Deformation of single and multiple laser peened TC6 titanium alloy

• Published in: Optics and laser technology 2018-03, Vol.100, p.309-316
• Main Authors: Umapathi, A., Swaroop, S.
• Format: Article
• Language: English
• Subjects: Adiabatic flow; Compressive properties; Deformation; Heating; Laser peening without coating; Lasers; Microhardness; Microstructure; Neodymium lasers; Residual stress; Semiconductor lasers; Shot peening; Softening; Stress analysis; Synchrotron radiation; TC6 alloy; Titanium alloys; Titanium base alloys; YAG lasers
• ISSN: 0030-3992; 1879-2545
• DOI: 10.1016/j.optlastec.2017.10.022

•Laser peening without coating done on TC6 (variable power densities and multiple peening).•Softening (of α phase) noticed after 6 GW cm−2(single peening) and 3 passes (multiple peening).•α to β phase transformation accompanied softening, confirmed by synchrotron radiation and microscopy. Laser peening without coating (LPwC) was done on the titanium TC6 alloy at a wavelength of 532 nm using an Nd:YAG laser. The laser power densities of 3, 6 and 9 GW cm−2 were used to peen the samples. Samples were also peened multiple times (1, 3 and 5 passes) at 6 GW cm−2. Microhardness showed an overall 23% increase from the baseline value. Further, softening of α phase in the bulk was observed above 6 GW cm−2 in the samples peened once and above 1 pass in multiply peened samples. A similar trend was observed from the residual stress analysis of the samples. The maximum compressive residual stress was −1780 MPa at a depth of 50 μm at 9 GW cm−2. The observed softening of α phase was proposed due to adiabatic heating. Microstructural changes due to adiabatic heating resulting in increased β volume fractions were observed and confirmed by synchrotron radiation measurements.