焊缝金属解理断裂微观机理

发布时间：2018-05-19 06:05

本文选题：解理断裂 + 断裂过程　；参考：《金属学报》2017年11期

【摘要】：本文为低合金高强钢的解理断裂提出了一个新的理论框架:解理断裂不仅决定下平台的冲击韧性,而且对过渡温度区的韧性也起决定性的作用,因为在这个温度区间韧性取决于先前产生的塑性裂纹扩展的长度,而解理断裂终止了塑性裂纹的扩展,从而决定其长度。解理断裂包含3个不间断的阶段:(1)裂纹在第二相颗粒起裂成核;(2)第二相裂纹穿过第二相颗粒和晶粒边界扩展;(3)晶粒裂纹穿过晶粒边界扩展进入相邻晶粒。本理论框架对整个过程进行了诠释:解理断裂的临界事件是在裂纹形成过程中提供最大困难的阶段,它控制了解理断裂过程,并确认了最薄弱的微观组分及其临界尺寸,这个尺寸决定了微观解理断裂应力sf。在断裂过程研究中最为重要的就是揭示各种条件下断裂的临界事件。提出引发解理断裂的3个准则:(1)裂纹起裂成核准则;(2)防止裂纹核钝化准则;(3)裂纹扩展准则。并由这3个准则形成了一个活性区,在活性区中应力和应变的综合作用可以引发解理断裂,这个活性区被用来建立断裂的统计模型。本研究利用这个新的理论框架进行了8%Ni钢焊缝的实例研究,以说明实验研究的结果。
[Abstract]:This paper presents a new theoretical framework for the cleavage fracture of low alloy high strength steel. Cleavage fracture not only determines the impact toughness of the lower platform, but also plays a decisive role in the toughness of transition temperature region. Because the toughness at this temperature range depends on the length of the previously produced plastic crack propagation, the cleavage fracture terminates the plastic crack growth, thus determining its length. The cleavage fracture consists of three uninterrupted stages: 1) crack nucleation in the second phase particle initiation and nucleation (2) the second phase crack propagates through the second phase particle and the grain boundary propagation / 3) the grain crack propagates through the grain boundary to the adjacent grain. This theoretical framework interprets the whole process: the critical event of cleavage fracture is the most difficult stage in the process of crack formation, which controls the understanding of the process of microfracture, and confirms the weakest microscopic component and its critical size. This size determines the microcleavage fracture stress sf. The most important thing in the study of fracture process is to reveal the critical events of fracture under various conditions. Three criteria for initiation of cleavage fracture are proposed: 1) crack initiation and nucleation criterion and 2) prevention of crack nucleation and passivation criterion and 3) crack growth criterion. From these three criteria, an active zone is formed, in which the combined action of stress and strain can induce cleavage fracture, and this active zone is used to establish the statistical model of fracture. In order to illustrate the experimental results, a case study of weld seam of 8%Ni steel has been carried out by using this new theoretical framework.
【作者单位】：兰州理工大学省部共建有色金属先进加工与再利用国家重点实验室;兰州理工大学材料科学与工程学院;
【基金】：国家自然科学基金项目Nos.51675255和51761027~~
【分类号】：TG142.1

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