Investigation of nanoscale dual-precipitation behavior in 4Cr16MoCu martensitic stainless steel under varied tempering temperatures

Abstract

Nanoscale dual-precipitation in 4Cr16MoCu martensite stainless steel was investigated after tempering at 400 °C, 500 °C and 600 °C. Atom probe tomography (APT) was utilized to quantify the growth pattern of Cu-rich phase and eutectoid behavior of the co-located Cu-rich phase and M23C6 carbide precipitates. With the increase in tempering temperature, the size of Cu-rich phase continued to grow while their number decreased. Meanwhile, significant changes of the aggregation positions of Ni and Mn in Cu-rich particles were observed, shifting from the center of Cu particles when tempering at 500 °C to their periphery at 600 °C. During the precipitation process, closely adjacent Cu-rich particles were confirmed surrounding the carbides, indicating that carbides contribute to the nucleation of Cu-rich phase. Furthermore, despite their proximity, no mutual compositional encroachment between the precipitates was detected. In addition, the dislocation proliferation induced by the solid phase transition of Cu particles has also been confirmed.