一种新型980MPa高强钢的弯曲断裂机理  

Bending Fracture Mechanisms of a 980MPa High Strength Steel

作　　者：曹睿[1] 闫英杰[1] 杜挽生[2] 彭云[2] 田志凌[2] 陈剑虹[1] 

机构地区：[1]兰州理工大学甘肃省有色金属新材料省部共建国家重点实验室,甘肃兰州730050 [2]钢铁研究总院结构材料研究所,北京100081

出　　处：《材料科学与工程学报》2009年第5期696-700,共5页Journal of Materials Science and Engineering

基　　金：科技部"863"计划子课题资助项目(2006AA03A206);国家自然科学基金资助项目(50671047);高等学校博士点基金资助项目(20060731001)

摘　　要：本文结合不同试验温度下一种新型980MPa高强钢预裂纹COD试验的宏观试验结果以及详细的微观断裂表面观察,研究了这种高强钢的断裂行为。研究结果表明:高强钢具有相当优越的断裂韧性,转变温度大约为-150℃。在-196℃的温度下,准解理开裂控制了整个断裂过程,但它仍然不能扩展通过整个韧带,在宏观曲线上出现POP-IN的扩展特征,微观上表现为准解理特征和韧性撕裂特征断口交替出现;同时发现阻止裂纹扩展的阻力来源于三个方面:原奥氏体晶粒边界,贝氏体团边界以及贝氏体片。这些障碍物在断面上以韧窝形式的撕裂脊出现。在高温下,断裂机理主要是以纤维开裂为主,断口形态主要表现为韧窝断裂面,并有少量单独准解理面。Combining experimental results of COD tests at different temperatures with microscopic observations of fracture surfaces and crack configurations on the unloaded specimens,fracture behavior of a 980MPa high strength steel was investigated. The results revealed that this high strength steel possessed superior toughness with a transit temperature around-150℃.Even though the cleavage cracking dominates the fracture process at a very low temperature（-196℃）,but it cannot propagate straightly forward through entire ligament,showing the pop-in extension in macroscopic tests and the quasi-cleavage mode in microscopic feature.It is found that the strong resistance to crack propagation is provided by three barriers： original austenite grain boundaries,bainite colony boundaries and inter-layers between bainite laths.These barriers manifest themselves by tear ridges with dimples on the fracture surfaces.At higher temperatures,the fracture mechanism is dominated by fibrous cracking which makes dimpled fracture surface with some individual quasi-cleavage facets.

关 键 词：980MPa高强钢 断裂机理 POP-IN 温度影响 

分 类 号：TG301[金属学及工艺—金属压力加工]