Cyclic Deformation Behavior and Its Optimization at Elevated Temperature

Abstract

Recently, low-weight components are particularly required for environmental, ecological and economical aspects. Therefore, light-weight metals/alloys are frequently mentioned and selected for many applications where low density and high strength to weight ratios are an important consideration. Consequently, development and improvement in the field of light-weight alloys can be seen continuously for advanced applications in automotive as well as aerospace industries, where many applications involved about elevated temperature are increase. One of the most important light-weight metals is aluminium and its alloys which possess many attractive characteristics including excellent corrosion resistance in most environments, reflectivity, high strength and stiffness to weight ratio, good formability, weldability and recycling potential. Certainly, these advantageous properties make them ideal candidates to replace heavier materials (steel or copper) for several industries. Therefore, mechanical behaviour of aluminium alloys becomes more and more important, especially under cyclic loading at room and elevated temperature due to failures occurring in machinery components are almost entirely fatigue failures. Accordingly, cyclic deformation behaviour of aluminium alloys was investigated and also improved by wellknown mechanical surface treatments, e.g. shot peening, deep rolling and laser shock peening. Deep rolling is one of the most well-known mechanical surface treatment methods and exhibits a great depth of near-surface work hardening state and compressive residual stresses serving to inhibit or retard fatigue crack initiation as well as crack growth (Scholtes, 1997; Wagner, 1999; Schulze 2005). However, the outstanding benefits of the deep rolling treatment are insecure under high-loading and/or elevated temperature conditions due to occurring relaxation of near-surface macroscopic compressive residual stresses as well as work hardening states. In this case, a detrimental effect on the fatigue lifetime can be expected, particularly in smooth, soft and mechanically surface treated materials, such as deep rolled aluminium alloys because their fatigue lifetime depends significantly on the stability of near-surface compressive residual stresses as well as work hardening states (Altenberger, 2003). Therefore, the main purpose of this research is to investigate systematically the cyclic deformation behavior of the deep rolled aluminium alloys at room and elevated temperature. Wrought aluminium alloys AA5083 and AA6110 were selected