Interfacial microstructure and properties of TC4/QCr0.8 joints brazed with AgCu filler

QCr0.8 alloy was brazed to TC4 by using AgCu filler metal in vacuum. The typical interfacial microstructure of TC4/AgCu/QCr0.8 brazed joint was TC4/CuTi+Cu3Ti2+CuTi2/Ag(s,s)+Cu4Ti/Ag(s,s) +Cu(s,s)/QCr0.8, which was determined by SEM, EDS, and XRD. The effects of brazing temperature and time on microstructure and mechanical property were studied. Results show that the amount of AgCu eutectic phase decreased while that of Ti-Cu compounds increased with brazing time and temperature increases. Shear strength of the joints exhibited rising firstly and then declining pattern as temperature rose, and the maximum shear strength of 449 MPa was obtained under the condition of 890 ℃/0 min. The growth of Ti-Cu compounds as brazing time extended deteriorated the property of the joint. As a result, the shear strength of the joints significantly declined with extended brazing time.