부산대학교 도서관

To solve the problem that cracks and brittle Ti-Al intermetallic compounds restrict the mechanical properties of Ti-Al joint, an effective connection method has been explored for laser welding of TC4 titanium alloy and 7075 aluminum alloy by oscillating laser beam, and the effect of oscillating laser beam on the interface and mechanical properties of Ti/Al fusion welding joint was also investigated. With the application of beam oscillation, some defects like pores and cracks can be avoided in welding joint, the connection width of interface layer is increased, and the diffusion of Al-to-Ti is suppressed due to the reduced interfacial heat input and the stirring effect induced by the keyhole rotating. As a result, Al-rich Ti-Al compound at interface is reduced while Ti-rich compound is formed. Generally, the property of Ti/Al joint can be significantly improved by the reduction of joint defects and the formation of lower brittle TiAl/Ti3Al compounds. As the oscillation frequency increase, the maximum load of the joint increases first but then decreases, and reached the highest value of 1852N when the 150 Hz oscillating frequency is applied, representing 76.38% enhancement compared with that without oscillation. However, under the condition of excessive oscillating frequency, the interface layer is too thin to form an effective connection, which deteriorates the joint properties.