Application Of Cu-based Amorphous To Transient Liquid Phase Bonding Of Metals As Interlayer

Transient Liquid Phase Diffusion Bonding （TLP） has many advantages, such as shortconnection time, low bonding temperature, easy to operate, small residual stress and heataffected zone. It becomes a research hotspot in the current welding field and has uniqueadvantage, especially for the welding of dissimilar materials. For Amorphous alloys, thecompositions are usually close to the eutectic point, and thus the eutectic structure is easyto form during solidification. Moreover, the amorphous alloy melting point is usuallymuch lower than that of crystalline alloys. So, amorphous alloys are the best choice to beinterlayer of TLP bonding. In the present thesis, a Cu-based amorphous alloy was firstlyprepared by copper mold suction casting method, and the thermodynamic properties andthe atom diffusion behavior at high temperatures were investigated. On this basis, takingthe amorphous alloy as the interlayer, pure Cu was bonded with pure Cu and pure Fe byusing TLP method, and the effects of the bonding temperature and time on the interfacemicrostructure and the mechanical properties of the joints were investigated. The mainresults are as follows:（1） By using copper mold suction casting method, a Cu-base amorphous alloyCu₄₆Zr₄₆A_l8was successfully prepared. The amorphous alloy shows an amorphous glasstransition temperature T_gof425℃and a crystallization temperature of500℃. The widthof the supercooled liquid region is75℃and the melting point of the alloy is about720-860℃;（2） At the temperatures ranging from440℃to485℃, Cu atom diffuses in theamorphous alloy in the polyatomic collaboration mechanism, and it can be described bythe Arrhenius equation. The diffusion activation is518kJ/mol. In comparison with thecrystalline alloys, Cu atoms diffuse more difficulty in the amorphous, which is related tothe special atomic structure of the amorphous alloys;（3） By using Cu₄₆Zr₄₆A_l8amorphous alloy foil as interlayer, pure copper wassuccessfully joined with pure Cu through TLP bonding method. It is found that, with theincreasing of the bonding temperature, the mechanical property of the bonding joint canbe improved obviously. Under welding conditions of90℃0/120s/0.5M Pa, themicrostructure of the bond consists of the eutectic structure. The microhardness of thejoint is close to the base metal and the joint exhibits a high tensile strength of345.0MPa;（4） By using Cu₄₆Zr₄₆A_l8amorphous alloys as the interlayer, pure Cu was successfully bonded with pure Fe through TLP bonding method. The microstructure andmechanical properties of the joints are strongly dependent on the temperature and holdingtime. It is founded that, the microstructure of the bond changes from intermetalliccompounds to eutectic as the bonding temperature increases from700℃to900℃, and themechanical properties of the joints are promoted. On the other hand, as the holding timeincreases, the weld width increases significantly without changing the mechanicalproperties of the joints. The joints fracture in the brittle mode. This is because that a layerof brittle intermetallic compounds of ZrFe₂（Cu） forms at interface between Fe matrix andthe interlayer, in which, crack is easy to initiate and expand rapidly, resulting in the brittlefracture.