This study aims to determine the effect of high temperature on the fatigue life of AA7075-Al2O3 nanocomposites (6 wt % Al2O3) fabricated by stir casting. The research problem is to determine the durability, fatigue resistance, and mechanical properties of the nanocomposite under constant and variable loading conditions at elevated temperatures, as well as to identify changes in its behavior due to exposure to high temperatures. The results show that higher temperatures have a big effect on the nanocomposite's fatigue performance under both loading conditions. When the material was tested at a high temperature (150 °C) with an extra 6 wt % Al2O3, the ultimate tensile strength and yield stress both went up by 16 % and 15.7 %, respectively. Its fatigue life was also successfully tested under both variable and constant amplitude load conditions. The interpretation of the results suggests that the changes in the microstructure of the nanocomposite material at elevated temperatures lead to an increase in dislocation density and grain size, resulting in an improvement in its mechanical properties. The findings can be utilized to optimize the nanocomposite fabrication process and enhance its fatigue resistance at high temperatures. In addition, the results can be used to enhance the design of aerospace components and high-temperature engines that require materials with excellent fatigue resistance at elevated temperatures. In summary, the investigation of the effect of high temperature on the constant and variable fatigue lives of AA7075-Al2O3 nanocomposite provides valuable insight into the material's mechanical properties. The findings contribute to the development of materials that can withstand high-temperature conditions, which has implications for a variety of industries.

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Purpose: The present work aims to investigate the influence of CO2 laser spot welding (LSW) parameters on welding profile and mechanical properties of lap joint of AISI 321 thin sheet metals, and analyze the welding profile numerically by finite element (FE) method. Design/methodology/approach: The weld carried out using 150 W CO2 continues wave laser system. The impact of exposure time and laser power on the welding profile was investigated using an optical microscope. Microhardness and tensile strength tests were used to evaluate the mechanical properties of the joint. Ansys software was utilized to simulate the welding profile numerically. Findings: The results revealed that 2 s exposure time and 50 W power have led to uniform welding profile and highest shear force (340 N), lower hardness gradient across the heat affected zone (HAZ) and fusion zone (FZ). Finite element (FE) analysis of the welding profile showed good agreement with experimental analysis. Research limitations/implications: The selection of laser spot welding parameters for thin sheet metal was critical due to the probability of metal vaporisation with extra heat input during welding. Practical implications: Laser welding of AISI 321 steel is used in multiple industrial sectors such as power plants, petroleum refinement stations, pharmaceutical industry, and households. Thus, selecting the best welding parameters ensures high-quality joint. Originality/value: The use of CO2 laser in continuous wave (CW) mode instead of pulse mode for spot welding of thin sheet metal of AISI 321 austenitic stainless steel consider a real challenge because of the difficulty of control the heat input via proper selection of the welding parameters in order to not burn the processed target. Besides, the maintenance is easier and operation cost is lower in continuous CO2 than pulse mode.