| The SiCp/Al composite is a particle reinforced aluminum matrix composite composed of a reinforced phase SiC and an aluminum alloy matrix.It has excellent mechanical properties and is poorly joining due to the presence of reinforcing phase SiC particles.It is difficult to obtain an excellent joint by fusion welding.In order to explore the weldability of the new joint technology,friction stir joining for SiCp/Al composites,this paper studied the flow field simulation of the friction stir joining of SiCp/Al composites,joint performance and tool wear,etc.The results are as follows:(1)In order to provide guidance for the design of the tool,the flow field simulation of the joint material of the SiCp/Al composite friction stir joining process was carried out.Based on the computational fluid dynamics principle,the heat flow coupling model of the friction stir joining process was established and joining using FLUENT software.The three-dimensional flow field simulation of the process and the flow properties of the joints by different shapes of the tool were analyzed.The results showed that the tool with the concave annular shoulder and the threaded stirring pin shape made the joint material have better flow performance.(2)According to the results of flow field simulation,the tool was designed and fabricated,and the influence of different process parameters on joint performance was studied.Firstly,experimental was carried out to determine a reasonable range of process parameters,followed by orthogonal experiments of different process parameters,and macroscopic and microscopic analysis of the joints.The results showed that the SiC particles in the base metal were broken after being stirred.The SiC particles were finer and more dispersed in the joint.The tensile strength of the joint was basically the same as that of the base metal.The microhardness curve of the joint showed an inverted V shape.The SZ area had the highest microhardness value.(3)In order to improve the mechanical properties of the joint,the post-treatment study of the friction stir joining was carried out.Four kinds of post weld heat treatments were carried out on the joints,and the effects of different heat treatment processes on the mechanical properties of the joints were investigated.The results show that the joint strength after heat treatment is improved,and the tensile strength of the joints from four heat treatments increases from 32% to 51%,but the joint elongation decreased significantly.(4)In order to study the wear law of the tool,the experimental research on the wear of the tool was carried out.The effect of different process parameters on the wear of the tool was investigated by measuring the weight of the tool before and after each joining.The causes of the wear of the tool in different periods were analyzed,and the “quick stop experiment” was carried out on the tool.By analyzing the instantaneous interaction between the tool and the material during the joining process,it was found that there was a diffusion abrasion between the pin and the base metal. |
PDF Full Text Request