层片状珠光体生长形貌的相场法模拟

摘要

采用相场法,以共析钢为例,模拟研究了不同初始共析层片间距及不同初始过冷度条件下层片状殊光体微观组织的生长形貌,探讨了不同初始层片间距及不同初始过冷度条件下层片状珠光体微观组织生长的规律.模拟结果表明:过冷度不变时,随着初始层片间距的增大,共析层片振幅增大,共析层片生长形貌的变化是规则对称的层片状→非规则非对称形状→棒状;层片间距不变,初始过冷度在19.6～20 K时,随着初始过冷度的减小,共析钢中碳原子扩散能力增大,层片间距的失稳,致使共析层片由规则状向非规则形状变化;初始过冷度在20～22 K时,随着初始过冷度的增大,共析钢中碳原子的扩散能力减弱,渗碳体相前沿碳原子浓度无法使其规则对称地生长,渗碳体相向碳原子浓度高的地方生长,从而产生倾斜生长以及层片合并现象.%Taking eutectoid steel as example and using phase-field method,the growth morphology of lamellar pearlite microstructure is investigated simulatively under conditions of different initial lamella spacing and different initial undercooling degree and the growth rule of that microstructure is explored under the same conditions.The simulation result shows that with increase of initial lamella spacing when the undercooling degree is kept constant,the vibration amplitude of eutectoid lamella some will increase and the change of eutectoid lamellar some growth morphology will exhibit as follows:regular symmetric lamellar --→irregular asymmetric one-→rod like one.When the lamella spacing is kept constant and the initial undercooling is in the range from 19.6 K to 20 K,the diffusion ability of carbon atoms in eutectoid steel will increase with the decrease of the initial undercooling degree.Meantime,the stability of lamella spacing will lose,making the eutectoid lamella some change from regular form to irregular form.When the initial undercooling degree is in the range from 20 K to 22 K,the diffusion ability of carbon atoms in eutectoid steel will decrease with the increase of initial undercooling degree,making the concentration of carbon atoms in cementite phase front insufficient to grow regularly and symmetrically,and the cementite phase will grow toward that place where exists high carbon concentration,so that a phenomenon of tilt growth and lamellar merging will occur.