TY - JOUR ID - 4781 TI - Limit of Dislocation Density and Ultra-Grain-Refining on Severe Deformation in Iron JO - International Journal of Iron & Steel Society of Iran JA - IJISSI LA - en SN - 2981-0388 AU - Takaki, Setsuo AD - Dept. of Materials Science and Engineering, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan, Y1 - 2005 PY - 2005 VL - 2 IS - 1 SP - 21 EP - 25 KW - Iron KW - Grain refinement KW - Uni-directional deformation KW - Multi-directional deformation KW - Stored strain KW - Dislocation density KW - Grain size KW - Dynamic continuous recrystallization DO - N2 - It is well-known that severe deformation to metals causes a direct grain refinement of the matrix without special heat-treatments due to the mechanism of dynamic continuous recrystallization (DCR). However, the microstructural revolution during severe deformation is seemed to be different depending on the deformation mode, namely the direction of deformation. In general, multi-directional deformation is thought to be effective for the grain refinement caused through DCR. For instance, ultra-grain-refinement to 10nm has already achieved by mechanical milling treatment in a steel powder and hardness of mechanically milled steel powder is increased to around HV12GPa by such a marked grain refinement. On the other hand, hardness of iron never exceeds HV4GPa by the mode of uni-directional deformation such a conventional cold rolling. In this paper, a limit of dislocation density is discussed for iron which is severely strained by the mode of uni-directional deformation, and also the importance of multi-directional deformation on DCR will be mentioned in association with a significant work hardening behavior in mechanically milled iron powder UR - https://journal.issiran.com/article_4781.html L1 - https://journal.issiran.com/article_4781_8e338de669e8f44d09d6dc7c67de265c.pdf ER -