超声波冲击技术对AA6061-T6空蚀行为的影响

Effects of Ultrasonic Impact Technology on Cavitation Erosion Behavior of AA6061-T6

AA6061-T6铝合金因较高的比强度、良好的可成型性广泛应用于汽车工业中,但较差的空蚀性能极大的降低了其使用寿命。利用超声波冲击技术在AA6061-T6表面制备了塑性形变强化层,研究塑性形变强化层的微观组织、残余应力及显微硬度分布和抗空蚀性能。结果表明,超声波冲击强化后铝合金表面择优取向由原始的(200)转变为(111),并形成约140μm塑性变形层。与未强化试样相比,强化试样表面显微硬度提高了80.7%,并形成140μm硬化层;表面植入残余压应力达到-259 MPa,残余压应力层深达到700μm。超声波冲击强化处理后的空蚀性能提高2.36倍;空蚀表面形貌分析表明强化后试样空蚀机制由韧性断裂转变为脆性断裂和疲劳破坏。研究表明超声波冲击强化后试样表面晶粒细化、择优取向转变、硬度提高以及较高残余压应力等增强了材料的抗空蚀性能。

AA6061-T6 aluminum alloy is widely used in the automobile industry due to its high specific strength and good formability,but its poor cavitation corrosion performance greatly decreases its service life.A plastic deformation layer was prepared by ultrasonic impact technology(UIT).The microstructure,residual stress,micro-hardness distribution and cavitation erosion resistance of the plastic deformation strengthening layer are investigated.Results show that the preferred orientation of the aluminum alloy surface changed from(200)to(111)after UIT,and a 140μm plastic deformation layer was formed.The surface micro-hardness of UIT sample increased about 80.7%and formed a 140μm hardened layer.The surface residual stress of UIT sample was-259 MPa,and the depth of the residual compressive stress layer reached 700μm.The cavitation erosion performance after UIT is increased by 2.36 times.The analysis of cavitation surface morphology shows that cavitation erosion mechanism of UIT sample changes from ductile fracture to brittle fracture and fatigue failure.Research have proved that the surface grain refinement,preferred orientation transformation,micro-hardness increase and higher residual compressive stress of UIT samples enhance cavitation resistance of the material.