Microstructure and mechanical properties of JLF-1 and CLAM steels exposed to thermal aging with stress

In this work, effects of low levels of stress during aging at 823 and 973 K for 100 h on mechanical properties and microstructures were investigated for JLF-1 and CLAM steels. The results showed that hardness decreased and tensile strength increased after aging at 823 K for 100 h with stresses from 9 to 100 MPa for the both steels. The improvement of tensile properties was due to increase in number density of precipitates, especially with small size. On the contrary, hardness, tensile and creep strength decreased after aging at 973 K for 100 h, suggesting softening. The degradation of these properties was accelerated by applying stresses of 30 and 50 MPa during the aging. Decrease in number density of precipitates, partial recovery of martensitic structures and coarsening of lath width, were responsible for the degradation of mechanical properties at 973 K for 100 h and under applied stress. (author)