【摘要】 通过不同热处理或热机械处理工艺获得了共析钢的4种不同组织,即2种片层间距的珠光体,球化珠光体以及超细晶(α+θ)复相组织。利用室温单轴拉伸实验、SEM及TEM分析了组织状态对共析钢力学性能和塑性失稳行为的影响,结果表明:细化片层间距可以改善片层珠光体组织的协调变形能力并提高强度,均匀伸长率有所降低的同时总伸长率提高。细片层珠光体的拉伸变形失稳符合塑性失稳判据,但不同片层间距的片层珠光体拉伸断裂均属于准解理断裂。与片层珠光体组织相比,球化珠光体和超细晶(α+θ)复相组织的协调变形能力强,虽然在均匀塑性变形阶段均存在少量渗碳体粒子开裂的情况,但拉伸变形失稳均符合塑性失稳判据,拉伸断裂为韧性断裂。与片层珠光体和球化珠光体相比,超细晶(α+θ)复相组织具有较好的强度-塑性配合。更多还原

【Abstract】 Four different microstructure of eutectoid steel was obtained by different heat treatments or thermo-mechanical treatments: coarse lamellar pearlite,fine lamellar pearlite,spheroidized pearlite and ultrafine( α + θ) duplex structure. The mechanical properties and the plastic instability behaviors of the eutectoid steel with different microstructure were analyzed by means of room-temperature uniaxial tensile tests,scanning electronic microscopy and transmission electron microscopy. The results indicate that reducing the interlamellar spacing could improve the coordinated deformation capability of lamellar pearlite and increase its strength,although results in the decrease of the uniform elongation but leads to the increase of the total elongation. The instability of tensile deformation of fine lamellar pearlite meets the plastic instability criterion,but the tensile fracture of lamellar pearlite with different interlamellar spacings belongs to qusi-cleavage fracture. The coordinated deformation capability of spheroidized pearlite and ultrafine( α + θ) duplex structure are superior to that of lamellar pearlite. Although there are some cracked cementite particles in the stage of uniform plastic deformation,the instability of tensile deformation of spheroidized pearlite or ultrafine( α + θ) duplex structure meets the plastic instability criterion and the tensile fracture of them belongs to ductile fracture. In comparison with lamellar pearlite and spheroidized pearlite,ultrafine( α + θ) duplex structure demonstrates good balance of strength and ductility.更多还原