Fatigue strength of Ti6Al4V titanium alloy machined under flood and cryogenic conditions

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Fatigue strength of Ti6Al4V titanium alloy machined under flood and cryogenic conditions

STRAMARE Andrea, BERTOLINI Rachele, BRUSCHI Stefania, GHIOTTI Andrea, CAMPAGNOLO Alberto

Abstract. Ti6Al4V titanium alloy wrought round bars characterized by a fine equiaxed microstructure were machined using two different lubrication strategies, namely traditional water-based cutting fluid and liquid nitrogen. Surface integrity after machining was assessed in terms of (i) sub-surface severe plastic deformation layer, (ii) surface topography, and (iii) residual axial stresses as a function of the distance from the machined surface. Finally, the machined specimens were subjected to fatigue tests on a four-point rotating bending machine. For the two sets of specimens, the Wöhler curves were derived to determine their fatigue strength using the modified staircase method. No remarkable difference in terms of surface topography was found between the flood and cryogenic machined specimens, but the latter were characterized by higher and deeper compressive residual stresses and higher severe plastic deformation layer beneath the machined surface. Despite that, it is shown that the fatigue limit of the flood and cryogenic machined specimens is very similar, as well as crack initiation sites have the same location. An explanation of that can be found in the very fine microstructure of the as-received material, which prevails over the other characteristics induced by any machining strategy.

Keywords
Ti6Al4V, Cryogenic Machining, Surface Integrity, Fatigue Strength

Published online 4/24/2024, 10 pages
Copyright © 2024 by the author(s)
Published under license by Materials Research Forum LLC., Millersville PA, USA

Citation: STRAMARE Andrea, BERTOLINI Rachele, BRUSCHI Stefania, GHIOTTI Andrea, CAMPAGNOLO Alberto, Fatigue strength of Ti6Al4V titanium alloy machined under flood and cryogenic conditions, Materials Research Proceedings, Vol. 41, pp 1935-1944, 2024

DOI: https://doi.org/10.21741/9781644903131-214

The article was published as article 214 of the book Material Forming

Content from this work may be used under the terms of the Creative Commons Attribution 3.0 license. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.

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