Features of dynamic fracture of ultrafine-grained aluminum alloy AMg4.5

Abstract

The features of the fracture of the aluminum alloy AMg4.5 under dynamic tension according to the Kolsky methods using Split-Hopkinson pressure bar are considered. Experimental and theoretical data of strength characteristics of the alloy in the initial coarse-grained and ultrafine-grained states are presented. It is shown that the high degree of deformation of the material obtained in the process of severe plastic deformation by torsion under high pressure has a negative effect on the dynamic strength of the material. Keywords: dynamic strength, incubation time criterion, Split-Hopkinson pressure bar, severe plastic deformation.

Effect of annealing and additional deformation on the dynamic properties of ultrafine-grained AMg4.5 alloy

“…The offset yield strength increased from 120 to 725 MPa, the ultimate elongation decreased from 11% to values close to 0%. The high strength of the material and the inability to plastically deform led to decrease in the material strength with increase in the rate of stress growth [3]. In order to increase the material plasticity, a set of heat-strain treatments of the material in the UFG state was carried out.…”

“…Dynamic tension experiments were carried out according to the Kolsky method using split Hopkinson rods [18,19] on samples similar to those used under quasi-static loading conditions, with a work part 5 mm long and 2 mm wide. The unit consists of a pneumatic loading device with a caliber with the gage of 30 mm, striker 400 mm long, split Hopkinson pressure bars with the diameter of 20 mm and loading bar length of 3000 mm, as well as a measuring bar -1500 mm [3]. The striker is accelerated by compressed air supplied by the compressor into the chamber, pressure is monitored by a pressure gage.…”

“…At the same time, the strength characteristics increasing of alloys of Al−Mg system by standard methods is limited. Example of the AMg4.5 alloy [3] shows the possibility of increasing the material strength in the static loading range by three using the methods of severe plastic deformation (SPD) was shown [4][5][6][7][8][9][10]. In dynamic tension experiments the aluminum alloy in the ultra-fine grain (UFG) state was destroyed at stresses lower than its static strength.…”