TY - CHAP A1 - Noster, Ulf A1 - Altenberger, Igor A1 - Ritchie, Robert O. A1 - Scholtes, Berthold ED - Wagner, Lothar T1 - Isothermal Fatigue Behavior and Residual Stress States of Mechanically Surface Treated Ti-6Al-4V: Laser Shock Peening vs. Deep Rolling T2 - Shot peening N2 - In this paper, the high-temperature fatigue behavior and residual stress states of a Ti-6Al-4V alloy are investigated after mechanical surface treatment. In particular, the two surface treatments investigated, laser shock peening and deep rolling, were observed to result in significantly different residual stress states. The consequent isothermal fatigue behavior at elevated temperatures, characterized using cyclic deformation curves, are discussed in terms of the stability of the near-surface work hardening and compressive residual stresses. Despite pronounced relaxation of the residual stresses, both laser shock peening and deep rolling led to a significant improvement in the cyclic deformation behavior and, hence, increased fatigue lifetimes at elevated temperatures as compared to untreated materials states. Y1 - 2003 SN - 9783527606580 U6 - https://doi.org/10.1002/3527606580.ch57 SP - 447 EP - 453 PB - Wiley-VCH CY - Weinheim; [Cambridge] ER - TY - JOUR A1 - Nalla, Ravi K. A1 - Altenberger, Igor A1 - Noster, Ulf A1 - Liu, G.Y. A1 - Scholtes, Berthold A1 - Ritchie, Robert O. T1 - On the influence of mechanical surface treatments—deep rolling and laser shock peening—on the fatigue behavior of Ti–6Al–4V at ambient and elevated temperatures JF - Materials Science and Engineering: A N2 - It is well known that mechanical surface treatments, such as deep rolling, shot peening and laser shock peening, can significantly improve the fatigue behavior of highly-stressed metallic components. Deep rolling (DR) is particularly attractive since it is possible to generate, near the surface, deep compressive residual stresses and work hardened layers while retaining a relatively smooth surface finish. In the present investigation, the effect of DR on the low-cycle fatigue (LCF) and high-cycle fatigue (HCF) behavior of a Ti–6Al–4V alloy is examined, with particular emphasis on the thermal and mechanical stability of the residual stress states and the near-surface microstructures. Preliminary results on laser shock peened Ti–6Al–4V are also presented for comparison. Particular emphasis is devoted to the question of whether such surface treatments are effective for improving the fatigue properties at elevated temperatures up to ∼450 °C, i.e. at a homologous temperature of ∼0.4T/Tm (where Tm is the melting temperature). Based on cyclic deformation and stress/life (S/N) fatigue behavior, together with the X-ray diffraction and in situ transmission electron microscopy (TEM) observations of the microstructure, it was found that deep rolling can be quite effective in retarding the initiation and initial propagation of fatigue cracks in Ti–6Al–4V at such higher temperatures, despite the almost complete relaxation of the near-surface residual stresses. In the absence of such stresses, it is shown that the near-surface microstructures, which in Ti–6Al–4V consist of a layer of work hardened nanoscale grains, play a critical role in the enhancement of fatigue life by mechanical surface treatment. KW - Deep rolling KW - Elevated temperature behavior KW - Fatigue KW - Laser shock peening KW - Residual stress KW - Surface treatment KW - Ti–6Al–4V Y1 - 2003 U6 - https://doi.org/10.1016/S0921-5093(03)00069-8 SN - 1873-4936 VL - 355 IS - 1-2 SP - 216 EP - 230 PB - Elsevier ER - TY - CHAP A1 - Altenberger, Igor A1 - Nalla, R. K. A1 - Noster, Ulf A1 - Scholtes, Berthold A1 - Ritchie, Robert O. T1 - On the fatigue behavior and associated effect of residual stresses in deep rolled and laser shock peened Ti-6Al-4V at ambient and elevated temperatures T2 - 2003 TMS annual meeting N2 - Mechanical surface treatments, such as deep rolling, shot peening and laser shock peening, can significantly improve the fatigue behavior of highly stressed metallic components. Deep rolling is an especially attractive technique since it is possible to generate deep, near-surface compressive residual stresses and work hardening while retaining a relatively smooth surface finish. Indeed, this technique is best known for increasing the fatigue strength and lifetime of steel components such as crankshafts. Although most work on deep rolling has been on steels, recently it has also been applied with reasonable success to titanium alloys. Accordingly, in this investigation, we examine the effect of deep rolling on the high-cycle fatigue behavior of Ti-6Al-4V, with particular emphasis on the thermal and mechanical stability of the residual stress states and near-surface microstructures. Preliminary results on laser shock peened Ti-6Al-4V are also presented for comparison. In addition, we examine whether these surface treatments are effective in retaining fatigue strength at the higher temperatures of 300 to 450C. Based on the cyclic deformation and stress/life behavior, together with the X-ray and microstructural observations, it is found that deep rolling can be quite effective in retarding the initiation and initial propagation of fatigue cracks in Ti-6Al-4V at such higher temperatures, despite the almost complete relaxation of the residual stresses at the surface. This clearly implies that, in addition to residual stresses, near-surface microstructures, which in Ti-6Al-4V consist of ultrafine near-surface nanostructures, play a critical role in the enhancement of fatigue lifetimes by mechanical surface treatments. Y1 - 2003 UR - https://www.researchgate.net/publication/273462702_On_the_fatigue_behavior_and_associated_effect_of_residual_stresses_in_deep_rolled_and_laser_shock_peened_Ti-6Al-4V_at_ambient_and_elevated_temperatures SP - 359 PB - The Minerals, Metals & Materials Society (TMS) ER - TY - CHAP A1 - Altenberger, Igor A1 - Noster, Ulf A1 - Scholtes, Berthold A1 - Ritchie, Robert O. ED - Wagner, Lothar T1 - High Temperature Fatigue of Mechanically Surface Treated Materials T2 - Shot peening N2 - Introduction The most well known effect of mechanical surface treatments on metallic materials is the improvement in fatigue properties. It is therefore not surprising that most of the archival literature on mechanical surface treatments, such as shot peening, deep rolling and laser shock peening, deals with the effect of near-surface properties on fatigue behavior. Most of these studies, however, are confined to room temperature fatigue behavior; in comparision, the effect of mechanical surface treatment on fatigue behavior at high temperatures has been rarely investigated [1-5]. The reason for this disparity can be found in the popular belief that fatigue strength improvement by mechanical surface treatments is mainly due to the presence of compressive residual stresses, and since such stresses should anneal out at elevated temperatures, mechanical surface treatments for high temperature applications would appear questionable. However, this view may be over simplistic as there is always a possibility that the residual stresses may be at least partially stable at elevated temperatures [6]; in addition, other factors may be involved, such as the nature of the near-surface microstructure. Accordingly, it is the objective of this study to examine the role of mechanical surface treatments on the high temperature fatigue behavior of several metallic engineering materials. Moreover, it is the aim of this work to clarify what are the critical temperature "thresholds' at which near-surface microstructures and residual stresses become unstable and whether this can explain the observed fatigue behavior. Y1 - 2003 SN - 9783527606580 U6 - https://doi.org/10.1002/3527606580.ch62 SP - 483 EP - 489 PB - Wiley-VCH CY - Weinheim; [Cambridge] ER - TY - CHAP A1 - Altenberger, Igor A1 - Nalla, R. K. A1 - Noster, Ulf A1 - Liu, G. A1 - Scholtes, Berthold A1 - Ritchie, Robert O. ED - Lütjering, G. ED - Albrecht, J. T1 - Effects of Deep Rolling on the Fatigue Behavior of Ti-6Al-4V at Ambient and Elevated Temperatures T2 - Ti-2003 Science and Technology, Proceedings of the 10th World Conference on Titanium, held at the CCH-Congress Center Hamburg, Germany 13-18 July 2003, Vol 1 Y1 - 2003 UR - http://www.titaniumthemetal.org/epub/World-Conference-Proceedings-2003-Section-2/F7E2908C00CB5A5E8414934CBF8702B1/WTC%202003%20Sec%202.pdf SN - 3-527-30306-5 SP - 1059 EP - 1066 PB - Wiley ER - TY - CHAP A1 - Altenberger, Igor A1 - Noster, Ulf A1 - Nalla, R. K. A1 - Ritchie, Robert O. A1 - Scholtes, Berthold T1 - Residual stress relaxation in fatigue of mechanically surface treated materials T2 - Proceedings 132nd Annual TMS Meeting, March 2–6, 2003, San Diego, California Y1 - 2003 UR - https://www.researchgate.net/publication/273462779_Residual_stress_relaxation_in_fatigue_of_mechanically_surface_treated_materials SP - 312 ER -