Abstract
The Ti6Al4V parts produced by the existing selective laser melting (SLM) are mainly confronted with poor surface finish and inevitable interior defects, which substantially deteriorates the mechanical properties and performances of the parts. In this regard, ultrasonically-assisted machining (UAM) technique is commonly introduced to improve the machining quality due to its merits in increasing tool life and reducing cutting force. However, most of the previous studies focus on the performance of UAM with ultrasonic vibrations applied in the tangential and feed directions, whereas few of them on the impact of ultrasonic vibration along the vertical direction. In this study, the effects of feed rate on surface integrity in ultrasonically-assisted vertical milling (UAVM) of the Ti6Al4V alloy manufactured by SLM were systemically investigated compared with the conventional machining (CM) method. The results revealed that the milling forces in UAVM showed a lower amplitude than that in CM due to the intermittent cutting style. The surface roughness values of the parts produced by UAVM were generally greater than that by CM owing to the extra sinusoidal vibration textures induced by the milling cutter. Moreover, the extra vertical ultrasonic vibration in UAVM was beneficial to suppressing machining chatter. As feed rate increased, surface microhardness and thickness of the plastic deformation zone in CM raised due to more intensive plastic deformation, while these two material properties in UAVM were reduced owing to the mitigated impact effect by the high-frequency vibration of the milling cutter. Therefore, the improved surface microhardness and reduced thickness of the subsurface deformation layer in UAVM were ascribed to the vertical high-frequency impact of the milling cutter in UAVM. In general, the results of this study provided an in-depth understanding in UAVM of Ti6Al4V parts manufactured by SLM.
Highlights
Titanium alloy Ti6Al4V has been widely applied to aviation, aerospace, chemical, and biomedical industries due to its superior mechanical properties and chemical inertness [1]
4.1 Effect of Feed Rate on Milling Forces In ultrasonically-assisted vertical milling (UAVM), the high-frequency vibration of the milling cutter in the vertical direction can be taken as the forced simple harmonic vibration in the Z-axis, while the constant rotating movement of the cutting edge can be regarded as uniform linear motion along the Y-axis within a relatively short time and distance
5 Conclusions In this study, comparative experiments of conventional machining (CM) and UAVM were performed on the effects of feed rate on surface integrity of the selective laser melting (SLM)-built Ti6Al4V alloy
Summary
Titanium alloy Ti6Al4V has been widely applied to aviation, aerospace, chemical, and biomedical industries due to its superior mechanical properties and chemical inertness [1]. (2021) 34:67 these drawbacks of SLM, the surface quality of a critical structural part substantially influences the service performances of the part, especially under conditions of high temperature, complex stress loads, and other extreme environments. In this regard, the parts built by SLM still need to be machined to eliminate the surface unevenness for better mechanical properties and service performances
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