The influence of the complex deformation on the microstructure and mechanical properties of the model Al-Li alloys

Abstract

The present study demonstrate the effect of the combined deformation (hydrostatic extrusion and rolling) on microstructure and mechanical properties of model AlLi alloys. It has been shown the anisotropy of material structure and properties. Additionally it has been demonstrated increase of yield strength at the result of the plastic deformation. KEYWORDS: Al-Li alloy, hydrostatic extrusion, microstructure and properties W pracy przedstawiono wpływ łączonego odkształcenia wyciskania hydrostatycznego i walcowania na zimno na mikrostrukturę i właściwości modelowych stopów Al-Li. Badania wykazały obecność anizotropii struktury materiału i właściwości. Ponadto przedstawiono wzrost wła-ściwości wytrzymałościowych w wyniku odkształcenia plastycznego. SŁOWA KLUCZOWE: stopy Al-Li, wyciskanie hydrostatyczne, mikrostruktura i właściwości Al-Li alloys are extensively used in many areas of industry, especially the aircraft, because of low density and strong ability to hardening. They are suitable materials for basic investigation, where are interested in the interaction between deformation and microstructure [1÷5]. One of the method of strengthening is plastic deformation or heat treatment. The aim of the present study was analyzed of complex deformation influence on the microstructure and mechanical properties of the model Al-Li alloys. Materials and methodsThe materials used in the investigations were two model aluminum -lithium alloys of a chemical composition (wt. %) given in Tab. I. The second alloy was subjected the additional heat treatment (heat treated at 823 K for 10 h and subsequently water-quenched to room temperature and than aging at 473 K for 2 h -T6 treatment).In the first step the alloys were deformed by hydrostatic extrusion (HE) method in the range of the true strain ε = 2.4. The second step the bars were cold rolled (CR) in accordance with direction of the extrusion process. Finally the samples, as a result of plastic deformation had about 4 mm width and 1 mm of thickness.The structures of the deformed samples was examined on transverse and longitudinal sections to the extrusion direction. Microstructures were examined by light microscopy with polarized light beam (LM) and transmission electron microscope (TEM) at an accelerating voltage of 120 keV. The obtained images (perpendicular and parallel sections) were analyzed quantitatively by the stereological methods using special software for image analysis [6]. The grain sizes were determined for more than 400 randomly selected grains. In order to determine mechanical properties tests such as microhardness measurements (HV 0.2) and compression test were performed. A microhardness measurements were carried out for the samples at perpendicular and parallel sections as well. Presented values are average from 30 measurements each. From the compression test were appointed the yield strength value only. Because of small dimensions of samples yield strength were define by compression test. The obtained results well correspond to the values presented on the work [...

The Effects of Additional Two Bendings on Manufacturing Thin-walled Tube made of AZ31 Magnesium Alloy Fabricated by New Compound Extrusion

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