C.M. Cepeda-Jiménez

Accumulative roll bonding of 7075 aluminium alloy at high temperature

The 7075 Al alloy was processed by accumulative roll bonding (ARB) at 300, 350 and 400 °C. The microstructure and texture were characterized and the hardness was measured. Cell/(sub)grain sizes less than 500 nm and typical β-fibre rolling texture were observed in the three ARBed samples. At 400 °C, the presence of elements in solid solution leads to a poorly misoriented microstructure and to a homogeneous β-fibre texture. At 300 and 350 °C highly misoriented microstructure and heterogeneous β-fibre rolling texture are observed, especially at 350 °C, wherein the degree of dynamic recovery is higher. Hardness of the ARBed samples is affected by the amount of atoms in solid solution at the different processing temperatures.

Simulation of Hot Rolling Processing of an Al-Cu-Mg Alloy by Torsion Tests

Hot torsion tests to fracture to simulate thermomechanical processing were carried out on a solution-treated Al-Cu-Mg alloy (Al 2024-T351) at constant temperature. Torsion tests were conducted to failure in the range 270 to 470°C, between 2 and 26 s-1. A peak ductility of the 2024 alloy was found at about 410°C. The high temperature data was analyzed by means of a Garofalo equation, obtaining a stress exponent of 6.1 and an activation energy for deformation of 180 kJ/mol. These high temperature deformation parameters correspond to an underlying deformation mechanism of constant substructure (n=8) but experiencing increasing microstructure coarsening with increasing temperature. The workability of the alloy was characterized by maximum energy efficiency and stability maps constructed from the torsion tests data to determine optimal conditions for the forming process, which depend on applied strain rate. A forming temperature of about 400°C is recommended.

Fracture toughness for interfacial delamination of Cr-Mo steel multilayer laminate

Abstract Interface toughness for delamination has been determined in a laminate composite consisting of Fe–0·9Cr–0·5Mo steel layers. Three point bend tests were used to evaluate the critical energy release rate G c for delamination under elastic linear and plane strain conditions. A value of G c of 2·8 kJ m−2 was obtained which is considerably lower than the energy for crack propagation across the layer. The given G c corresponds to a critical stress intensity factor K c of 25 MPa m1/2. These low values are responsible of delamination and, therefore, of the 34% improvement in toughness of the laminate with regard to the monolithic material.