Mechanical behaviour of ultrafine grained Al-Mg alloys obtained by different processing routes

Abstract

The subject of the study were microstructure and mechanical properties of two commercial 5xxx aluminium alloys obtained by Plastic Consolidation (PC) of nanopowders and Hydrostatic extrusion (HE). It has been observed that HE samples exhibit a higher strength whereas PC samples higher ductility. The two types of samples also differ in the type and intensity of serrations on stress-strain curves. The microstructures of samples processed were found to differ significantly in terms of size and shape of grains, grain boundary characteristics, second phase particles content and density of dislocations. The results are discussed in terms of the influence of microstructure on mechanical behaviour of 5xxx aluminium alloys processed by severe plastic deformation.Keywords: Transmission Electron Microscopy, Portevin-Le Chatelier effect, Strengthening mechanisms, Ultrafine grained W poniższej pracy badano właściwości mechaniczne dwóch komercyjnych ultra drobnoziarnistych stopów aluminium serii 5xxx otrzymanych przez Konsolidację Plastyczną (PC) nanoproszków oraz przez Wyciskanie Hydrostatyczne (HE). Mikrostruktury badanych próbek znacząco się różniły, w szczególności pod względem wielkości ziarna i charakteru granic ziaren. Badania właściwości mechanicznych pokazały, że obie próbki wykazują znakomite właściwości wytrzymałościowe (w obu próbkach granica plastyczności przekracza 450 MPa), jednakże próbki HE wykazują wyższą wytrzymałość, podczas gdy próbki PC większą plastyczność. Wyniki przedstawiono w formie analizy wpływu mikrostruktury na właściwości mechaniczne stopów aluminium serii 5xxx otrzymanych technikami dużego odkształcenia plastycznego. Wysokie właściwości mechaniczne przypisano różnorodnym mechanizmom umacniającym i funkcjonującym w tych próbkach, włączając w to: umocnienie roztworowe, umocnienie wydzieleniowe oraz umocnienie granicami ziaren i dyslokacyjne. Uzyskane wyniki wskazują na to, że mikrostruktura ma znaczący wpływ nie tylko na właściwości mechaniczne, ale również na typ ząbkowania na krzywych rozciągania.

Microstructure and Mechanical Properties of Spark Plasma Sintered and Severely Deformed AA7075 Alloy

“…Considerable strain is made using workpiece SPD technologies such as high-pressure torsion (HPT), equal channel angular pressing (ECAP) [8], friction stir processing (FSP) [9], twist extrusion (TE) [10], and others. Classical extrusion and hydro extrusion methods are also applied, and they have demonstrated effectiveness in the consolidation and grain refinement of Al alloy powder composites [11]. The authors of [11] showed that AA5xxx alloys can be efficiently strengthened up to a flow stress exceeding 450 MPa by both the hydro extrusion of solid preforms and extrusion compaction of nanopowders, and both obtained composites exhibited tensile elongation values greater than 10%.…”

“…Classical extrusion and hydro extrusion methods are also applied, and they have demonstrated effectiveness in the consolidation and grain refinement of Al alloy powder composites [11]. The authors of [11] showed that AA5xxx alloys can be efficiently strengthened up to a flow stress exceeding 450 MPa by both the hydro extrusion of solid preforms and extrusion compaction of nanopowders, and both obtained composites exhibited tensile elongation values greater than 10%. It is important to note the excellent mechanical properties of severely deformed alloys, which are based on grain size reduction and strain hardening.…”

Microstructure Evolution and Texture Development in a Cu-8.5%AT. AL Material Subjected to Hydrostatic Extrusion

“…The extrusion pressure is affected by geometrical factors such as extrusion ratio and die angle, the flow stress of the material, and the friction forces between die and billet [6]. At present, most of the available publications are focused on the effect of SPD on polycrystalline materials [7][8][9][10]. The authors of the present paper were concerned with investigating changes in single crystals and polycrystalline material subjected to SPD realized by HE.…”

Thermo-Mechanical Processing of Rapidly Solidified 5083 Aluminium Alloy - Structure and Mechanical Properties

“…On the contrary, aluminium alloys of 5xxx series are known to be weldable and corrosion resistant, however due to lack of the precipitation strengthening mechanism, poses only moderate strength. It is known that susceptibility of Al-Mg system to precipitation hardening is negligible, thus considering significant improvement of mechanical properties of Al-Mg alloys research interest should be focused on hardening mechanisms based on: solid solution, deformation and grain size strengthening [1].…”