Cyclic deformation and strain burst behavior of Cu-7at.%Al and Cu-16at.%Alsingle crystals with different orientations

[(1) over bar 12] Cu-7at."/DAl single crystals as well as [(1) over bar 23] , [(1) over bar 17] and [023] Cu-16at.%Al single crystals were cyclically d eformed under constant plastic strain control at room temperature. The cycl ic hardening curve of [(1) over bar 12] Cu-7at.%uAl single crystal can be d ivided into three stages, namely initial non-hardening stage, rapid hardeni ng stage and saturation stage. The cyclic stress-strain (CSS) curve exhibit ed a plateau region in the range of gamma (pl). from 1.1 x 10(-3) to 4.5 x 10(-3). The saturation stress of the plateau is about 27 MPa. The occurrenc e of strain burst depends on the applied plastic strain amplitude gamma (pl ). No strain burst was detected when gamma (pl), was below 4.4 x 10(-4) or above 1.1 x 10(-3). The cyclic deformation and strain burst behavior of [(1 ) over bar 23], [(1) over bar 17] and [023] Cu-16at.%Al single crystals are different from that of [(1) over bar 12] Cu-7at.%Al single crystal. The cy clic deformation of all three differently oriented Cu-16%Al single crystals is unstable with the frequent occurrence of irregular strain bursts. The s pecimens cyclically hardened at a very low rate and saturation was not atta ined at high strain amplitudes. The experimental results indicate that the crystallographic orientation has almost no effect on the cyclic deformation and strain burst behavior of Cu-16at.%Al single crystals. The evolution of slip bands during cyclic deformation in both Cu-7at.%Al and Cu-16at.%Al si ngle crystals is similar to the development of Luders band. The percolation of slip bands along the gauge length is generally accompanied by strain bu rsts. The above experimental results were explained in terms of the variati on of slip mode with Al content in the alloys and the corresponding strain localization during cycling. (C) 2001 Elsevier Science B.V. All rights rese rved.