摘要
本文概述激光表面熔化工艺的基本原理及其应用。第Ⅰ部分讨论热流计算和显微组织。首先应用一维和三维热流模型的分析解和数值解对激光表面熔化过程中主要工艺参数——冷速、熔区几何参数、温度梯度等进行计算,并与实验结果作比较。对数学模型的适用范围以及对流的影响作了讨论。其次概述了激光表面熔化区显微组织生成的有关理论——凝固热力学、非平衡状态层次、成分过冷判据和绝对稳定性判据和溶质扩散控制的凝固等。
This paper reviews basic principles and applications of laser surface melting.In part Ⅰ, heat flow calculation and microstructure are described.First,main processing parameters in laser surface melting,i.e.cooling rates,geometric parameters of melted zones,tempe- rature gradients and etc.are predicted by analytical and numerical solutions of 1-D and 3-D heat flow models.The theoretical value of processing parameters are compared with experimental values.The validity of mathematical models and the effect of convection are discussed.Subsequently,theories related to the formation of microstructure in laser melted zones-thermodynamics in solidification,hierarchy of non-equilibrium,the constitutional supercooling criterion and the absolute stability criterion,solidification controlled by sol- ute diffusion are outlined.
