铁素体球墨铸铁低温冲击断裂裂纹形核及扩展机理

发布时间：2018-02-11 09:58

本文关键词： 石墨球韧脆转变解理断裂形变孪晶　出处：《金属学报》2015年11期 　论文类型：期刊论文

【摘要】：在低温下对QT400-18L铁素体球墨铸铁件进行Charpy缺口示波冲击实验,测试温度对冲击过程中裂纹形核和裂纹扩展能力的影响,采用OM观察分析不同温度下铁素体球墨铸铁裂纹萌生与扩展路径以及断口附近组织的演变规律.结果表明,韧脆转变温度以上,冲击后断口附近大量石墨-基体界面发生开裂,石墨界面开裂后产生的孔洞起到钝化裂纹和降低裂纹扩展速率的作用;韧脆转变温度区间,冲击试样表现为韧窝和解理混合断口形貌,断裂模式和裂纹形核均与石墨球有关;韧脆转变温度以下,垂直交叉孪晶成核进而导致微裂纹扩展,解理断裂主要是孪晶起裂,这种形变孪晶引起的裂纹形核和扩展方式造成了裂纹形成功与裂纹扩展功的剧烈下降.
[Abstract]:The Charpy notched oscillographic impact test was carried out on QT400-18L ferrite ductile iron at low temperature. The effect of temperature on crack nucleation and crack propagation was tested. OM was used to observe and analyze the crack initiation and propagation path of ferrite ductile iron at different temperatures and the evolution law of the microstructure near the fracture surface. The results showed that a large number of graphite-matrix interface cracks occurred near the fracture surface after impact when the ductile and brittle transition temperature was higher than the transition temperature. The pore produced by graphite interface cracking plays a role of passivation of crack and decreasing of crack propagation rate. In the range of ductile-brittle transition temperature, the fracture pattern and crack nucleation are all related to graphite spheroids, and the impact specimens exhibit mixed fracture morphology of dimple and debonding mechanism, and the fracture mode and crack nucleation are related to graphite spheroids. Below the ductile and brittle transition temperature, the vertical cross twin nucleation leads to microcrack propagation, and cleavage fracture is mainly twin initiation. The crack nucleation and propagation caused by deformation twin cause the crack shape success and crack propagation work decrease sharply.
【作者单位】：沈阳工业大学材料科学与工程学院;
【基金】：国家自然科学基金项目51274142 辽宁省自然科学基金项目2014028015 沈阳市科技局项目F15-199-1-15资助~~
【分类号】：TG143.5

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