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通过X射线衍射、扫描电镜和透射电镜等手段,研究冷拔过程中304HC不锈钢钢丝马氏体相变规律,并对马氏体相变过程中材料的断裂机理进行研究。结果表明,实验用钢形变马氏体的最高转变温度为57.9℃,镍当量为18.7%,满足形变诱导马氏体相变的温度条件和材料条件;随着马氏体相变的进行,试样的抗拉强度增加,延伸率下降;形变诱导马氏体相变的形核位置在孪晶与马氏体的交界面,位错弯曲缠结,形变孪晶协调变形,α′-马氏体在剪切带处切变形核,聚集形成马氏体板条;随着马氏体转变量增加,试样断裂类型由韧性断裂逐渐变为混合断裂;同时,在载荷较小时材料中的Al2O3夹杂与基体分离或本身开裂而形成微孔,随着载荷的增加,碳化物第二相阻碍位错运动并引起应力集中,变形不协调导致微孔长大、聚合,最终形成宏观裂纹。
The martensitic transformation of 304HC stainless steel wire during cold drawing was studied by means of X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The fracture mechanism of the material during martensitic transformation was also studied. The results show that the maximum transformation temperature of martensite in experimental steel is 57.9 ℃ and the nickel equivalent is 18.7%, which meets the temperature and material conditions of the deformation-induced martensitic transformation. With the progress of martensitic transformation, Like tensile strength increases and elongation decreases; deformation-induced martensitic transformation of the nucleation site at the interface between the twin and martensite, dislocation bending entanglement, twin deformation deformation coordination, α’-Markov At the shear zone, the shear-deformed nuclei are aggregated to form martensite laths. With the increase of the martensitic transformation volume, the specimen fracture type gradually changes from ductile fracture to mixed fracture. At the same time, when the load is small, Al2O3 Inclusions separate from the matrix or form cracks in the pores. As the load increases, the second phase of the carbide obstructs the dislocation movement and causes stress concentration. The uncoordinated deformation causes the micropores to grow and polymerize, eventually forming macro-cracks.