40Cr/Q345B双金属热压缩组织演变与界面结合机制

对40Cr/Q345B双金属材料在变形温度为1000、1050、1100和1150℃,变形前保温时间为30和60 min,压下量为50%、65%和80%的条件下进行热压缩复合实验,研究其界面结合行为。借助光学显微镜和能谱仪,研究界面的组织演变及元素扩散规律,利用显微硬度仪分析界面处的显微硬度分布,揭示双金属界面的结合机理。结果表明:在变形温度为1000~1150℃时,变形温度升高有利于40Cr/Q345B双金属的界面结合;压下量从50%增加至65%,促进了界面结合,但压下量为80%时,过高的变形量会影响界面两侧基体的协调性能,从而降低界面的结合强度;此外,变形前保温时间为30 min,有利于界面结合。随着保温时间的增加,基体的晶粒尺寸变大、显微硬度降低,界面处的显微硬度最低,为150 HV;随变形温度的升高,界面处的显微硬度提高,最高为185 HV。40Cr/Q345B双金属热压缩过程中的元素扩散以Cr为主,在变形前保温时间为30 min、变形温度为1150℃下,压下量为50%时的扩散距离约为3.7μm,其结合机制主要为冶金结合。

Microstructure evolution and interface bonding mechanism on 40Cr/Q345B bimetal in hot compression

The hot compression bonding experiments of 40Cr/Q345B bimetal was conducted under the conditions of deformation temperatures of 1000,1050,1100 and 1150 ℃,holding time of 30 and 60 min before deformation,and reduction of 50%,65% and 80%,and its interface bonding behavior was studied. Then,the interfacial microstructure evolution and element diffusion law were studied by optical microscopy(OM) and energy disperse spectroscopy(EDS),and the hardness distribution on the interface was analyzed by micro-hardness tester to reveal the interfacial bonding mechanism of bimetal. The results show that the interfacial bonding of 40Cr/Q345B bimetal is improved with the increasing of deformation temperature at 1000-1150 ℃,and the reduction increases from 50% to 65% which contributes to the interface bonding. When the reduction is 80%,the excessive deformation affects the coordination performance of the matrix on both sides of interface to reduce the bonding strength of interface. In addition,the holding time of 30 min before deformation is also beneficial to interface bonding. As the holding time increases,the grain size of the matrix becomes larger and the hardness decreases to the minimum value of 150 HV on the interface. However,with the increasing of deformation temperature,the hardness at the interface increases,and the maximum value is 185 HV. In the hot compression process of 40Cr/Q345B bimetal,Cr is the main diffusion element,and the diffusion distance is approximately 3. 7 μm under the holding time of 30 min before deformation,the reduction of 50% and the deformation temperature of 1150 ℃ . Thus,the bonding mechanism is mainly metallurgical bonding.