摘要
本文通过对激光表面合金成分在微观上的不均匀性的实验研究,着重从理论上探讨了产生表面合金成分在微观上不均匀的内在原因。理论分析表明:在激光辐射作用下,合金熔池内的物质迁移对流过程受到许多因素的影响和制约。这些因素包括合金元素对熔体的表面张力和粘度的影响,合金元素之间的交互作用,合金熔体的熔点变化,即温度梯度变化以及激光合金化工艺。正是上述因素改变了合金熔体的对流特征,从而成为导致表面合金成分不均匀的潜在根源。另外,在合金熔池内,对流驱动力分布的非一致性造成了合金熔体在其横截面内的对流程度和强度的非一致性,最终大大影响了表面合金的成分均匀性。最后,本文指出:通过适当的工艺控制,可以获得在微观上浓度分布均匀的表面合金。
In this paper,the experimental results are studied about micro-heteroge-neous distribution of component of surface alloying which is made by laser.Meanwhile,inherent causes which cause the component of the surface alloy tobecome microscopiclly heterogeneous are studied theoretically.The analysisshows that,considering the effect of laser irradiating,many factors willaffect and confine the process of the mass transfer in molten pool.Thesefactors include the effect of alloying elements on surface tension andviscosity of the melt,and melting point of the melt,as interaction among al-loying elements and the parameters of laser alloying.It is these factors thatchange the convection characteristic of the melt,therefore,they bring thecomponent heterogeneity of surface alloying.On the other hand,in molten pool,the heterogeneity of distribution of convection driving force makes the he-terogeneity of convection extent and intensity in cross-section of the melt,ofcourse,it will affect greatly the component homogeneity of the alloy.Finally,it is pointed out that surfce alloying of the microscopic concentrationhomogeneity can be obtained by approriate technique control.
