Anomalous martensite transformation mechanism induced by additive manufacturing

Abstract

Maraging steel is extensively used as an indispensable material in various fields such as defense and aerospace thanks to its ultrahigh strength deriving from the combination of martensitic matrix with a high density of dislocation and intermetallic precipitates formed during aging treatment. However, conventional processing of maraging steel involves complex and time-consuming processing steps, accompanying multiple melting, hot/cold working, machining, welding, and heat treatment. Recently, additive manufacturing (AM) has emerged as a next-generation metal processing technology for maraging steel due to its availability of rapid fabrication for complex-shaped metal components. Even though maraging steel fabricated by AM has been studied consistently, the cause and mechanism of different microstructures have not been unveiled so far. Therefore, in this thesis, the effect of AM on the microstructural evolution of maraging steel was clarified and the corresponding martensite transformation mechanism was proposed.