Abstract: Formation reason of radial stripes in эи866 alloy forgings were analyzed by microstructure observation, mechanical properties and hardness testing. The heat treatment process to eliminate the radial stripes was also studied. The results show that the radial stripes are caused by the banded structure. A large amount of retained austenite remains after quenching, and transforms to secondary martensite in the tempering cooling process. The secondary martensite distributes alternately with the tempered martensite to form the banded structure, which results in the hardness nonuniformity and appears stripes after machining. Adding a secondary tempering after the performance heat treatment can make the martensite to decompose and recover, and the banded structure can be improved, but it is difficult to be completely eliminated. Adding preheat treatment before the performance heat treatment can raise the Ms point, make the martensite transformation sufficiently, and reduce the amount of retained austenite greatly after quenching, then a single uniform tempered martensite is formed, and the banded structure is eliminated completely. Thus, it is suggested to couple the preheat treatment with the performance heat treatment to improve the uniformity of the structure in the эи866 alloy forgings.

Key words: эи866 alloy, banded structure, retained austenite, preheat treatment