Ultrafine‐Grained Laminated Metal Composites: A New Material Class for Tailoring Cyclically Stressed Components

Abstract

Technical components are frequently exposed to cyclic loads. These cyclic stresses are often very small but can result in a severe failure of the material, although the applied stress amplitudes are significantly smaller than the yield value of the material. The phenomenon of material fatigue has been systematically investigated since the nineteenth century. [1,2] Nowadays, cyclically loaded parts are increasingly governed by new light-weight design concepts. Thus, new materials with a high-specific monotonic and cyclic strength come into play. For the prospective use of new light-weight material concepts in engineering applications, it is extremely important to understand the damage mechanisms that occur during cyclic loading in detail. Different approaches to enhance the fatigue life in aluminum-based materials that are cyclically are discussed in the following:One approach to enhance the fatigue life of materials is by increasing the strength of the material. This is often achieved by alloying. [3][4][5][6] However, one major drawback is that the corrosion properties often get worse in the higher alloyed systems, compared with less or unalloyed samples. [7] Another method to enhance the strength is given by grain refinement. The advantage of this method is that the increase in strength is achieved without changing the chemical composition of the material. Particularly effective methods to reduce the grain size up to the submicrometer range are the severe plastic deformation processes. [8][9][10] The materials are subjected to high plastic deformation without changing the cross-sectional shape of the material during these processes. It is possible to introduce a very high amount of plastic deformation and therefore also new dislocations into the material by repeating the process steps several times. These dislocations form new subgrains which transform by further deformation into high-angle grain boundaries as a result of energetic minimization. The cyclic properties of such ultrafine-grained (UFG) materials are significantly better in comparison with their coarse-grained (CG) counterparts. [10][11][12][13] The development of dislocation arrangements and/or structures that typically accommodate strain during fatigue in CG materials is hindered because of the small grain size in UFG materials. [14,15] Another highly interesting method to enhance the fatigue properties is to combine different materials, both in terms of mechanical strength, as well as Young's modulus, to laminated metal composites (LMCs). Fundamental research has been

Residual Stresses in Ultrafine‐Grained Laminated Metal Composites Analyzed by X‐ray Diffraction and the Hole‐Drilling Method

“…[ 16–19 ] These UFG LMCs are characterized by a significantly increased fatigue life both in the LCF and HCF regime compared with CG and UFG monomaterial reference sheets. [ 20 ] This observation has been found and experimentally verified for various LMCs based on different aluminum alloys [ 21,22 ] (homogenous LMCs) as well as for aluminum/steel LMCs [ 23,24 ] (heterogeneous LMCs).…”