为了深入研究铝真空钎焊机理,直接对钎焊动态过程加以观察和分析是理想的研究方法。试验表明,Al-Si-Mg 系钎料在真空中加热时,Mg 蒸发与加热温度、真空度有着密切关系,在500—580℃温度范围内Mg 大量蒸发。Mg 蒸气进入真空室,与氧化性气氛(O_2和H_2O)发生反应,起到净化介质作用;与氧化膜(Al_2O_3)作用,使其变质,生成多孔疏松的MgAl_1O_4。动态观察与分析清楚地表明,熔化钎焊合金在基体金属表面润湿过程中,存在着Mg 蒸气对表面膜的掘进作用。因此,在铝真空钎焊过程中,Mg 蒸气所起的本质作用也正是还原和掘进作用. In order to further study the mechanism of aluminum vacuum brazing, it is an ideal research method to directly observe and analyze the dynamic process of brazing. Experiments show that when the Al-Si-Mg brazing filler metal is heated in vacuum, Mg evaporation is closely related to the heating temperature and the degree of vacuum, and large amount of Mg is evaporated in the temperature range of 500-580 ° C. The Mg vapor enters the vacuum chamber and reacts with oxidizing atmospheres (O 2 and H 2 O) to act as a purifying medium. It interacts with the oxide film (Al 2 O 3) to degenerate to produce porous and loose MgAl 1 O 4. Dynamic observation and analysis made it clear that during the wetting process of the molten brazing alloy on the metal surface of the substrate, there was a driving effect of Mg vapor on the surface film. Therefore, the essential role played by the Mg vapor in the aluminum vacuum brazing process is also the reduction and driving effect.