of Al–Mg–Si alloys with high thermal stability.

Binder Jet Additive Manufacturing Process and Material Characterization for High Temperature Heat Exchangers Used in Concentrated Solar Power Applications

The U.S. Department of Energy’s (DOE) Sunshot 2030 initiative has a goal of reducing the cost of concentrating solar power (CSP) to 5 cents per kWh for baseload power plants. One of the potential pathways to this goal includes a reduction in the cost of the supercritical CO2 (sCO2) power block to 0.9 cents per kWh. Recuperators—high and low temperatures, used in the sCO2 power cycle, contribute to >50% of the cost of the power cycle. This work studies the feasibility towards a ≥10% cost reduction for High Temperature Recuperators (HTR) used in the sCO2 power cycle. One way to address the cost reduction is by leveraging low-cost additive manufacturing, specifically, Binder Jet Additive Manufacturing (BJAM) to 3D print HTRs at scale. This study focuses on the development of a BJAM process towards 3D printing HTR cores using Stainless Steel alloy 316L (SS316L). To evaluate the suitability of the BJ process towards the HTR, high level specifications of the application are translated to materials capability requirements. Subsequently, at-temperature materials testing is conducted on as-printed and sintered additively manufactured coupons. Data from the coupons are compared against cast and wrought SS316L data obtained from the literature. Results show that the tensile properties from the BJ process compare well against cast properties. Furthermore, a baseline analysis of creep testing data is established for the BJ process, and insights are drawn from the results towards future improvements of the process.

On the Effectiveness of Rotary Degassing of Recycled Al-Si Alloy Melts: The Effect on Melt Quality and Energy Consumption for Melt Preparation

The effectiveness of rotary degassing on the defect formation and mechanical properties of the final casting of aluminium alloy EN AC 46000 was investigated, along with its impact on the energy consumption in the casting furnace. In the melt preparation prior to casting, the molten metal is usually transported from the melting furnace to the casting furnace with rotary degassing as a cleaning procedure. Under the conditions of this specific study, negligible degradation was observed in the mechanical properties of the final cast component in an aluminium EN AC 46000 alloy after removing the rotary degassing step in the process. Furthermore, removing the rotary degassing step led to a reduced temperature drop in the melt, thus minimizing the need for reheating (energy consumption) by up to 75% in the casting furnace. The reduced energy consumption was up to 124,000 kWh in yearly production in a 1500 kg casting furnace. The environmental impact showed a ~1500 kg reduction in CO2 for one 1500 kg electrical casting furnace in a year.

Microstructure and properties of a novel cost-effective FeNi-based eutectic high entropy alloys

Eutectic high-entropy alloys (EHEAs) are becoming a new research focus in the field of metal materials due to the outstanding casting properties, high fracture strength and high tensile ductility. In present study, a series of [FeNi]75-xCr15Mn10Nbx (x = 0, 3, 6, 9, 10, 12, 15, x value in molar ratio) Co-free high entropy alloys were fabricated and evaluated to investigate the alloying effect of Nb on microstructure and compression properties. With the addition of Nb, the microstructure changes from monophase to divorced eutectic with primary FCC phase and then to the hypoeutectic. With the further addition of Nb, the microstructure is almost eutectic (irregular eutectic + regular eutectic), and then transformed into hypereutectic with primary Laves phase. The compressive fracture strength of [FeNi]75-xCr15Mn10Nbx first increases and then decreases accompanied by the degradation of compressibility as the addition of Nb. The eutectic alloy [FeNi]65Cr15Mn10Nb10 exhibited comprehensive mechanical properties with compressive fracture strength 1638 MPa and fracture strain 22%. The strengthening mechanism of the HEAs is mainly fine grain strengthening (Hall-Petch) and Laves phase strengthening, supplemented by FCC solid solution strengthening. The microstructure formation is explained by Md criterion, when Md is less than or equal to 0.89, the microstructure is composed of single FCC phase; when Md is greater than 0.89, the microstructures are composed of FCC + Laves phases.