中文摘要：

利用金相、电子背散射衍射（EBSD）技术结合纳米压痕仪研究了低碳Mn-Mo-Nb-B微合金钢的组织转变、晶粒的晶体学取向及其纳米力学性能.由1℃/s冷速连续冷却到室温所得组织主要是贝氏体铁素体和粒状贝氏体.以1℃/s冷速连续冷却到560℃淬水所得组织为针状铁素体和淬水时形成的马氏体/贝氏体,其中相邻针状铁素体之间为小角晶界;前一试样中.粒状贝氏体的平均纳米压痕硬度（2.31 GPa）与后一试样中针状铁素体的平均纳米压痕硬度（2.22 GPa）极为接近取向差较小的针状铁素体组织在1℃/s冷速下连续冷却过程中碰撞、接合成粒状贝氏体.

英文摘要：

Morphologyies and crystallographic orientations of grains, and nano-mechanical properties of continuous transformation structures in a low carbon Mn-Mo-Nb-B microalloyed steel were studied by using OM, EBSD and nano indentation. The microstructures of the specimen cooled continuously at a rate of 1 ℃ /s to ambient temperature consisted of granular bainite, bainitic ferrite and M/A constituent. While, the microstructure in the specimen cooled continuously to 560 ℃ at rate of 1 ℃ /s then quenched consisted of acicular ferrite and martensite/bainete. The misorientation angles between some nearby acicular ferrites are much low and the nanohardness of granular bainite （2.31 GPa） is rather close to that of acicular ferrite （2.22 GPa）. Hereby, the formation of granular bainite should be through coalescence of several acicular ferrites with the almost same orientation, which formed during continuously cooling at 1 ℃ /s.