Study On The Preparation And Application In The Welding Of Aluminum Alloys Of Mg-based Amorphous Ribbons

The amorphous ribbons of Mg₆₅Cu₂₄Al₁Y₁₀, Mg₆₅Cu₂₂Al₃Y₁₀and Mg₆₅Cu₂₀A₁₅Y₁₀ alloys of 5mm in width, 70～80μm in thickness, using some of the Al elements instead of the Cu elements of Mg₆₅Cu₂₅Y₁₀alloys, were prepared by vacuum melt spinning method. The structure and crystallization process while heating were studied by differential scanning calorimeter analysis (DSC)and X-ray diffraction analysis(XRD)respectively.The values of Tg, Tx, Tm and melting temperature for amorphous ribbons, which are parameters to describe the glass forming ability and are expressed only by temperature, were deduced from DSC curves.A welding experiment was performed using Al-based alloys ZL203 as base metal and the Mg₆₅Cu₂₄Al₁Y₁₀, Mg₆₅Cu₂₂Al₃Y₁₀ and Mg₆₅Cu₂₀Al₅Y₁₀ amorphous ribbons as interlayer between 480℃and 520℃under 0.5MPa pressure. Micro morphology and elements distribution of the brazed joints were analyzed through metallographic microscopy, SEM and EDS .The results were as following: the welding joint interfaces of Mg₆₅Cu₂₄Al₁Y₁₀ brazing alloy contained contact discontinuity and cavities. With the welding temperature increasing, the contact discontinuity and cavities were reducing. The welding joint was formed the effective bonding when the temperature was in 510℃. The welding joint interfaces of Mg_65Cu₂₂Al₃Y₁₀ and Mg₆₅Cu₂₀Al₅Y₁₀ brazing alloy were obtained without sheet inclusion, pore and unbonding. The width of welded seams were narrowing and straight with the temperature increasing. The element of Al diffused along the grain boundary of the substrate into welding line. A little Mg and Y diffused into the base metal. The element of Cu distributed homogeneously and there was no segregation in weld seam. It wan studied the mechanical properties of the welding joint by the electrical universal test machine. The results showed that: The tensile strength of two middle layer joint specimen of Mg₆₅Cu₂₂Al₃Y₁₀ and Mg₆₅Cu₂₀Al₅Y₁₀ brazing alloy the tensile strength sharply decreased after the fist rising with the temperature increasing. When the temperature is in 510℃, the two different joint specimens respectively reached the max tensile strength 1.8MPa and 56.7MPa. When the temperature went on increasing to 520℃, The tensile strength of joint specimens were sharply decreased to 17 MP and 19.1MPa. The main reason was that this temperature was close to the melting point of the substrate materials, under the pressure, causing the organization of bulk material loosing. So the tensile strength of joint specimens were sharply decreased. The best welding temperature of this experiment was 510℃. Under the insulation of 5-20 minutes, time had little affection on the strength of the welded joints specimen.