New phase transition pattern of fivefold twins transformed into lamellar structure in Ti3Al alloy

The structures of fivefold twin (FFT) and lamellar (LAM) are the primary configurations during the crystallization of alloys. However, the co-existence of two structures in one system and conversion mechanism...

The Influence of Ti-6-4 Alloy Interlayer on Ti3Al Alloy DB Quality and Interface Mechanical Properties

Ti3Al intermetallic alloy is a light and high-temperature resistant material which substitutes for superalloy. It is promising for wide use in aerospace yield. In this paper, the Ti3Al alloy was joined by diffusion bonding with and without Ti-6-4 alloy interlayer respectively. Diffusion bonding quality and shear strength of the joints were measured and compared. The results show that there was almost no defect found in joints with interlayer and maximum shear strength is 523 MPa in conditions of 940°C and 2.5 MPa pressure for 1.5h. In contrast, defect rate (percentages of sum of defects length in optical micrograph) of joints without interlayer exceeds 80% and maximum shear strength is only 150 MPa in same conditions. According to fracture analysis, the ductile fracture occurred at Ti-6-4 interlayer of joint with interlayer. Fracture of joint without interlayer belongs to mixed type of ductile fracture and brittle fracture.