为了掌握微合金高强度低碳贝氏体钢中不同强化方式的贡献大小,采用正电子湮没技术、透射电子显微镜及扫描电子显微镜分析了该钢热轧和回火处理后的显微组织、位错密度及第二相粒子的形貌及尺寸,对其屈服强度进行了定量计算,并采用多功能材料试验机对该钢的力学性能进行了测试.结果表明:该钢的位错密度约为2.65 × 1014 m-2,位错强化是该钢主要的强化方式,对屈服强度的贡献值约327 Mpa,占其屈服强度的41.3%;该钢中存在大量细小弥散的球状或近球状的(Ti,Nb)(C,N)第二相粒子,其尺寸多在10 nm以下,析出强化对屈服强度的贡献值约为172 Mpa,占屈服强度的21.7%;固溶强化和间隙原子强化的贡献值分别约为129 Mpa和94 Mpa,分别占屈服强度的16.3%和11.9%;理论计算值与实测值基本吻合.
In order to learn the contribution of different reinforcement modes, after hot rolling with mill and tempering, the microstructure, dislocation density, second phase morphology and size of low carbon bainitic steel were investigated by using SEM, TEM and positron annihilation technology. The yield strength was quantitatively calculated. The mechanical properties of the tested steel were determined by using multi-function material testing machine. The results show that the dislocation density was about 2. 65 × 1014 m-2. Dislocation strengthening which was the main mode contributed 327 MPa to the yield strength, which accounted for 41. 3% of the yield strength. A large number of fine spherical and near-spherical (Ti,Nb)(C,N) second phase particles were observed and the size of most particles was less than 10 nm, which contributed 172 MPa to the yield strength and accounted for 21.7%. Solution strengthening and interstitial atom strengthening contributed 129 MPa and 94 MPa to the yield strength, which accounted for 16. 3% and 11.9% respectively. The strength value calculated by the strengthening mechanism model was very close to the measured value.
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