1Cr22Mn16N高氮奥氏体不锈钢塑性变形连接中界面组织演化及愈合机制

Evolution and Healing Mechanism of 1Cr22Mn16N High Nitrogen Austenitic Stainless Steel Interface Microstructure During Plastic Deformation Bonding

为解决高氮奥氏体不锈钢焊接难题,以高氮奥氏体不锈钢1Cr22Mn16N为实验材料,采用塑性变形连接技术实现了1Cr22Mn16N的连接。通过OM、EBSD和TEM等手段研究了不同变形参数下的连接界面组织演化,讨论了界面愈合机理,并采用拉伸实验评估了连接接头的结合强度。研究结果表明,随着变形量的增加和变形温度的升高,连接界面的结合程度显著提高。当变形温度达到1200℃,变形量为40%时,连接界面结合较好,其拉伸性能达到基体同等水平。在塑性变形连接过程中,由于热力耦合促使原始粗大的晶粒细化,在连接界面处发生不连续动态再结晶,随后再结晶晶粒核心通过消耗变形晶粒中的应变储能发生长大,诱导连接界面弯曲,晶界迁移;与此同时,位错在应力的作用下堆积和缠结,在界面附近的变形晶粒内形成了大量亚晶界,随着应力的增大发生了连续动态再结晶,使亚晶界转变成大角度晶界,促进了连接界面愈合。高氮奥氏体不锈钢1Cr22Mn16N塑性变形连接过程中,在连续动态再结晶与不连续动态再结晶的协同作用下实现了界面的连接。

High nitrogen austenitic stainless steels(HNASSs)are widely used for their good wear resistance and high strength,plasticity,and corrosion resistance.Among these steels,1Cr22Mn16N HNASS improves the cost effectiveness because of the incorporation of a N element in place of the expensive Ni element.In addition,the overall mechanical properties of the steel are further improved because of the solid solution-strengthening effect of the N element.However,the traditional welding methods such as arc welding,tungsten gas shielded welding,and friction stir welding are not suitable for 1Cr22Mn16N HNASS welding because of the different solubility of N in the liquid and solid phases.N easily spills out during the welding process,which considerably degrades the mechanical properties of the welded joints.Therefore,a new welding method needs to be explored to solve the problems in 1Cr22Mn16N welding.In this work,the bonding technology of plastic deformation was introduced to solve the poor performance problems of 1Cr22Mn16N HNASS welded joints.The experiments were conducted through the Glebble 3500 thermomechanical simulation in the temperature range of 1050-1250℃ and a strain range of 10%-40% with a strain rate of 0.1 s^(−1).The microstructure evolution of the bonding interface was characterized and investigated using OM,EBSD,and TEM;the interface healing mechanism was discussed,and the bonding strength of the joint was evaluated by tensile test.The results show that the bonding level of the interface substantially increases with the increase in deformation and temperature.When the deformation temperature reached 1200℃ and the strain reached 40%,the mechanical properties of the bonding interface reached up to the same level as the matrix.During the process of deformation,discontinuous dynamic recrystallization(DDRX)occurred at the interface because of thermomechanical coupling;meanwhile,dislocations accumulated and entanglement occurred under the action of stress,forming a large number of subgrain boundaries within the original grain boundaries near the interface,which,lead to continuous dynamic recrystallization(CDRX).The healing of the interface was achieved by the synergistic effect of CDRX and DDRX.