Microstructure evolution and mechanical properties of eutectoid steel with ultrafine or fine (ferrite+cementite) structure

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• 作者：Chengsi Zheng^a ; Longfei Li^a ; ^{lilf@skl.ustb.edu.cn" class="auth_mail} ; Wangyue Yang^b ; Zuqing Sun^a
• 关键词：Eutectoid steel ; Hot deformation of undercooled austenite ; Cementite particles ; Mechanical properties ; Work-hardening capability
• 刊名：Materials Science and Engineering: A
• 出版年：2 April, 2014
• 年：2014
• 卷：599
• 期：Complete
• 页码：16-24
• 全文大小：3161 K

文摘

Eutectoid steel with the ultrafine or fine-grained ferrite (伪)+cementite (胃) particles structure was formed by hot deformation of undercooled austenite at 0.1 s^鈭? or 5 s^鈭? at 650 掳C using a Gleeble 1500 hot simulator and subsequent annealing. The microstructural evolution of fine (伪+胃) structure was investigated by means of a scanning electronic microscope, electron backscattered diffraction and transmission electron microscope, and the mechanical properties of fine (伪+胃) steel were analyzed in comparison with that of ultrafine (伪+胃) steel. The results show that only dynamic transformation of undercooled austenite into proeutectoid ferrite occurs during hot deformation at 650 掳C at 5 s^鈭?. During water quenching, lamellar pearlite with small colony sizes is formed and the average size of pearlite colonies decreases with increasing the strain. By subsequent annealing at 650 掳C for 30 min, the spheroidization of lamellar pearlite takes place, resulting in the formation of fine (伪+胃) structure consisting of ferrite matrix with the average size of about 4.9 渭m and fine cementite particles mainly within ferrite grains. In comparison with ultrafine (伪+胃) steel consisting of ferrite matrix with the average size of about 1.8 渭m and relatively large cementite particles mostly located at grain boundaries, the yield strength, tensile strength, uniform elongation, total elongation and work-hardening capability of fine (伪+胃) steel improve markedly.