Effect of thermomechanical treatment on MX phase precipitation behavior in CLAM steel

Reduced Activation Ferritic/Martensitic (RAFM) steels are the preferred first wall structural materials in nuclear fusion experimental reactors at this stage, which puts forward high requirements for its creep properties. Previous references point out that the main factor for the creep resistance of RAFM steel is the massively precipitated MX phases in the matrix. Thermomechanical treatment (TMT) technology can promote the precipitation of a large number of nano-sized MX phases, and has great potential for improving the creep strength of RAFM steels. In this paper, China Low Activation Martensitic (CLAM) steel is taken as the research object, and four different thermomechanical treatment processes are designed for comparison. The purpose is to deepen our understanding of the effects of austenitization temperature, deformation temperature and strain on the precipitation of MX phases. It is found that the number density of MX phase after TMT increases by two orders of magnitude, and the average particle size decreases by about 79% when the austenitization temperature increases from 1000 to 1150 °C, while the effect of deformation temperature and strain is relatively small; after TMT, the specimen with the largest number and the smallest size of MX phase has the best creep performance, and vice versa.