Comparison of AgCuSn15 brazing fillers prepared by mechanical alloying and layer composite methods for vacuum brazing of Ni substrate: microstructure and mechanical properties analysis

In order to reduce the brazing temperature of Ag-based filler and simultaneously avoid the problem of difficult processing, AgCuSn15 brazing fillers prepared by mechanical alloying method (named MA-1) and layer composite method (named LC-2) were employed to vacuum braze Ni substrate. The microstructure and mechanical properties of Ni/Ni joints brazed using MA-1 and LC-2 were compared. The effects of brazing temperature and brazing time on the mechanical properties of joints brazed using MA-1 were studied. The results suggest that the microstructure of the joint brazed using MA-1 is Ni/(Ni, Cu) 3 Sn + (Cu, Ni) 6 Sn 5 /Ag(s, s)+Cu(s, s)/(Cu, Ni) 6 Sn 5 +(Ni, Cu) 3 Sn/Ni, and there are small cracks caused by Cu 6 Sn 5 phase in the joint. Due to the incomplete alloying of AgCu and Sn, the microstructure of joint brazed using LC-2 is Ni/(Cu, Ni) 6 Sn 5 +(Ni, Cu) 3 Sn/Ag(s, s)+Cu(s, s)+Ag-Cu eutectic/(Ni, Cu) 3 Sn +(Cu, Ni) 6 Sn 5 /Ni. The strength of the Ni/Ni joint brazed using MA-1 is highest (42.74 Mpa) at 680°C for 30 min. The strength of the Ni/Ni joint brazed using LC-2 under the same conditions is 24.86 Mpa.