Multiple process microstructure evolution simulation of ultrasonic assisted rolling directed energy deposition

Abstract

Directed energy deposition (DED) has a widely application prospect, but dendrite and component segregation are not easily controlled and predicted. In this study, the method of applying ultrasonic assisted rolling was introduced to the DED to eliminate above phenomenon. A multiple process microstructure evolution simulation (involved melting, solidification, dynamitic recrystallization and grain growth) was also carried out, which introduced ultrasonic effect in the form of energy. The influence of ultrasonic amplitude (A), distance between laser focus point and ultrasonic roller (d0) on microstructure of Pb-Sn alloy deposition layer were explored. There is a good consistency between experiment and simulation with relative error of 4.33%. The results show that the roundness of grains is improved significantly after rolling, and the grain are refined with the increase of A and d0. In all tests of this study, comprehensive effect of ultrasonic rolling achieves the best when d0 is taken as 24 mm and A is taken as 20 μm, the average grain diameter (D0) in grain size counted zone is 18.8 μm which is 23.23% lower than that without rolling. This study laid a foundation for the development of ultrasonic assisted rolling DED and provide a multiple process microstructure simulation method.