Effect of shot peening on the fatigue and fracture behaviour of two titanium alloys

• Published in: Journal of materials science Vol. 31; no. 22; pp. 5953 - 5960
• Main Authors: SRIDHAR, B. R, RAMACHANDRA, K, PADMANABHAN, K. A
• Format: Journal Article
• Language: English
• Published: Heidelberg Springer 15.11.1996
• Subjects: Applied sciences; Exact sciences and technology; Fatigue; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Metals. Metallurgy; Fatigue life; Rupture; Temperature effect; Mechanical properties; Zirconium alloy; Fatigue; Shot peening; Aluminium alloy; Titanium base alloys; Surface treatment; Stress relaxation; Fractography; Vanadium alloy; Residual stress
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1007/BF01152145

The fatigue and fracture behavior of two titanium alloys, the near-alpha IMI-685 and alpha-beta IMI-318, were studied in the machined and polished (MP) and the machined, polished and shot (glass-bead) peened (MPS) conditions. Glass-bead peening reduced the room-temperature and the high-temperature (450 deg C) fatigue life of alloy IMI-685 at high stress amplitudes, sigma sub a , approaching the proof stress, sigma sub ps , of the material (LCF region). When the applied stress amplitude (0-770 MPa, HCF region) was comparable to the peen-induced peak longitudinal residual stress, sigma sub LP , i.e., ( sigma sub LP / sigma sub a )=0.92, an improvement in the room-temperature fatigue life of IMI-685 was observed. When the ( sigma sub LP / sigma sub a ) ratio was less than this value, decreases in the fatigue life were seen. The room-temperature fatigue behavior of IMI-318 at high stress amplitudes was similar to that of IMI-685. The decreases in the fatigue life of this alloy, at a stress amplitude (770 MPa) where improvement was observed for IMI-685, could be attributed to the higher relaxation of peen-induced residual stresses in IMI-318 compared with IMI-685. Glass-bead peening improved the high-temperature (450 deg C) fatigue life of IMI-685 at a low stress amplitude (465 MPa; ( sigma sub a / sigma sub PS )=0.87). The crack-initiation sites in the MP and the MPS conditions were at the surface for both the alloys. However, fracture in the surface layers of the alloys appeared more brittle in the peened (MPS) rather than in the unpeened (MP) condition.