1. School of Materials Science and Engineering，Kunming University of Science and Technology，Kunming 650093， Yunnan，China 2. Institute for Special Steels， Central Iron and Steel Research Institute，Beijing 100081，China
Abstract：The effect of preheat treatment on microstructure and mechanical properties of AMS 6308 steel was investigated experimentally by means of SEM， TEM and mechanical properties tests. The results show that with elevating the normalizing?temperature， M6C carbides dissolve gradually and grain size is small when normalized below 980 ℃， the martensite lath size is small， spherical and axiolitic M6C carbides precipitate along lath boundaries and grain boundaries， the content of M6C carbides and the dislocation density is very high after quenching， which leads to an increase of strength and toughness. While the steel sample is normalized above 980 ℃， the strength and toughness decrease duo to the increase of the martensite packet size and the decrease of the content of M6C carbides and the dislocation density. The recommended preheat treatment process includes： normalizing at 980-1 010 ℃， and tempering at 680-700 ℃， AMS 6308 steel shows a good combination of strength and toughness after property heat treatment.
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2016, Vol. 51 
