Abstract
The precipitate hardened plastic mould steel 10Ni3MnCuAl after aging at 510°C is investigated by optical microscopy, X-ray diffractometry, TEM and three-dimensional atom probe. The results show that its microstructure is granular bainite with a certain amount of retained austenite after soluted and cooled in furnace, and its content decreases until close to 0. By TEM observation, the age hardening of the 10Ni3MnCuAl steel is mainly ascribed to the precipitation of a high density, ultrafine and fully coherent NiAl precipitation with the B2 structure at 510°C for 4 h, and a multicomponent precipitate can be found in steel for 100 h aging. The three-dimensional atom probe researches show that its age hardening derives from a spherical multicomponent precipitate containing Fe, Ni, Al, Mn and Cu, and the content of Fe decreases with aging time, while those of Ni, Al, Mn and Cu are opposite, and the ratio between Ni and Al is roughly 1, and the Cu precipitates are surrounded by Ni, Al and Mn clusters for 100 h aging. The hardness variation is related to the size and number density of the precipitates, and it follows the cutting mechanism during early aging while obeys Orowan mechanism during overaging.
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