Effect Of Ge, Ni Elements On The Properties Of Al-Si-Cu Filler Metal

In this paper, the effects of alloying elements (such as Cu, Ge, Si, Ni and RE) on theproperties of filler metals have been investigated based on the orthogonal experiments.By changing the level of Cu, Ge, Si, Ni and RE, the filler metals’ melting point,corrosion property, spreading behavior and their shear strength of the brazed joints havebeen tested and measured. The microstructure and phase composition of filler metalswere analyzed with SEM, EDS and XRD. The results show that:Within the range of this subject, the melting temperature of the filler metals decreasessharply with the addition of copper and germanium. When the concentration of Cureaches to20wt%and Ge to15%respectively, the filler metals have the lowest meltingtemperature. However the addition of copper and germanium will weaken theirprocessing performance, which is the result of the increasing and gathering of the brittleintermetallic compounds of Al2Cu phase. Based on the electrochemical performance inNaCl neutral solution, the corrosion current density reaches the lowest level by adding10%copper and5%germanium separately, in other words, the filler metal has thelowest corrosion rate. Furthermore, the addition of the two elements has beneficialeffect on the spreading property.Compared with copper and germanium, the level changing of silicon, nickel and rareelements has little influence on the melting point. But the addition of silicon couldincrease the spreading area sharply. The results also indicate that the vacuum joints havethe highest strength when the silicon content is8.5%. The addition of nickel elementcould increase the processing property and could reduce the density of the brittleintermetallic Al2Cu. When the content of Ni is3%, the alloy has the best corrosionresistance. The addition of Re can refine the microstructure significantly and make thecorrosion current density decrease obviously. Compared with the joints without the Reelement, the joint strength could be up to76MPa which is increased by35%when thecontent of Re is0.3%.