中碳钢过冷奥氏体形变过程中的组织演变  

MICROSTRUCTURE EVOLUTION OF MEDIUM CARBON STEEL DURING DEFORMATION OF UNDERCOOLED AUSTENITE

作　　者：陈国安[1] 杨王玥[1] 孙祖庆[2] 

机构地区：[1]北京科技大学材料科学与工程学院,北京100083 [2]北京科技大学新金属材料国家重点实验室,北京100083

出　　处：《金属学报》2007年第1期27-34,共8页Acta Metallurgica Sinica

基　　金：国家自然科学基金项目50471092;教育部博士点基金项目20050008017资助

摘　　要：利用热模拟压缩变形实验研究了不同形变温度以及形变速率下中碳钢过冷奥氏体形变过程中的组织演变规律,探讨了中碳钢珠光体球化以及组织超细化的机理．结果表明:组织演变主要经历了动态铁素体相变、动态珠光体相变以及珠光体的球化3个阶段．为获得亚微米级别铁素体和颗粒状渗碳体弥散分布的复相组织,需要形变温度与形变速率的配合．形变过程中珠光体球化速率比等温球化退火快4个数量级,其原因是在形变过程中产生了高密度位错及大量空位等缺陷,为碳原子的扩散提供了高速率扩散通道,促进了碳原子的扩散．渗碳体粒子在铁索体基体上的弥散分布可用溶解－再析出机制解释．The microstructure evolution of a medium carbon steel （0.48℃） during deformation of undercooled austenite at different temperatures and strain rates has been investigated by means of uniaxial hot compression simulation experiment. The predominant mechanism on the formation of ultrafine （α ＋ θ） microduplex structures has been explored. The experimental results showed that the process of microstructure evolution can be divided into three stages： dynamic ferrite transformation, dynamic pearlite transformation and spheroidization of lamellar pearlite. An optimum combination of deformation temperature and strain rate is required to obtain ultrafine （α ＋ θ） microduplex structures. A large number of vacancies and high density dislocations introduced during hot deformation provided short-circuiting paths for diffusion of carbon atoms, therefore the rate of cementite spheroidization was accelerated by four orders of magnitude as compared to a static annealing treatment. The observed redistribution of cementite particles in the ferrite matrix can be interpreted in terms of dissolutionreprecipitation mechanism.

关 键 词：中碳钢 动态相变 珠光体球化 晶粒细化 碳的扩散 

分 类 号：TG111.2[金属学及工艺—物理冶金] TG142.31[金属学及工艺—金属学]