Wytwarzanie wielofunkcyjnych blach techniką ścinania

Incremental shear has been used to vary blank properties along the sheet plane. The feasibility of the method has been investigated to manufacture so called Tailor Sheared Blanks featuring property distribution of the blank without thickness variation. Mechanical properties resulting from evolution of coarse grain microstructure towards ultra fine grain one can be achieved. Tool configuration, experimental procedure, simulation using finite element method and preliminary trials of producing tailored blanks by incremental shear were described

Ultrafine grained plates of Al-Mg-Si alloy obtained by Incremental Equal Channel Angular Pressing : microstructure and mechanical properties

In this study, an Al-Mg-Si alloy was processed using via Incremental Equal Channel Angular Pressing (I-ECAP) in order to obtain homogenous, ultrafine grained plates with low anisotropy of the mechanical properties. This was the first attempt to process an Al-Mg-Si alloy using this technique. Samples in the form of 3 mm-thick square plates were subjected to I-ECAP with the 90˚ rotation around the axis normal to the surface of the plate between passes. Samples were investigated first in their initial state, then after a single pass of I-ECAP and finally after four such passes. Analyses of the microstructure and mechanical properties demonstrated that the I-ECAP method can be successfully applied in Al-Mg-Si alloys. The average grain size decreased from 15 - 19 µm in the initial state to below 1 µm after four I-ECAP passes. The fraction of high angle grain boundaries in the sample subjected to four I-ECAP passes lay within 53-57 % depending on the examined plane. The mechanism of grain refinement in Al-Mg-Si alloy was found to be distinctly different from that in pure aluminium with the grain rotation being more prominent than the grain subdivision, which was attributed to lower stacking fault energy and the reduced mobility of dislocations in the alloy. The ultimate tensile strength increased more than twice, whereas the yield strength - more than threefold. Additionally, the plates processed by I-ECAP exhibited low anisotropy of mechanical properties (in plane and across the thickness) in comparison to other SPD processing methods, which makes them attractive for further processing and applications

Joining ultrafine grained aluminium by friction stir welding – processing, microstructure and mechanical properties

Nowadays different processes are used to improve mechanical properties of materials. In metallic materials, grain size refinement down to nanoscale is one of the most efficient strengthening mechanisms, as predicted by Hall-Petch relationship. Such microstructure refinement can be obtained in several ways, among others by severe plastic deformation (SPD). Although a tremendous progress has been made in the development of SPD methods, the main drawback is the restriction in billet dimensions. The most common shape – rods, are manufacturing with diameter about few or sometimes over a dozen millimetres. Incremental ECAP is a novel tool to manufacture plates with ultrafine grained structure. Possible sizes of plates are promising for future applications, e.g. in automotive industry. Another issue related to ultrafine grained materials is joining without losing their properties governed by the nanoscale structure. Traditional methods cause grain coarsening which is highly unwanted. In this work plates from Al 1050 after Incremental ECAP were joined using Friction Stir Welding. The quality of joints was determined using microscopic observations. Also, the structure of joints and base materials was investigated by light microscopy and transmission electron microscopy. Mechanical properties were measured by microhardness and tensile tests. To investigate mechanical properties like yield strength and tensile strength mini samples were used. Samples were separately cut from the joints and initial materials as well. It allowed to investigate the differences in both areas. The results revealed that joints zone are characterized by lower values of microhardness and tensile properties compared to base materials. Structure investigation showed changes in grain sizes caused by joining process