超声作用阶段及形式对熔池晶粒结晶的影响

Effect of different ultrasonic action stages on grain crystallization in TIG weld pool

关键词:  熔池|超声作用|晶粒细化|铝锂合金

Key words:  weld pool|ultrasonic action|grain refinement|aluminum lithium alloy

摘要:

理解不同超声作用下的熔池晶粒结晶特点对超声辅助TIG焊接工艺的优化具有重要意义. 以铝锂合金为研究对象，改变超声作用阶段及施加形式，分析焊缝晶粒分布特征. 结果表明，电弧熄灭后超声作用下，焊缝边缘为断裂的柱状晶，焊缝中心为等轴晶；熄弧前及熄弧后均有超声作用时，焊缝内部全部为等轴晶. 持续超声形式和瞬态超声形式对熔池晶粒结晶具有不同的作用，持续超声主要促进熔池内晶粒的异质形核而促使等轴晶形成，瞬态超声主要通过破碎枝晶细化晶粒. 超声细化铝锂合金TIG焊缝晶粒机制与超声作用阶段及形式具有直接联系.

Abstract:

The mechanism of the grain crystallization in TIG weld pool under different ultrasonic action is of great significance for optimizing the ultrasonic assisted TIG welding process. The grain distribution characteristics in the weld of aluminum-lithium alloy is analyzed by changing the ultrasonic action stage and style.The results showed that the edge of the weld is the broken columnar grain and the center of the weld is equiaxed grain with the ultrasonic action imposed after the arc is extinguished. The grain is equiaxed grain when the ultrasonic action is acted during whole welding process. Continuous ultrasonic action and transient ultrasonic action have different effects on crystal crystallization. Continuous ultrasonic action mainly promotes heterogeneous nucleation of grains in weld pool for the formation of equiaxed crystal. Transient ultrasonic action mainly broken dendrites. Ultrasonic refinement mechanism of the grain structure in the TIG weld of Al-Li alloy is directly related to the stage of ultrasonic action.