Consequences of rapid heating of Al–Cu alloy and martensitic stainless steel

In its first part, the paper describes the mechanism of constitutional liquation and specifies the conditions favourable to this phenomenon. Then, two case studies of service failure caused by non-equilibrium liquation in AlCu4MgSi alloy and in stainless steel X46Cr13 are analysed. Components made of these alloys were subject to solution annealing during their manufacturing process. Too fast heating resulted in non-equilibrium liquation between precipitates and matrix of these alloys in subsolidus temperatures. In consequence, irreversible changes occurred in microstructure, which directly contributed to service failures of the components, i.e. intergranular corrosion of the aluminium alloy and seizure of the steel shaft in its slide bearing.

► Rapid heating rate and large precipitate size promote constitutional liquation (CL).
► Two parts made of AlCu4MgSi alloy and X46Cr13 steel were solution annealed.
► Changes in microstructure due to CL caused their failure during service.
► Susceptibility of alloys to CL depends on size and distribution of second phase.
► Microstructure of semi-product should be controlled before heating.