Search

Al7075-Cu composite joints were prepared by the squeeze overcast process. The effects of melt temperature, die temperature, and squeeze pressure on hardness and ultimate tensile strength (UTS) of squeeze overcast Al7075-Cu composite joints were studied. The experimental results depict that squeeze pressure is the most significant process parameter affecting the hardness and UTS. The optimal values of UTS (48 MPa) and hardness (76 HRB) are achieved at a melt temperature of 800 °C, a die temperature of 250 °C, and a squeeze pressure of 90 MPa. Scanning electron microscopy (SEM) shows that fractured surfaces show flatfaced morphology at the optimal experimental condition. Energy-dispersive spectroscopy (EDS) analysis depicts that the atomic weight percentage of Zn decreases with an increase in melt temperature and squeeze pressure. The optimal mechanical properties of the Al7075-Cu overcast joint were achieved at the Al2Cu eutectic phase due to the large number of copper atoms that dispersed into the aluminum melt during the solidification process and the formation of strong intermetallic bonds. Gray relational analysis integrated with the Taguchi method was used to develop an optimal set of control variables for multi-response parametric optimization. Confirmatory tests were performed to validate the effectiveness of the employed technique. The manufacturing of squeeze overcast Al7075-Cu composite joints at optimal process parameters delivers a great indication to acknowledge a new method for foundry practitioners to manufacture materials with superior mechanical properties. [ABSTRACT FROM AUTHOR]

With increasing demand of high strength to low weight ratio materials, aluminum alloys are getting more commercial importance. Investment casting process following by directional solidification has the capability to produce cast parts with minimum or no grain boundary. These cast parts can perform even at elevated temperatures with improved mechanical properties, especially creep. Owing to these embedded capabilities, directional solidification process is preferred over conventional casting procedures for aluminum alloys. Properties of directionally solidified components highly depend on input parameters. This research aimed to develop the mathematical models for the prediction of ultimate tensile strength (UTS), percentage elongation, and hardness of directionally solidified Al-4.3% Cu alloy. A series of experiments were performed to investigate the effects of grain selector parameters including spiral thickness, spiral diameter, spiral pitch, and spiral rotations using Box-Bhenken design. For the adequacy and validity of mathematical models, analysis of variance (ANOVA) and confirmation experiments were performed, respectively. Spiral thickness was observed as most effective parameter affecting UTS, percentage elongation, and hardness followed by spiral pitch and spiral diameter. Microstructural analysis reveals that grain boundaries disappeared at low level spiral thickness and pitch and high level of spiral diameter and rotations. In comparison with base metal, percentage improvement in UTS, percentage elongation, and hardness ranging from 37.5~93.9%, 20.5~81.3%, and 37.6~85.3%, respectively, has been observed. Innovation in this research is the mathematical modeling of mechanical properties for Al-4.3% Cu alloy using directional solidification process. [ABSTRACT FROM AUTHOR]

The current study aims to investigate the effects of process parameters on mechanical and microstructural characteristics of Al 6061-SiC composite fabricated via squeeze casting. Seventeen experiments in total have been conducted according to Box-Behnken experimental design which contained three process parameters (squeeze pressure, melt temperature, and SiC wt.%) while recording the responses including ultimate tensile strength, hardness, and percentage elongation. ANOVA (analysis of variance) was employed to evaluate the significance and prediction capability of mathematical models developed through regression analysis. The results indicate that squeeze pressure, melt temperature, and SiC wt.% significantly affect the responses whereas ductility is drastically reduced at higher concentrations of SiC reinforcement. SEM micrographs of failed test specimen have been found to be indicative of ductile fracture at higher levels of squeeze pressure and melt temperature. The multi-objective optimization problem has been transformed to an equivalent single-objective problem using grey relation analysis. The desirability analysis revealed optimum setting of process parameters which was confirmed to have improved the ultimate tensile strength by 1.61%, hardness by 1.56%, and percentage elongation by 11.11% as compared to the initial setting. [ABSTRACT FROM AUTHOR]

The present study aims to optimise the process variables which are involved in the fabrication of Al 6063-SiC composite by squeeze casting process. The variables included squeeze pressure, melt temperature and silicon carbide (SiC) reinforcement. The effects of these variables on ultimate tensile strength and hardness were studied with the help of nine experiments. The analysis of variance confirmed the significance of the process variables. The optimal combination of process variables to maximise the ultimate tensile strength and hardness is achieved as 120 MPa (17.4 ksi) squeeze pressure, 850°C (1562°F) melt temperature and 15 weight percentage SiC reinforcement. The confirmatory test indicated the effectiveness of the employed technique to optimise the squeeze casting process variables for the development of aluminium matrix composites. [ABSTRACT FROM AUTHOR]

This research aims to investigate the effects of as-casted and proposed in situ heat-treated squeeze casting of Al-3.5 % Cu alloy. The effects of squeeze pressure, melt temperature and die temperature on ultimate tensile strength, percentage elongation and hardness were modelled and analysed for as-casted and in situ heat-treated squeeze casting using the Box-Behnken design. Response surface methodology was used for experimental design, empirical modelling and analysis. Adequacy and validation of the developed models were verified using ANOVA and confirmation experiments, respectively. The results revealed squeeze pressure as the most significant input variable followed by die temperature under as-casted and in situ heat-treated squeeze casting conditions. The comparative analysis suggested in situ heat-treated squeeze casting conditions as the best alternative which resulted in 7.9~11, 6.7~25.7, and 2.2~7.7 % improvement for ultimate tensile strength, percentage elongation and hardness, respectively. A considerable increase in mechanical properties provided a great evidence to reveal a new technique for foundry men to enhance the quality of squeeze casted Al-Cu alloys. Furthermore, the empirical model will aid practitioners to predict the desired mechanical properties prior to examination. [ABSTRACT FROM AUTHOR]

Gas tungsten arc welding (GTAW) is considered a well-established process in the manufacturing industry. Despite, certain challenges associated with high hardness of heat affected zone and cold cracking susceptibility of joints, are the main barriers for this process to be implemented successfully within high integrity structure. By using a combined procedure of experiments and modelling (response surface methodology (RSM) and multi-objective optimization: multi-objective genetic algorithm (MOGA)) allows obtaining good enhancement over uniform heating, cooling and the heat-affected zone which enable major progress in obtaining high quality welded parts. Therefore, this research study combines the experiments and modelling in a systematic manner considering for the first type the pre-heated treatment and without- pre-heating conditions of GTAW manufacturing. It leads to optimizing the process parameters of GTAW when manufacturing AISI 1045 medium carbon steel. The effects of critical parameters i.e. welding current: W C , welding speed: W S , and gas flow rate: G FR on the mechanical properties (ultimate tensile strength (UTS) and hardness) were investigated and evaluated against the microstructure of weld fracture. The multi-objective genetic algorithm corroborated with experimental observation enables to obtain a maximum UTS of approx. 625 MPa and hardness of 80.19 HRB for preheat condition. The results highlight an improvement in UTS of 0.2%–6.7% and a decrease in hardness of 0.1%–21.5% by implementing the preheating condition. • Assessment of mechanical attributes of Gas Tungsten Arc Welding was conducted for pre-heated and non-pre-heated conditions. • Details of the microstructure, ultimate tensile strength, and hardness of joints are revealed. • Empirical modelling and parametric optimization was corroborated with Multiobjective Optimization Genetic Algorithm (MOGA). [ABSTRACT FROM AUTHOR]