The Strengthening Effect of Phase Boundaries in a Severely Plastically Deformed Ti-Al Composite Wire

An accumulative swaging and bundling technique is used to prepare composite wires made of Ti and an Al alloy. These wires show reasonable higher yield stresses than expected from the pure material flow curves. The additional strengthening in the composite is analyzed using nanoindentation measurements, tensile testings and investigations of the microstructure. In addition, these properties are analyzed in relation to the fracture surface of the mechanically tested wires. Additional strengthening due to the presence of phase boundaries could be verified. Indications for residual stresses are found that cause a global hardness gradient from the center to the wire rim. Finally, the yield stress of the wires are calculated based on local hardness measurements

Microstructure and Mechanical Properties of Accumulative Roll-Bonded AA1050A/AA5005 Laminated Metal Composites

Laminated metal composites (LMCs) with alternating layers of commercial pure aluminum AA1050A and aluminum alloy AA5005 were produced by accumulative roll-bonding (ARB). In order to vary the layer thickness and the number of layer interfaces, different numbers of ARB cycles (4, 8, 10, 12, 14 and 16) were performed. The microstructure and mechanical properties were characterized in detail. Up to 8 ARB cycles, the ultrafine-grained (UFG) microstructure of the layers in the LMC evolves almost equally to those in AA1050A and AA5005 mono-material sheets. However, the grain size in the composites tends to have smaller values. Nevertheless, the local mechanical properties of the individual layers in the LMCs are very similar to those of the mono-material sheets, and the macroscopic static mechanical properties of the LMCs can be calculated as the mean value of the mono-material sheets applying a linear rule of mixture. In contrast, for more than 12 ARB cycles, a homogenous microstructure was obtained where the individual layers within the composite cannot be visually separated any longer; thus, the hardness is at one constant and a high level across the whole sheet thickness. This results also in a significant higher strength in tensile testing. It was revealed that, with decreasing layer thickness, the layer interfaces become more and more dominating

Annealing behavior of accumulative roll bonding processed aluminum composites

Accumulative roll bonding (ARB) is an effective method to produce ultrafine‐grained (UFG) sheet materials with high strength. In this work, the ARB process up to five cycles was performed to the starting materials AA1050 and AA6061 and produced three different laminates: AA1050/AA1050, AA6061/AA6061, and AA1050/AA6061. The grain size of AA1050 and AA6061, in all laminates, was reduced significantly after ARB deformation. Meanwhile, a remarkable enhancement in the hardness was achieved. The materials were annealed at different conditions and the microstructures and mechanical properties of the materials were investigated. Static annealing was carried out at temperatures of 100–400°C for 30 min in order to examine the thermal stability of the aluminum alloy. The grain size and hardness evolution of both the AA1050 and AA6061 alloys, in all the three laminates, showed a similar change with the annealing temperature. Annealing induced hardening was observed at 100° C for all the materials examined, and the microstructure of the alloys stayed almost the same as the as‐deformed alloys. The materials softening started after annealing at 150°C, and the hardness decreased rapidly between 150 and 300°C and then stayed stable. The change of the hardness values with the annealing time at low temperature was nearly negligible. The hardness and grain size values of the AA1050 and AA6061 in both the monotonic laminates and composite are similar