Abstract
With a view to improving the surface quality of the magnesium (Mg) alloy at a warm temperature, the ultrasonic-assisted warm single-point incremental forming (SPIF) is proposed. The surface quality of the Mg alloy during the warm SPIF is primarily affected by two parts: the orange peel patterns of the non-contact surface and the scratches and adhesive wear of the contact surface. In this work, the surface quality of the AZ31B Mg alloy sheet parts at different forming temperatures and ultrasonic amplitudes is evaluated by examining the surface roughness and topography. The results show that the generation of orange peel patterns is significantly affected by temperature. In addition, scratches and adhesive wear of the contact surface increase with the rising temperature. After applying the ultrasonic vibration (UV), the quality of both the non-contact and the contact surfaces of the parts is significantly improved, but too large ultrasonic amplitude slightly reduces the surface quality. Moreover, the microstructural examination results show that UV has a great effect on dynamic recrystallization and grain refinement, which positively affects surface quality improvement.
Highlights
Mg alloy enjoys the advantages of high specific strength and stiffness, good machinability, good shock absorption, high thermal conductivity, etc
A rough texture, which resembles the shape of an orange peel, is generated on the non-contact surface of the Mg alloy during the warm-assisted single point incremental forming (SPIF) (Fig. 3(a))
The morphology, size, and density of the orange peel patterns are significantly influenced by the forming temperatures and ultrasonic amplitudes
Summary
Mg alloy enjoys the advantages of high specific strength and stiffness, good machinability, good shock absorption, high thermal conductivity, etc. The orange peel patterns are sometimes observed on the non-contact surfaces of formed parts of Mg alloy in the warm SPIF. Zhang et al [14] investigated the effect of the lubricating method on the surface quality between the Mg alloy sheet and tool in warm SPIF and found an association of the adhesive wear to temperature and lubrication method. Sakhtemanian et al [26] investigated the effect of UV-assisted on the SPIF process of St/Ti bimetal sheet at room temperature and showed that ultrasonic vibration decreased the coefficient of friction and refined grains. The effects of the ultrasonic vibration on surface quality, including orange peel and adhesive wear, were examined. The effect of three kinds of lubricants on contact surface quality was analyzed
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