Effect of CNTs on microstructure and mechanical properties of TC4 and C/C composites brazed joint

Abstract

TC4 titanium alloy was brazed to C/C composite by using AgCu4.5Ti+ xCNTs (x represents weight content, %) composite filler with CNTs added (Herein after referred to as AgCuTiC composite filler) metal in vacuum. With the CNTs content was 0.2%, under the condition of 880 ℃/20 min, the typical interfacial microstructure of the brazed joint was TC4/diffusion layer/Ti2Cu/TiCu/Ti3Cu4/TiCu4/TiC+TiCu2+Ag(s.s)+Cu(s.s)/Ti3Cu4/TiCu4/TiC/C/C composites, which was determined by SEM and EDS. The effect of CNTs content on the microstructure and properties of the joint was investigated. The results indicated that with the increase of CNTs content, the width of the brazed joint decreased, the interfacial microstructure refined, the content of brittle Ti3Cu4 and TiCu4 compounds in the interface decreased, the content of TiC and TiCu2 compounds increased,the shear strength of the joint show a trend of increasing first and then decreasing. The maximal shear strength of 44 MPa was obtained with the CNTs content was 0.2%. With the addition of CNTs, the interfacial microstructure can be refined, the residual stress caused by mismatch of the thermal expansion coefficient between the central area of the joint and the substrate materials on both sides can be released, which improves the shear strength of the joint effectively.