In order to verify influence of particle velocity non-uniformity on dynamic recrystallization (DRX), shock tests of D16 Al alloy were conducted under uniaxial strain conditions within strain-rate range of 105÷ 107s-1. The particle velocity non-uniformity arises due to both initial heterogeneity and non-linearity of shock-wave process. Apart from the nature of DRX mechanism, migrational or rotational, the particle velocity non-uniformity facilitates growth of local strain, strain rate and temperature. To adjust a duration of the particle velocity non-uniformity degree, two limiting situations is provided by means of single and double shock loading (reloading). The experimental technique used allows to register both mean particle velocity profile and particle velocity variation which is the quantitative characteristic of velocity non-uniformity. Shock tests of D16 Al alloy in single and reloading regimes [ show that dynamic recrystallization takes place only in the second case. The reloading regime initiates a ten-fold increase in duration of the particle velocity non-uniformity stage, which is sufficient for fulfillment of the well-known DRX conditions:γ3,dγ/dt104s1,T0.4Tm. The regions of DRX with equal-axis grains of ~1 μm in diameter are revealed with the metallography and X-ray analysis.
Two regimes, equilibrium and non-equilibrium interaction of shock wave and inner structure of solid are studied. The theoretical analysis of the regimes is carried out by using the concept of the meso-macro momentum exchange. As a test material for the experiments, D16 Al alloy is taken, firstly because of its initial heterogeneity in equilibrium regime of dynamic straining and, secondly, due to increasing heterogeneity in non-equilibrium regime. Shock tests of D16 Al alloy within impact velocity range of 85÷450m/sevidence that maximum dynamic strength is realized under conditions: (i) equilibrium regime of meso-macro momentum exchange, (ii) velocity defect equals to mean velocity variation. In non-equilibrium regime, the shock-induced dynamic recrystallization occurs, which is investigated with the metallography and X-ray analysis.
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