713 Russian Physics Journal, Vol. 54, No. 6, November, 2011 (Russian Original No. 6, June, 2011) DEFORMATION BEHAVIOR AND SPALLING FRACTURE OF A HETEROPHASE ALUMINUM ALLOY WITH ULTRAFINE- GRAINED AND COARSE-GRAINED STRUCTURE SUBJECTED TO A NANOSECOND RELATIVISTIC HIGH-CURRENT ELECTRON BEAM E. F. Dudarev, 1 O. A. Kashin, 2 A. B. Markov, 3 A. E. Mayer, 4 UDC 538.591 – 405:620.118 A. N. Tabachenko, 1 N. V. Girsova, 2 G. P. Bakach, 1 S. A. Kitsanov, 3 M. F. Zhorovkov, 1 A. B. Skosyrskii, 1 and G. P. Pochivalova 1 The results of a comprehensive experimental-theoretical investigation of the deformation behavior, regular features and mechanism of spalling fracture in an Al–Mg–Li–Zr heterophase aluminum alloy with ultrafine- and coarse-grained structure subjected to a nanosecond high-current electron beam with the power density 7·10 9 W/cm 2 are presented. The patterns of formation and propagation of a shock wave are discussed, and so is the behavior of the respective reflected wave, once the former is reflected from the back surface. Common regularities of variation in the thickness of the spalled layer and its plastic deformation degree are observed in the cases of ultrafine- and coarse-grained structure. It is shown that spalling resistance of the Al–Mg–Li–Zr heterophase alloy is controlled by the ultrafine-grained structure formed in the spalling zone under the tensile wave rather than by the initial grain structure. Keywords: heterophase alloy, ultra-fine-grained structure, electron beam, shock wave, spalling fracture. INTRODUCTION Formation of ultra-fine-grained (submicro- and nanocrystalline) structure in metals and alloys using the methods of severe plastic deformation improves their strength while maintaining acceptable plasticity [1–7]. These data were obtained at the strain rates less than 1·10 –1 s –1 in the region of moderate homological temperatures. Only more recent publications report deformation behavior and fracture of ultra-fine-grained metallic materials at the strain rates 10 4 –10 6 s –1 [8–12]. It should be noted that along with the high-speed impact of plates the authors of these studies used shock waves generated by the exposure to high-current electron beams. It turned out that high-speed deformation of some of the metallic materials results in a higher yield strength in the case of their ultra-fine-grained structure than in coarse-grained, while in the other metallic materials it is vice versa. In particular, the yield strength of armco-iron both under the dynamic and quasi-static loading is higher for its ultra-fine-grained than coarse-grained structure. On the other hand, yield strength of titanium and heterophase Al–Mg–Li–Zr alloy is lower in ultra-fine-grained states than in the case of their coarse-grained structure. According to [10], this is due to much weaker rate dependence of the yield strength during transition from coarse-grained to ultra-fine-grained structure. The authors of [10], however, did not discuss the structural factors governing the variation in this rate dependence of the yield strength. In [11, 12], common features and peculiar deformation behavior and spalling fracture of ultra-fine- and coarse- grained FCC-metals (aluminum, copper) subjected to high-speed deformation by nanosecond relativistic electron beams 1 V. D. Kuznetsov Siberian Physical-Technical Institute of Tomsk State University, Tomsk, Russia, 2 Institute of Strength Physics and Materials Science of the Siberian Branch of the Russian Academy of Sciences, Tomsk, Russia, 4 Chelyabinsk State University, Chelyabinsk, Russia, e-mail: dudarev@spti.tsu.ru. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 89–95, June, 2011. Original article submitted February 25, 2011. 1064-8887/11/5405-0713 ©2011 Springer Science+Business Media, Inc.