超声振动对CMT电弧增材制造铝合金组织与性能的影响

为减少电弧增材制造铝合金中的气孔及粗大晶粒,采用超声振动辅助CMT电弧增材制造的方法堆焊4043铝合金薄壁件,研究了超声振幅对沉积态材料微观组织及力学性能的影响。研究发现,熔池内部枝晶在超声振动的作用下发生破碎,使得熔池内部液态金属形核率增大,细化晶粒,粗大柱状晶粒也在熔池振动搅拌下转变为细小等轴晶粒。与未使用超声振动辅助的试样相比,平均晶粒尺寸减少了22.5%。同时超声振动引起的空化及声流效应使得试样中气孔尺寸以及数量减小。但随着超声振幅的增加,熔池内部的能量逐渐加大,热输入的增加也使得晶粒发生粗化现象。过大的超声能量破坏了焊缝的结构完整性,导致焊缝内部出现孔洞。施加超声振动试样的抗拉强度较未施加时上升了8.2%~16.3%,且随着超声振幅的增大,抗拉强度及断后伸长率的各向异性逐渐减小。

Effect of ultrasonic vibration on microstructure and properties of aluminum alloy produced by CMT wire arc additive manufacturing

In order to reduce the pores and coarse grains in the aluminum alloy produced by arc additive manufacturing, the method of ultrasonic vibration assisted CMT (cold metal transfer) arc additive manufacturing was used to accumulate the thin-walled parts of 4043 aluminum alloy, and the effect of ultrasonic amplitude on microstructure and mechanical properties of the deposited material was studied. The results show that the aid of ultrasonic vibration breaks dendrites and promotes the formation of more nuclei to refine the grains. The columnar grains are also transformed into fine equiaxed grains under the vibration and stirring of the molten pool. Compared with the specimens without ultrasonic vibration, the average grain size is reduced by 22.5%. At the same time, the cavitation and acoustic flow effects caused by ultrasonic vibration reduce the size and number of pores in the specimens. However, as the ultrasonic amplitude increases, the energy inside the molten pool gradually increases, and the increase in heat input also causes the grains to coarsen. At the same time, excessive ultrasonic energy also destroys the structural integrity of the weld, resulting in holes in the weld. The tensile strength of the specimen with ultrasonic vibration is increased by 8.2%-16.3% compared with that of the specimen without ultrasonic vibration, and the anisotropy of the tensile and elongation gradually decreases with the increases of amplitude.