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金属学报  2015, Vol. 51 Issue (9): 1136-1144    DOI: 10.11900/0412.1961.2015.00091
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考虑位错相互作用的混合控制模型下先共析铁素体生长动力学模拟
武慧东,张弛,柳文波,杨志刚()
SIMULATION OF GROWTH KINETICS OF PRO-EUTECTOID FERRITE USING MIXED CONTROL MODEL WITH CONSIDERATION OF DISLOCATION INTERACTION
Huidong WU,Chi ZHANG,Wenbo LIU,Zhigang YANG()
Key Laboratory of Advanced Materials of Ministry of Education, School of Materials Science and Engineering, Tsinghua University, Beijing 100084
引用本文:

武慧东,张弛,柳文波,杨志刚. 考虑位错相互作用的混合控制模型下先共析铁素体生长动力学模拟[J]. 金属学报, 2015, 51(9): 1136-1144.
Huidong WU, Chi ZHANG, Wenbo LIU, Zhigang YANG. SIMULATION OF GROWTH KINETICS OF PRO-EUTECTOID FERRITE USING MIXED CONTROL MODEL WITH CONSIDERATION OF DISLOCATION INTERACTION[J]. Acta Metall Sin, 2015, 51(9): 1136-1144.

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摘要: 

建立了考虑伴随台阶的位错间相互作用的界面反应-扩散混合控制模型, 并利用该模型对先共析铁素体2个台阶以及多个台阶的生长过程进行模拟. 结果表明, 当只有2个台阶且其水平距离大于临界距离时, 台阶之间相互吸引, 能在一定程度降低领先台阶的生长速率; 当2个台阶水平距离小于临界距离时, 台阶之间相互排斥, 增大领先台阶的生长速率; 多台阶的情形下, 伴随台阶的位错之间相互作用, 台阶的合并规律发生改变, 并对台阶生长速率产生一定影响.

关键词 先共析铁素体混合控制模型台阶生长动力学    
Abstract

During austenite to ferrite transformation, the lattice structure transforms from fcc to bcc, resulting in a clearly distinguishable austenite and ferrite interface. The short range diffusion of the Fe and C atoms across the interface causes its movement, referred to as interface migration. On the other hand, the C rejected by the ferrite during the austenite to ferrite transformation in Fe-C alloys accumulates ahead of the moving interface. This pile-up of C atom is dependent on the long range diffusion of C in austenite and also influences the ferrite growth kinetics. Experimental observations indicate that dislocations are always migrating with ledges during ledgewise growth. The local stress field of dislocations is considered to alter the solute concentration at the riser of ledges and causes a complex diffusion field interaction among ledges as they migrate. Some established works by other researchers have already taken the effect into consideration when studying phase transformation kinetics. However, these works were limited in diffusion control cases and could hardly explain some experimental results. In this work, a ledgewise growth model considering migration of austenite/ferrite interface, C diffusion in austenite and especially elastic interactions between dislocations moving with ferrite ledges was established, and all the simulated results were qualitatively similar to the reported experimental results. Calculated results showed that the C concentration at the riser of ledges was changed by the elastic stress of these dislocations, which would further change the growth behavior of ledges. In the growth behavior simulations of two ledges, the horizontal distance of the two ledges was found to be a key role to determine the growth kinetics. When the horizontal distance of two ledges was larger than the critical distance, an attractive phenomenon of the two ledges was found to decelerate the leading step; while a repulsive phenomenon of the two ledges which would accelerate the leading ledge if the horizontal distance was smaller than this value. Compared with the simulation results without considering elastic interactions between dislocations, however, in the growth behavior simulations of multi-ledge with elastic dislocation interactions, the coalescence behavior of ledges and growth rate of the leading step were both changed.

Key wordspro-eutectoid ferrite    mixed-control model    ledgewise growth kinetics
    
基金资助:*国家自然科学基金项目 51171087 和 51471094 资助
图1  每个台阶含1个位错的示意图
图2  奥氏体-铁素体界面扩散通量示意图
图3  计算得到cm2 和cm’2的图解
图4  作用于单位长度台阶上的力Fx 及Fx 引起的台阶1 前沿C浓度变化Δcm 与2 台阶水平距离Xd 的关系
图5  Fe-0.34%C合金在720 ℃等温γ →α 转变时间为T1时考虑和不考虑台阶位错相互作用情况下2 台阶铁素体形貌模拟结果
图6  总相变时间为T1, Fe-0.34%C合金在720 ℃等温γ →α转变时2台阶分别在考虑和不考虑台阶位错相互作用情况下U和V随T的变化
图7  Fe-0.34%C合金在720 ℃等温γ →α 转变时间为T2时考虑和不考虑台阶位错相互作用情况下2 台阶铁素体形貌模拟结果
图8  总相变时间为T2, Fe-0.34%C合金在720 ℃等温γ →α 转变时2 阶分别在考虑和不考虑台阶位错相互作用情况下U和V随T的变化
图9  Fe-0.34%C合金在720 ℃等温γ →α 转变时间为T2时考虑和不考虑台阶位错相互作用情况下10 台阶铁素体形貌模拟结果
图10  Fe-0.305%C合金在740 ℃等温γ →α 转变时台阶1 的生长速率v1和长度L1随时间t变化
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