Study On The Heat Treatment Process Of Brazing-thin Aluminum Alloy Bar-plate Radiator

In order to meet the light-weight and high-strength requirements of aluminum alloy bar-plate radiators, this paper is based on the practice of enterprise production and the research of experimental theory for the main target of 30% reduction in radiator weight to make a study on materials selection, vacuum brazing and heat-treatment process of radiators, which can provide related theoretical research and production foundation to develop new-type radiators for enterprises, the purpose is to strengthen enterprise competitions and market shares.The results show that: In the vacuum brazing process of 608℃/70 min, the aluminum alloy weld presents less defects of crack, dissolution, pore, and a lot of primary phase precipitates are existed in the weld microstructure; Grain-sizes of base-materials perform a certain degree of growing-up and mechanical properties of welds appear severe softened after brazing; With the change of solution temperature and time, solid solubilities of primary phase and grain sizes in the welds microstructure make a big difference and even some grains are able to cross through welds, it is easy to make welds microstructure burnt, grain-sizes excessive growing-up and grain-boundary melted in solution temperature of 570℃, the appropriate solution process of welds is 530℃/3h; There are lots of similar dimples in shape, size, and depth existed on the fracture of original welds, however, more tearing-ridges and cleavage-planes are emerged on the fracture after welds experienced solution-aging process of 530℃/3h, the fracture not only performs the brittle fracture feature based on a main mechanism of cleavage-fracture, but also a certain degree of ductile fracture feature. In the aging treatment of 150℃, many black particle precipitates are appeared in the weld microstructure for 1h, which show different sizes but distributed uniformly, however, particle precipitates further perform more fine and distribution for 5h, but present excessive thick and low density for 9h, the suitable aging process for welds is 150℃/5h; With the change of solution temperature and time, the density of primary phase precipitates in base-metal microstructure is to decrease gradually, sizes of grain are to increase evenly, there are melting pellets appeared in local grain-boundary of base-metals when solution temperature is 570℃, the appropriate solution process of base-metals is 550℃/5h; When base-metals are in the aging treatment of 150℃, the microstructure does not appear obvious precipitated phase for 1h, lots of needle-shape β″and rod-shape β′ phase are presented for 9h, the sheet-shape β phase is precipitated for 17 h, the suitable aging process for base-metals is 150℃/9h. In order to ensure the strength of welds and base-metals, the optimal heat-treatment process of radiators is 540℃/4h solution and 150℃/6h aging treatment.