In this study, the microstructure and mechanical properties of dissimilar bonding of Ti-6Al-4V/AISI 304 stainless steel by transient liquid phase with pure copper interlayer and copper foil with carbon nanotube coating have been investigated. For this purpose, the samples were cut to the required dimensions and prepared. In the next step, multi-walled carbon nanotubes with different amounts of 0.5, 2 and 3 weight percent were coated by electrophoretic deposition on pure copper foil. Then, the samples prepared was placed in a stainless steel fixture and transferred to a vacuum furnace under vacuum 10-2 Pascals. Other parameters of this research include bonding time of 60 minutes and temperatures of 900, 950 and 1000 °C. In order to study the microstructure of the joint area more precisely, a scanning electron microscope equipped with energy separation analysis was used. Shear strength and microhardness tests were also performed to eva‎luate the mechanical properties of the joint. The results obtained from microstructural studies show that there are three regions that include isothermal solidification zone, Athermal solidification zone and the diffusion afected zone in all samples, which indicates that the bonding time is insufficient. Formation of titanium carbide (TiC) phase in bonding samples at 950 and 1000 °C in the presence of 2 and 3 weight percent of carbon nanotubes, formation of intermetallic compounds and eutectic compounds in all samples are other results of microstructure study. The shear strength test showed that in the samples without the presence of nanotubes, the shear strength decreased with increasing temperature. In the bonded samples, which contained carbon nanotubes, in all cases, more strength was obtained than the samples without nanotubes, this increase was on average 1.5 times. The highest strength was recorded 227 MPa, which belonged to the bond sample at a temperature of 900 °C with the presence of 0.5% by weight of the nanotube. Also, the lowest strength was obtained at 1000 °C without the presence of nanotubes, which is 102 MPa. Fracture images showed that the predominant type of failure in all samples was brittle fracture and there was no evidence of ductile fracture such as dimple on the structure. Fracture images showed that the predominant type of failure in all samples was brittle fracture and there was no evidence of ductile fracture such as dimple on the structure. X-ray diffraction patterns showed that the position of the peaks changed due to the addition of nanotubes to the samples, which indicates distortion and strain in the lattice, which facilitated and accelerated the penetration of the elements.

مرتضي شمعانيان اصفهاني،‌ عباس بهرامي

ابوذر طاهري زاده،‌ مهدي رفيعائي