Phase gradient in a laser peened TC6 titanium alloy analyzed using synchrotron radiation

• Published in: Materials characterization 2017-09, Vol.131, p.431-439
• Main Authors: Umapathi, A., Swaroop, S.
• Format: Article
• Language: English
• Subjects: Adiabatic heating; Fatigue; Laser peening without coating; Micro hardness; Residual stress; Synchrotron radiation; TC6 alloy
• ISSN: 1044-5803; 1873-4189
• DOI: 10.1016/j.matchar.2017.07.036

The titanium alloy TC6 was laser peened without coating (LPwC) with a pulsed Nd:YAG laser (1064nm) at power densities of 3, 6 and 9GWcm−2. Microhardness data revealed that hardness does not linearly scale with power density. Residual stress analysis indicated that the profile has two distinct regions, one near surface (100μm) with decreasing compressive residual stresses with increasing power density. Transmission electron microscopy (TEM) showed high dislocation density with dislocation tangles and dislocation walls without dislocation cell or nanocrystals in the near surface region. Synchrotron radiation showed the increase in volume fraction of β phase with increase in power density in the far-surface region. Fatigue performance of the samples (number of cycles to failure) subjected to LPwC at a power density of 6GWcm−2 was found to have increased by a factor of 2–4, in the load range of 12.5–15kN. Further, it was observed that in addition to the normally observed sub-surface crack nucleation of LPwC samples, additional formation of β phase in the far-surface region improves fatigue performance. [Display omitted] •Near-surface region (100μm) with increased volume fraction of β phase•Formation of β phase due to adiabatic heating•Fatigue lives increase by factor of 2–4 in the load range 12.5–15kN.•β phase enhances fatigue life.