Journal of Alloys and Compounds 382 (2004) 305–310 Structure and properties of dynamically compressed Al99.5 and AlCuZr alloy Maria Richert ∗ , Beata Leszczy ´ nska Department of Structure and Mechanics of Solids, AGH, University of Science and Technology, Al. Mickiewicza 30, 30-059 Cracow, Poland Received 15 September 2003; received in revised form 19 February 2004; accepted 29 February 2004 Abstract The dynamically compressed AlCuZr alloy and technically pure aluminium Al99.5 have been investigated. A jump of microhardness has been found in both materials deformed in the compression test, by a special hammer. In the case of AlCu4Zr alloy it appeared at the true strain of about 0.45 and in the case of Al99.5 at the true strain of about 0.3. The observation performed by optical microscope revealed banded microstructure in Al99.5 and AlCu4Zr from the beginning of deformation. With the increase of deformation the density of bands considerably increased. Any substantial differences between the samples before and after the jump of microhardness were not found. However, thin foil observations showed changes of microstructure above the microhardness transient. The mutually crossing microbands were found in contrast to samples below the transient of microhardness, in which only one family of microbands mostly was observed. © 2004 Elsevier B.V. All rights reserved. Keywords: Band microstructure; Compression; High strain rate 1. Introduction The condition of the material and the deformation param- eters (volume of deformation, deformation rate, change of the deformation path) are the factors significantly affecting the properties and the structure after the deformation pro- cess [1–7]. One of the essential factors is the deformation rate. A characteristic phenomenon in samples deformed dy- namically, in comparison with samples deformed statically, is the occurrence of a greater tendency to strain localization in shear bands [1–5]. Another phenomenon, occurring dur- ing deformation with large strains exerted dynamically, is the local increase of temperature inside these bands [4–7]. In some cases it leads to local occurrence of dynamic recrystal- lization [5]. Shear bands forming at high deformation rates and high deformation values are defined as adiabatic shear bands [6,7]. They are characterized by a specific structure resulting from the occurrence of local deformation softening in the area of the bands. In the area of the bands, the level of the produced heat exceeds the degree of its dissipation to the surrounding material. The maximum temperature, at- ∗ Corresponding author. Tel.: +48-12-617-33-56; fax: +48-12-632-56-15. E-mail address: mrichert@agh.edu.pl (M. Richert). tained locally as a result of this phenomenon, could be of the order of some hundreds degrees, above the temperature of the surrounding material [8]. This paper is concentrated on the investigations of the development of the banded struc- ture, formed in the dynamically compressed aluminium and AlCu4Zr alloy. 2. Investigation method Cylindrical samples 6–10 mm high, from Al99.5 (indus- trial pure aluminium) and AlCu4Zr0.5 alloy were com- pressed on a falling-weight-type impact testing machine (Fig. 1) at the strain rate ε = 2.9 × 10 2 s -1 in the range of true strains ε = 0.2–0.6 for Al99.5 and ε = 0.2–0.5 for AlCu4Zr0.5. The samples were placed into the distance ring of different height, h. The height of the distance ring deter- mined the value of deformation exerted on the samples. The small initial height of the samples (6–10 mm) in comparison with the path of the beater (1000 mm), allowed the assump- tion that the strain rate, during the compression test, could be taken as the average value. The calculations for AlCu4Zr alloy indicated that the value of strain rate at the lowest deformation was ε = 1.8 × 10 2 s -1 , and ε = 4 ×10 2 s -1 at the highest degree of compression. For aluminium these 0925-8388/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.jallcom.2004.06.004