基于MD探究划痕速率对单晶FeO/Fe断裂的影响

Effect of scratch rate on FeO/Fe fracture of single crystal studied based on MD

氧化皮的断裂行为及力学性能是影响无酸除鳞工艺参数设定的关键因素。通过分子动力学软件Lammps模拟划痕速率对氧化皮断裂行为的影响,从载荷-位移关系、中心对称参数(CSP)、原子堆积、位错、温度、原子位移矢量、径向分布函数等多角度分析不同划痕速率对单晶FeO/Fe界面分离的影响,并对430不锈钢表面氧化皮进行划痕试验验证。模拟结果表明,随着划痕速率从100 m/s增加至200 m/s,划至相同距离时,法向和切向峰值载荷逐渐增加,FeO/Fe界面处紊乱程度逐渐增大,温度升高,FeO层软化,位错长度及数量、原子键合强度等减小,促进了FeO/Fe界面的分离;试验结果表明,随着划痕速率从0.5 mm/min增加至2.0 mm/min, 430不锈钢氧化皮断裂临界点提前,从距起始点1.26 mm提前至1.05 mm处,断裂临界载荷和结合强度逐渐降低,临界载荷由0.439 N降低至0.362 N,结合强度由15.2 MPa降低至14.1 MPa,与模拟结果趋势相对应。本研究为掌握氧化皮的断裂机理提供理论支撑、为提高无酸除鳞工艺参数设置的精确性提供重要指导。

The fracture behavior and mechanical properties of oxide are the key factors affecting the parameters setting of acid-free descaling process.Molecular dynamics software Lammps was used to simulate the effect of scratch rate on the fracture behavior of oxide scale.The effects of different scratch rates on the separation of FeO/Fe interface were analyzed from the perspectives of load-displacement relationship,CSP,atomic accumulation,dislocation,temperature,atomic displacement vector and radial distribution function,and verified by scratch test on the oxide scale of 430 stainless steel surface.The simulation results show that as the scratch rate increases from 100 m/s to 200 m/s,the normal and tangential peak load gradually increases,the disorder degree at the FeO/Fe interface increases,and the temperature increases when the scratch reaches the same distance,which makes the FeO layer gradually soften,and the length and number of dislocation and atomic bonding strength gradually decrease,promoting the separation of the FeO/Fe interface.Test results show that with the increase of scratch rate from 0.5 mm/min to 2.0 mm/min,the breaking point of 430 stainless steel oxide is advanced from 1.26 mm to 1.05 mm from the starting point,the critical load and bonding strength are gradually reduced,and the critical load is reduced from 0.439 N to 0.362 N.The binding strength decreases from 15.2 MPa to 14.1 MPa,which corresponds to the trend of simulation results.This study provides theoretical support for understanding the fracture mechanism of the oxide scale,and provides important guidance for improving the accuracy of parameter setting for acid-free descaling.