Mechanism of Stress Relief Cracking in a Granular Bainitic Steel

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• 作者：Zai-Song Yu ; Jian-Xun Zhang ; Hong-Zhe Wang…
• 关键词：Granular bainitic steel ; Heat ; affected zone ; Stress relief cracking ; Martensite/austenite island ; Behavior of grain boundary
• 刊名：Acta Metallurgica Sinica (English Letters)
• 出版年：2017
• 出版时间：February 2017
• 年：2017
• 卷：30
• 期：2
• 页码：156-163
• 全文大小：
• 刊物主题：Metallic Materials; Spectroscopy/Spectrometry; Organometallic Chemistry; Tribology, Corrosion and Coatings; Nanotechnology; Characterization and Evaluation of Materials;
• 出版者：The Chinese Society for Metals
• ISSN：2194-1289
• 卷排序：30

文摘

Coarse-grained heat-affected zone (CGHAZ) of a low alloyed, granular bainitic steel T24 was simulated in a Gleeble apparatus. The stress relief of the CGHAZ was analyzed by annealing the samples. The morphology and behavior of the microstructure near the grain boundaries during stress relief were investigated by means of focused ion beam, in situ tensile testing, transmission electron microscopy, scanning electron microscopy and electron back-scatter diffraction. It was observed that there were large martensite/austenite islands distributed along the grain boundaries of CGHAZ. During stress relief at elevated temperature, the retained austenite at the grain boundaries decomposed into M₃C carbides and a ferrite forming softening zone. Together with the stress relief, piled up of dislocations occurred within the ferrite in the area adjacent to the ferrite/M₃C interface, which resulted in high level of stress accumulation and caused crack initiation along the grain boundaries. These results indicate that the stress relief induced the grain boundary crack is controlled by other mechanisms rather than the creep-like grain boundary sliding.