论文标题
部分可观测时空混沌系统的无模型预测
Dynamic Hardness Evolution in Metals from Impact Induced Gradient Dislocation Density
论文作者
论文摘要
对金属的动态行为的清晰了解对于开发出色的结构材料以及改善材料加工技术（例如冷喷雾和射击）至关重要。使用高速度（从120 m/s到700 m/s；应变速率> 10^7 1/s）微预测撞击测试和准危率（应变速率：10^-2 1/s）纳米识别，我们研究了与（001）（001）（001），（011），（1111）和（11111），（1111），（1111），（1111）的应变率依赖性机械机械行为。在所有三个晶体方向上，动态硬度最初随着冲击速度的增加而增加，并以硬度的高度达到高原性5倍，高5倍。基于恢复原状和验尸后的kikuchi衍射分析，我们表明具有梯度位错密度演化的不同塑性变形机制决定了动态行为。我们还发现了一种独特的变形型塑料状态 - 超越深层塑料状态，具有独特的应变速率不敏感的微结构演化和动态硬度。我们的工作还展示了一种有效的方法，可以通过高速弹丸影响在金属中引入强烈的空间梯度以增强表面机械性能，因为它可以用于材料处理技术（例如射击和表面机械损耗处理）中。
A clear understanding of the dynamic behavior of metals is critical for developing superior structural materials as well as for improving material processing techniques such as cold spray and shot peening. Using a high velocity (from 120 m/s to 700 m/s; strain rates >10^7 1/s) micro-projectile impact testing and quasistatic (strain rates: 10^-2 1/s) nanoindentation, we investigate the strain-rate-dependent mechanical behavior of single-crystal aluminum substrates with (001), (011), and (111) crystal orientations. For all three crystal orientations, the dynamic hardness initially increases with increasing impact velocity and reaches a plateau regime at hardness 5 times higher than that of at quasistatic indentations. Based on coefficient of restitution and post mortem transmission Kikuchi diffraction analyses, we show that distinct plastic deformation mechanisms with a gradient dislocation density evolution govern the dynamic behavior. We also discover a distinct deformation regime-stable plastic regime-that emerge beyond the deeply plastic regime with unique strain rate insensitive microstructure evolution and dynamic hardness. Our work additionally demonstrates an effective approach to introduce strong spatial gradient in dislocation density in metals by high-velocity projectile impacts to enhance surface mechanical properties, as it can be employed in material processing techniques such as shot peening and surface mechanical attrition treatment.
