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The flow forming process is widely used in the production of axisymmetric industrial parts. The advantage of the flow forming process over other manufacturing methods is the use of simple tooling, reduced forming loads due to localized deformation, and enhanced mechanical properties and surface quality of finished parts. In this research, the warm flow forming process of AA6061-O aluminum alloy has been investigated for the first time. For this purpose, laboratory equipment and samples were designed and fabricated. In this study, the effect of temperature, thickness reduction, and number of passes (number of forming steps) on dimensional accuracy (thickness variation) and mechanical properties of warm flow formed AA6061-O alloys pipes have been experimentally investigated. The experimental results show that flow forming increases the strength and decreases the ductility of the formed pipe at all process levels compared to the initial non-flow forming pipe. However, the ductility of the pipe increases and its strength and microhardness decrease by increasing the forming temperature from 20 to 300 ° C. While with increasing the percentage of thickness reduction from 20% to 60% at a constant forming temperature, the strength and micro-hardness of the warm flow-formed pipe increases and its ductility decreases.

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Flow forming is one of the advanced methods for producing low thickness cylindrical parts. The dimensional accuracy of pipes produced by the flow forming method is much higher than other methods and this method is widely used in the aerospace industry. In this research, the effect of number flow forming passes has been investigated on the mechanical properties and microstructure of AISI4130 steel. Three stages of thickness reduction have been successfully completed and in the fourth stage, the tube was fractured. In the first stage of this pass, the desired steel thickness has changed from 14.2 mm to 9.3 mm. In the second stage, the thickness reached 2.6 mm, in the third stage to a thickness of 2.3 mm and in the fourth stage by reaching 1.8 mm thick, there has been a tear in the pipe. During the flow forming process, the maximum amount of 84.5% thickness reduction can be achieved. To achieve a higher percentage of thickness reduction, it is necessary to re-anneal the flow formed sample. To investigate the tensile properties, tensile tests have been done through both longitudinal and circumferential directions. According to the results, it was found that the flow forming operation on this steel has increased the hardness and yield, and ultimate strength of the material at every stage. Also, the hard work done at every stage on this steel by maintaining the ferritic pearlite-ferritic structure has caused finer grain structure and elongation of the grains.