Solid phase transition of Cu precipitates in a low carbon TRIP assisted steel

Abstract

Abstract The evolution behavior of Cu precipitates under intercritical tempering in a low carbon low alloy steel is presented in the study here. A complete crystal structure transformation process of Cu precipitate is presented together with newly discovered steps. The complete transformation sequence of crystal structure of Cu precipitates in the alloy system was (I) Cu-rich nano-order clusters→9R Cu→detwinned 9R Cu→transition phase (detwinned 9R\xa0+\xa0FCC)→FCC Cu and (II) Cu-rich nano-order cluster→non twin 9R Cu→FCC Cu. The entire evolution process of Cu precipitates was caused by the continuous enrichment of Cu atoms in Cu precipitates and the size of Cu precipitates. In the present study, we have discovered the increase of Cu content in Cu-rich nano-ordered clusters, the movement rule of twin planes and the combination of twin variants in the multiple twin 9R Cu, the transition rule from 9R structure to FCC structure.