title: Cu/Fe Nanolayered Composites Processed by Accumulative Roll-Bonding (ARB)
Creators: name: Ghanem, Maher
Publisher: name: Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU)
Year: 2025

description: The recorded exceptional mechanical properties of material with grain sizes below 1 μm, lead to increasing interest in the nanocrystalline and ultrafine-grained (UFG) materials, as they show noticeable advantages compared to their larger-grained counterparts. It is determined that they possess significant promise for diverse engineering uses in industries like automotive, aerospace, and medical, particularly for structural components requiring high durability. This study focuses on the application of the Accumulative Roll Bonding (ARB) chosen from the many Severe Plastic Deformation (SPD) methods to process Oxygen-Free Copper (OF-Cu), Copper-Tin (CuSn4), and Iron (Fe) sheet materials. The objective is to create laminated microstructures with ultrafine grains, leading to improved mechanical properties. One notable advantage of the ARB process over other SPD methods is its suitability for large-scale production of ultrafine-grained metal sheets, making it feasible for industrial implementation. Applying ARB method to process metal sheets requires pre-cleaning and wire brushing of the sheets surfaces to eliminate any contaminants and oxide layers, followed by stacking of the sheets in a specified order. Only then the sheets will be rolled together with a ‘to be defined’ thickness reduction that usually is or exceeds 50%. The rolling causes the metal sheets to bond as they undergo significant plastic shear deformation. After approximately 2 to 4 ARB cycles, the ultrafine grained microstructure begins to develop. The present study deals with the production of Cu/Fe laminated metal composites of fcc/bcc system by repeated rolling up to 14 cycles, leading to a minimum layer thickness below 100 nm and then investigates their structure, texture, and corresponding mechanical properties. The samples acquired for testing were cut in the rolling-normal direction (RD-ND) plane. Investigating the structure and texture evolution of the metal composites was accomplished using Scanning electron microscope in backscatter mode (SEM-BSE) and electron backscattering diffraction imaging (EBSD). Nanoindentation experiments following the continuous stiffness method (CSM) were used for determining the individual layers hardness. Uniaxial tensile tests were conducted at room temperature at a constant engineering strain rate of 10-3 s-1. The evolution and differences in strength after various ARB cycles are discussed in detail. The lamellar microstructure of these heterogeneous nanoscale composites was quite homogeneous over the whole sample volume and is retained also after thermal annealing between 500 to 700 °C which shows that nanomaterials with exceptional thermal stability have been obtained. Furthermore, the nanolaminates exhibit exceptional strength, with the ultimate tensile strength (UTS) increasing proportionally to the number of ARB cycles. The nanolaminates of Cu/Fe and CuSn4/Fe, show two-step strengthening regime before and after the 10th ARB cycles. Different models to describe the strengthening behavior are mentioned.