Investigation Of Semi-Solid Welding Of SiCp/6061Al Composites

SiC_p/6061Al composites are a kind of composites with 6061 alloy matrix and SiC particulate reinforcements. Because of their outstanding performances, they will be widely applied and even replace some traditional metallic materials. As SiC_p/6061Al composites are heterogeneous multi-component materials, theirs welding characteristics are very complex. So far, their welding problem eliminates their rapid developing and makes it one of research focuses in the world. In the present paper, a new welding method of particle reinforced aluminum matrix composites based on semi-solid bonding technique has been suggested. The composite billets are heated up to the solid-liquid mixing two-phase state and then held for certain time. Compact forces are then employed onto the heated billets and perfect joints will be obtained via thixotropic forming.It can be shown that the temperature is the key parameter of semisolid welding. At the higher temperature, the deforming of sample will becomes bigger and the particle aggregation will be more serious. When the temperature surpasses a critical value, the interface reactions will be activated. And the higher the temperature is, the more violent the reaction will be. And 620℃is the suitable temperature of welding of SiC_p/6061Al composite, and there is little particle aggregation under this temperature,. Well-jointed SiC_p/6061Al composite sample can be obtained with 20N impact force at 620℃for 5min. And the tensile strength of joint can be up to 67.8% of the composite billet. The oxidation of the composite surface is one of the important elements which affect the semi-solid welding result. The existence of oxide film will significantly influence the metallurgy and diffusion processes. However, the oxide film will eventually broken as the welding temperature increases. There is no apparent reaction between Al matrix and SiC particles and little fragile phase is found in the weld joint. As an impact force has been employed during the semi-solid welding process and the solidification shrinkage of the composite is small as the matrix alloy is at solid-liquid state, there is no apparent draw or shrinkage in the joint zone.