In this paper, very systematic experimental data on the orientation dependence of the twinning stress in Cu–8 at.% Al single crystals are reported. A method, typical for ‘latent hardening experiments’, is employed to determine the critical stresses needed to activate twin systems in a dislocated crystal. Results show that activation of a particular twin system follows a critical resolved shear stress law, which is analogous to Schmid's law for slip. A criterion for the onset of twinning in fcc crystals, based on examination of a large body of experimental results, is also formulated. The criterion says that the onset of twinning occurs only when three necessary conditions are met simultaneously: firstly, the ratio τ_RSS /τ_C of the resolved shear stress to the critical stress of a twin system is greater than that of any other slip system; secondly, τ_RSS is greater than a minimum stress necessary for twinning to occur; thirdly, τ_RSS satisfies the sense of a twin shear. Other experimental results related to twinning stress in fcc crystals are also discussed.

This paper presents the results of numerical modelling of the rolling process of aluminum alloy bars in a three-high skew mill. The purpose of the examination was to determine the optimal rolling temperature for this alloy. The numerical examination for aluminum alloy 6005 (AlZn5.5MgCu) was performed using the Forge3^®-2D Plane strain state commercial software. The rheological properties of the examined alloy were determined from uniaxial compression tests done using the metallurgical process simulation system Gleeble 3800. The numerical analysis of the process of rolling 6005 alloy bars in a three-high skew mill was conducted within the temperature range of 150–350 °C and at a deformation of 0.29.

The paper presents an analysis of the results of numerical tests of the extrusion process of structural panels made of the 5xxx and 6xxx series aluminium alloys in a designed split die. The obtained products are intended for innovative superstructures of special car bodies. The main purpose of the research was the designed split die and numerical simulations and analysis of test results to determine the parameters of the extrusion process. The distribution of stress intensity, strain, strain rate, and temperature in the extruded metal was analysed for two different speeds of the punch movement. On the basis of the analysis of the distribution of stress values occurring in the extrusion process, the conditions enabling the real process of extrusion of the panel profile in industrial conditions in the designed split die were determined. It was shown that panel sections can be produced from ingots with a length of 770 mm on a press with a pressure of 35 MN (12”).

The paper presents the results of numerical modelling of the forging process of magnesium alloy ingots on a hydraulic press with the use of flat and shaped anvils. The use of shaped (rhombic-trapezoid) anvils will affect the uniform distribution of temperature and strain intensity in the entire volume of the forging, causing a number of forging passes, which in consequence will reduce the costs of the blank manufacturing process. However, higher values of the strain intensity were obtained during the deformation of the material in flat anvils. The purpose of the research was to propose assumptions for forging technology of producing a blank from AZ91 alloy with the use of flat and shaped anvils. Numerical examination for AZ91 magnesium alloy was carried out using the Forge^®NxT commercial software. The rheological properties of the investigated alloy were determined on the basis of uniaxial compression tests carried out in the Gleeble 3800 metallurgical simulation system. The numerical analysis of the process of forging AZ91 alloy ingots on a press was conducted in the temperature range of 200–400 °C and at several forging passes.