Experimental Study Of Diffusion-solution Layer In The Alumian-based Liquid/solid Phase Interfaces

The transient liquid phase diffusion bonding has important position in industry. There aregreat differences between A1 and Cu, Ti, Ni in the way of physical and chemical properties,so it is difficult to connect them together. It is difficult to get a joint with satisfactoryperformance to adopt the traditional welding such as melt soldering, brazing, but the liquidphase diffusion bonding is an effective method to connect A1/Cu, Al/Ti and Al/Ni. This paperadopts "rivet method" to make solid/liquid diffusion couples of the A1/Cu, Al/Ti and Al/Ni,and analyzes the behavior about diffusion and solution in the phase interface. Diffusion andsolution will occur in a certain heat treatment temperature and time, forming thediffusion-solution layer in the phase interface. The properties of the diffusion-solution layerdecides the capability of welding joint in large extent. Therefore, it has become the importantcontent of the transient liquid phase diffusion bonding to study the structure, lumber, growingup rules and the forming mechanism of the diffusion-solution layer in the phase interface.Theexperimental study shows that the thickness and number of the diffusion-solution layer willincrease with the rising of heat treatment temperature and the prolonging of time. Theirrelation is index relation between thickness and temperature, and a parabola relation betweenthickness and time; The micro hardness of the diffusion-solution layer is different in differentheat treatment conditions (temperature, time); And each phase layer of the binary metallicsystem nucleated in sequence in certain heat treatment temperature.The results show that thediffusion-solution layer of the A1/Cu liquid-solid diffusion couple formed four kinds ofintermetallic compounds such as Cu₄Al₃, Cu₃Al₂, Cu₅Al₃, Cu3Al at the temperature 700℃for10min. The diffusion-solution layer of the Al/Ni liquid-solid diffusion couple got two kinds ofintermetallic compounds under different experimental conditions which are respectivelyNi₂Al₃, NiAl₃. The diffusion-solution layer of the Al/Ti liquid-solid diffusion couple onlygenerated TiAl₃ under different experimental conditions in the diffusion layer.At the sametime, the thesis analysis the precipitation sequence of each phase layer to combineexperimental phenomena and Miedema model. The connecting of dissimilar metals often gets brittle intermetallic compound, which weakens the joint performance, therefore, to study theformation and growing up mechanism of the brittle intermetallic compound (this paper calleddiffusion-solution layer) has the extremely vital significance for improving the jointperformance.