| Friction Stir Additive Manufacturing(FSAM)has solved most of the inherent defects of molten metal-based additive manufacturing and has unique advantages in light alloy additives.However,the existing solid state friction stir additive manufacturing technology has the problems of easy contamination of particles,low additive efficiency,and low material utilization,etc.,which makes friction stir additive manufacturing difficult in engineering applications.Therefore,this article uses the technology of friction stir welding and additive manufacturing to develop a friction stir additive manufacturing technology without lateral shoulder.This article selects the laterally stirred friction additive manufacturing of 6156-T6 aluminum alloy as the research object,and independently designs an additive tool suitable for laterally stirred friction additive manufacturing,and selects and optimizes the process parameters in the additive process.Explore,expound the characteristics of the lateral FSAM process flow,reveal the impact of process parameters on the surface forming in the additive zone;determine the optimal process parameters through appearance molding and internal macro molding,and systematically compare the lateral direction under different process parameters.The difference between the macro-microstructure and mechanical properties of the FSAM additive zone;by measuring the temperature changes in the lateral FSAM additive process and correlating the changes in the microstructure performance of the additive zone,the energy and heat input characteristics and heat input pairs at different stages are revealed The impact of structural properties in the additive zone.The lateral FSAM additive tool designed and manufactured is used for additive manufacturing.In order to ensure the heat input of the lateral FSAM,the additive tool needs to be performed at a speed above 600 r/min.At the same time,before the overall test,parameters such as the inclination of the additive tool,the amount of depression,and the material of the backing plate need to be determined.The correlation between the process parameters and the surface forming and mechanical properties of the additive zone was studied.Only by selecting the appropriate process parameters can an additive zone with beautiful surface molding and excellent mechanical properties be achieved,and high-quality side-mixing friction additive manufacturing achieved..The mechanical properties of the additive zone were evaluated by tensile tests.The tensile results show that the lateral FSAM additive tool is used for the test.When the tool rotation speed is constant,the tensile strength of the additive zone increases first and then decreases with the increase of the traveling speed.When the traveling speed of the additive tool is unchanged,The tensile strength of the additive zone increases first and then decreases as the speed of the additive tool increases.The study found that when the tool speed is 950r/min and the travel speed is 37.5mm/min,the tensile strength of the stable additive zone reaches a maximum of 200MPa,and the elongation reaches 25%,which is much higher than the base material of the additive bar.According to the characteristics of the metallographic structure,the overall macroscopic metallographic structure of the additive sample is divided into lateral stirring friction manufacturing additive area,additive-substrate bonding area and substrate area,where the fracture of the substrate area occurs at both ends of the gauge and the port The surface is smooth,the fracture in the bonding zone is in the gauge distance and is jagged,and the fracture in the stable additive zone is in the gauge distance and the necking is obvious.Collected the temperature data in the process of laterally stirred friction additive manufacturing,clarified the characteristics of heat input and temperature curve during additive molding at different speeds and travel speeds in the process window,and revealed the heat input/thermal cycle.The relationship between microstructure evolution and performance of side-stirred friction additive manufacturing.Through the analysis of the overall temperature measurement test data,it can be found that the temperature curve in the lateral FSAM additive manufacturing process is divided into five stages.Generally,there is a similar "platform"phenomenon between the cutting of the additive tool and the stage of stable additive molding.The temperature stops and disappears after continuing the feed.A temperature line was taken at the center point of the additive bar,and the one-dimensional temperature field on the line at different additive stages under different process parameters was measured.The measurement results were collated and the effects of various process parameters on the lateral FSAM temperature field were studied.Studies have shown that with the increase of the rotation speed of the additive tool,the heat input of the additive manufacturing increases,which causes the thermal cycle temperature peak in the additive manufacturing to increase and reduces the cooling rate,thereby increasing the grain size and reducing the micro hardness of the substrate region.The effect of additive travel speed on the lateral FSAM thermal cycle is opposite to the effect of tool speed.The cooling speed increases with the increase of the additive travel speed,and the grain size decreases accordingly.Higher thermal cycling during the additive manufacturing process reduces the tensile strength and yield strength of the substrate,but has a smaller effect on the tensile strength and yield strength of the stable additive zone.This article reveals the advantages of 6156 aluminum alloy with lateral friction stir additive manufacturing,hoping to lay the theoretical foundation and practical value for the research and application of lateral FSAM technology... |
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