Al-cu Solder Vacuum Brazing Pure Aluminum Of Cu Diffusion Behavior

The Al-Cu rapid-solidifying solder ribbons are prepared by the method of rapid solidification and the ordinary Al-Cu solder ribbons are casted. Two kinds of solder ribbons are studied thoroughly by the method of DTA, SEM, X-ray, and so on. The research shows that the elements of the rapid-solidifying solder ribbons have homogeneous structure and very small crystal grain size and the ordinary Al-Cu solder ribbons have crystal segregation and pine-tree crystal. Because of the high interface energy of the rapid rapid-solidifying solder ribbons of its small crystal grain size, its melting point is lower than ordinary Al-Cu brazing by 3. 0°C, and melting area is lower than ordinary Al-Cu solder by 1.2℃.When pure aluminum was soldered in vacuum environment with two kinds of solder ribbons at four kinds of working temperature (590℃, 600℃,610℃, 620℃) and in four kinds of heat-retaining periods (5min, 10min, 15min, 20min), the author analyzed the microstructure of the soldered joint and observed the phenomenon of diffusion of element copper. The mechanism of diffusion of element copper is put forward that element copper diffused preferentially in the crystal boundary of aluminum, and the depth and breadth increases as temperature of soldering is added and heat-retaining period of soldering is prolonged. The diffusion of Cu element takes place in the crystal grain and on the surface of the matrix of aluminum, but its intensity is very low. When the soldering temperature and soldering heat-retaining period is identical, the diffusibility of Cu in the rapid-solidifying solder is remarkably higher than that of the ordinary solder. Discrimination of diffusivity reduces with the increase of soldering temperature and prolonging of heat-retaining period.