Relationship between microstructure and mechanical properties of a 5% Cr tempered martensitic tool steel

Relevant microstructural characteristics ensuring a good mechanical strengthening up to 600 °C of a tempered martensitic steel containing 5% Cr (AISI H11) were investigated using transmission electron microscopy, energy-dispersive X-ray analysis, X-ray diffraction and extraction of carbides. Softening induced by tempering and cyclic loading is related to a strong reduction of the dislocation density estimated by X-ray peak profile analysis (modified Williamson Hall and modified Warren Averbach analysis). Moreover, the coalescence of chromium and vanadium carbides is involved in the yield strength decrease above 600 °C and during cyclic loading.