Fracture behaviour of 8%Ni 980 MPa high strength steel at various temperatures Part 2 – COD tests
Fracture behaviour of 8%Ni 980 MPa high strength steel at various temperatures Part 2 – COD tests
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DOI：
10.1179/174328409x439169
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发表时间：
2011-01
影响因子：
1.8
通讯作者：
R. Cao;Y. Yan;W. Du;Z. Tian;Y. Peng;J. H. Chen
中科院分区：
文献类型：
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作者：
R. Cao;Y. Yan;W. Du;Z. Tian;Y. Peng;J. H. Chen
结合不同温度下的裂纹张开位移(COD)试验结果，结合断口和断口形貌的详细观察，研究了8Ni980 Mpa级高强度钢的断裂行为。结果表明，该高强度钢具有较高的韧性，其转变温度在−15 0℃左右，即使在很低的温度下(−1 96℃)，断裂过程中解理断裂占主导地位，裂纹不会立即扩展到整个韧带：宏观上观察到“弹入”扩展，微观断裂模式为准解理断裂。结果表明，裂纹扩展的阻力主要由原始奥氏体晶界、贝氏体团界和贝氏体板条间层间三种势垒构成。这些障碍表现为断裂表面上有凹陷的撕裂脊。在较高温度下，断裂机制以纤维断裂为主，伴随着韧窝断口和一些单独的准解理面。
The fracture behaviour of 8Ni 980 MPa grade high strength steel is investigated by combining experimental results of crack opening displacement (COD) tests at various temperatures with detailed microscopic observations of fracture surfaces and crack configurations in unloaded specimens. The results reveal that this high strength steel possesses high toughness with a transition temperature around −150°C. Even though at a very low temperature (−196°C), cleavage cracking dominates the fracture process and the crack does not propagate immediately through the entire ligament: a ‘pop-in’ extension is observed in macroscopic tests, and the microscopic fracture mode is quasi-cleavage. It is found that resistance to crack propagation is provided by three barriers: original austenite grain boundaries, bainite colony boundaries and interlayers 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 rupture, associated with a ‘dimpled’ fracture surface and some individual quasi-cleavage facets.