Research On Brazing Of Hydrogenated TC4 Titanium Alloy

In this paper, the mechanism and technology of brazing hydrogenated TC4 titanium alloys were been studied according to its characteristic using three diffenent filler metals.The microstructure of the joints was analyzed by means of SEM,EPMA,XRD. At the same time, shear strength test was examined for the joints.The optimum brazing parameters for different filler metals were given to acquire the sound joints.When bonded at low temperture, binary or trinary inmermetallics composed of Al,Si,Ti apperaed in the interface, and Al-12Si eutectic structure apperaed in the center of the interface with Al-12Si filler metal. With increasing the joinning temperture, intermetallic became more and thick. The shear strength of this joint was lower because of thin aluminium layer between the intermetallic layer and eutectic structure.The interface structure of the joint was pure alunimiun and TiAl3 intermetallic when brazed in 45 min at 700℃with aluminium filler metal. The thickness of intermetallic grew and the shear strength descended with increasing the holding time. Transversal crack and shrinkage cavity appeared in the joint when the holding time was more than 90 min, which caused the joint mechanical property deteriorated.The commercial titanium based brazing alloy was used to joint the substrate. Holding the joining time 10 min, two conversion zones were found when the joining temperture was low. Fusional filler metal diffused into the base metal and the substrates dissovlved into the fusional brazing metal. The joint was consituted ofα+βdual structure at 950℃. When hydrogen content was less than 0.3wt%, the shear strength first increased, than had a maxmium value at 950℃, and at last decreased slowly. When hydrogen content is more than 0.3wt%, the shear strength increased slowly all the time and only got 324MPa at 980℃.