Stress-strain Behavior of Ferrite and Bainite with Nano-precipitation in Low Carbon Steels
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摘要: 系统研究了存在纳米尺寸碳化钒析出的铁素体和贝氏体相低碳钢的应力-应变行为。通过奥氏体/铁素体转变并结合相间析出制取组织为铁素体相的试样,通过奥氏体/贝氏体转变,随后进行时效制取贝氏体相试样。两种试样的应力-应变曲线具有几个共同特征:高屈服应力、相对低的加工硬化特性以及足够高的伸长率。根据组织参数计算了溶质原子、晶界、位错和析出物对强度的贡献,并将计算结果与试验测定的应力结果进行对比。溶质原子和晶界强化贡献可以简单地相加,而位错和析出物对强度的贡献大小应表示为两者平方和的平方根。纳米尺寸碳化物在拉伸变形早期阶段可能充当位错增生源的作用,而在变形后期则加速位错湮灭。这种增加型动态回复可能造成铁素体相和贝氏体相这两种钢都具有相当高的伸长率。Abstract: We systematically investigate stress-strain behavior of ferrite and bainite with nano-sized vanadium carbides in low carbon steels; the ferrite samples were obtained through austenite/ferrite transformation accompanied with interphase precipitation and the bainite samples were via austenite/bainite transformation with subsequent aging.The stress-strain curves of both samples share several common features,i.e.high yield stress,relatively low work hardening and sufficient tensile elongation.Strengthening contributions from solute atoms,grain boundaries,dislocations and precipitates are calculated based on the structural parameters,and the calculation result is compared with the experimentally-obtained yield stress.The contributions from solute atoms and grain boundaries are simply additive,whereas those from dislocations and precipitates should be treated by taking the square root of the sum of the squares of two values.Nanosized carbides may act as sites for dislocation multiplication in the early stage of deformation,while they may enhance dislocation annihilation in the later stage of deformation.Such enhanced dynamic recovery might be the reason for a relatively large elongation in both ferrite and bainite samples.
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Key words:
- low carbon steel /
- vanadium carbide /
- nano-precipitation /
- interphase precipitation /
- aging /
- mechanical property
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