Intermetallic regulation mechanism of inconel 718/Ti6Al4V composite by novel follow-up ultrasonic assisted laser additive manufacturing

Brittle intermetallic phase is easily formed in titanium alloy/superalloy composite, and this phase can increase the risk of cracking and limit the performance and application of titanium alloy/superalloy gradient materials. In this investigation, 20 wt% Inconel 718 + 80 wt% Ti6Al4V composite is prepared by a novel method of follow-up ultrasonic assisted laser additive manufacturing . Follow-up ultrasonic can keep the relative position of the molten pool and the ultrasonic tool head to guarantee the continuous intensity of the ultrasonic in the molten pool. The high-intensity impact generated by the cavitation effect of the ultrasonic refines and break the chain intermetallic phase (Ti 2 Ni), and increases the content of granular intermetallic phase. In addition, the acoustic streaming effect of ultrasonic promotes the uniform distribution of elements and inhibits the segregation of Ni element. Meanwhile, the ultrasonic vibration promotes the thermal convection of samples and increases the cooling rate to shorten the transition time from β-Ti to Ti 2 Ni. This is beneficial to suppress the generation of Ti 2 Ni. The content of intermetallic phase in the composite is 11.6% without ultrasound, and decreases by 48.3% to 6.0% with the application of 1200 W ultrasonic power, and the distribution uniformity increases by 37.5%. The proportion of intergranular brittle fracture in the mixed fracture of the composite is decreased, and the bending strength increases from 805 MPa without ultrasound to 1047 MPa with 1200 W ultrasonic power, which increased by 30.1%. Through the intervention of the follow-up ultrasonic, the microstructure and properties of the composite are effectively controlled.