The 17-4PH alloy is a martensitic stainless steel with 3–5 wt% Cu, strengthened by the precipitation hardening. Due to excellent mechanical properties, corrosion resistance and ease of heat treatment, this alloy has unique applications in nuclear power plants and marine constructions. In this paper, the influence of ageing heat treatment, solution annealing followed by ageing at 480, 550 and 62...