椭圆双向超声振动渐进成形对6061铝合金薄壁件力学性能和微观结构的影响

Influence of Ellipse Bidirectional Ultrasonic Vibration Incremental Forming on Mechanical Properties and Microstructure of 6061 Aluminum Alloy Thin-Walled Parts

摘要:

为了在加工复杂薄壁件的过程中改善其工艺性能和使用性能，对6061铝合金复杂薄壁件双向振动超声渐进成形后的力学性能和微观结构进行了研究，对比了传统渐进成形、垂直单向超声振动渐进成形和椭圆双向超声振动渐进成形工艺，对成形后的试验件进行硬度测试、残余应力分析以及扫描电子显微镜观察，以验证双向渐进成形工艺对铝合金复杂薄壁件成形性能和使用性能的提升效果。硬度试验结果表明，椭圆超声振动渐进成形能够软化材料，增加材料塑性和韧性，从而提高6061铝合金成形复杂薄壁件的能力，试验件断裂面端口产生大量韧窝的现象也进一步证明了这一观点。试验件成形表面的微观形貌特征表明椭圆超声振动渐进成形在改善试验件表面质量方面具有显著优势。此外，发现椭圆超声振动渐进成形方法能够在6061铝合金表面形成残余压应力层，有利于提高薄壁件的抗疲劳性能。

Abstract:

To improve the processing and practical performance during the manufacture of complex thin-walled parts, the mechanical properties and microstructure revolution of complex thin-walled parts of 6061 aluminum alloy prepared by ellipse bidirectional vibration incremental forming were investigated. The traditional incremental forming, vertical unidirectional ultrasonic vibration incremental forming, and ellipse bidirectional ultrasonic vibration incremental forming methods were compared. To verify the enhancement effect on forming quality and mechanical properties of complex thin-walled parts of aluminum alloy, the microhardness and residual stress of as-prepared parts were analyzed, and their morphologies were observed. The microhardness test results show that the ellipse ultrasonic incremental forming process can soften the material and improve its plasticity and toughness, thereby promoting the formability of thin-walled parts of aluminum alloy. A great number of dimples appearing on the fracture surface further confirms this conclusion. The microstructure characteristic on the surface of as-prepared parts shows that the ellipse bidirectional vibration incremental forming method can significantly improve the surface quality. In addition, the ellipse bidirectional ultrasonic vibration incremental forming method can form a residual compressive stress layer on the surface of 6061 aluminum alloy, which improves the fatigue resistance performance of complex thin-walled parts.