Hot Deformation Behavior Of N18Zr Alloy With Different Orientation

In this paper, the as received material was annealed Zr alloy plate after hot rollingwith bimodal basal texture. Four cylinder specimens for compression were cut from theplate with compressive axes aligned in normal direction-transverse direction (ND-TD)plane and0°,30°,60°and90°to ND respectively. Uniaxial compression was performedat different temperatures and strain rates. Microstructures and textures of specimensbefore and after compression were characterized with EBSD equipped in SEM. Schmidfactors for different deformation modes were calculated according to the data collectedfrom EBSD. Effects of initial orientation on mechanical behavior, work hardening anddynamical recrystallization behavior were discussed in detail. The relationship betweenmechanical properties and microstructure was study systematically. Main conclusionsdrew from the paper are as following:Initial orientation has remarkable influence on the mechanical behavior of N18Zirconium alloy under high temperature. The macroscopic flow stress and dynamicsoftening declines with the increase of initial angle between compressive axis and NDduring compressive deformation. For0°and30°specimens, prismatic slip much moredifficult to operate compared with other specimens with higher angle. Thus higherexternal stress is required to activate pyramidal <c+a>to coordinate plastic strain. As thecompression strain accumulating, DRX appears, which decrease the density ofdislocation. So the macroscopic flow stress declines after the intiation of DRX. For60°and90°specimens, prismatic slip is easy to operate, meanwhile {1012}tensile twinningis activated at the early stage of the deformation, which make contribution to loweryield stress and flow stress. With the increasing strain, grain size is refined by twinningand grains orientation change to the hard orientation, which weaken the dynamicsoftening at high temperature. However, the mechanical anisotropy is graduallyweakening as temperature increasing.Strain rate has a obvious effect on the initiation of twinning. With the strain rate of5s-1, a lot of {1011}compressive twinning can be examed at strain of10%in0°specimen and at strain of30%in both0°and90°specimens.During the early stage ofhot compression deformation,{1012} tensile twinning and {1011}compressivetwinning are activated in the four kinds of specimens at the strain rate of0.001s-1.Meanwhile,{1012} tensile twinning is more remarkable in the60°and90° specimens.{1011}compressive twinning mainly appear in the0°and30°specimens andthe amount of {1011}compressive twinning is relative less.In all of the four specimens, the c axis of most grains are turned to directionparallel to compressive axis after60%compression and the specimens all show thebimodal basal texture. At high temperature, the higher the initial angle, the weakereffect of the recrystallization is observed, especially in90°specimen. The reason isattributed to he relatively low stored energy caused by tensile twinning and easyprismatic slip. The features of continuous recrystallization is observed after60%deformation.