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Abstract：
The response of metals and their microstructures under extreme dynamic conditions can be markedly different from that under quasistatic conditions. Traditionally, high strain rates and shock stresses are achieved using cumbersome and expensive methods such as the Kolsky bar or large spall experiments. These methods are low throughput and do not facilitate high-fidelity microstructure-property linkages. In this work, we combine two powerful small-scale testing methods, custom nanoindentation, and laser-driven microflyer (LDMF) shock, to measure the dynamic and spall strength of metals. The nanoindentation system is configured to test samples from quasistatic to dynamic strain-rate regimes. The LDMF shock system can test samples through impact loading, triggering spall failure. The model material used for testing is magnesium alloys, which are lightweight, possess high-specific strengths, and have historically been challenging to design and strengthen due to their mechanical anisotropy. We adopt two distinct microstructures, solutionized (no precipitates) and peak-aged (with precipitates) to demonstrate interesting upticks in strain-rate sensitivity and evolution of dynamic strength. At high shock-loading rates, we unravel an interesting paradigm where the spall strength vs. strain rate of these materials converges, but the failure mechanisms are markedly different. Peak aging, considered to be a standard method to strengthen metallic alloys, causes catastrophic failure, faring much worse than solutionized alloys. Our high-throughput testing framework not only quantifies strength but also teases out unexplored failure mechanisms at extreme strain rates, providing valuable insights for the rapid design and improvement of materials for extreme environments.
摘要：
在极端动态条件下，金属及其微观结构的响应可能与在准静态条件下的响应明显不同。传统上,高应变率和冲击应力是使用繁琐和昂贵的方法，如Kolsky酒吧或大型spall实验。这些方法的产量低,并且不有利于高保真的微结构-性能连接。在这项工作中,我们结合了两种强大的小规模测试方法，自定义纳米压痕，和激光驱动的微飞片（LDMF）冲击，测量金属的动态和剥落强度。纳米压痕系统被配置为测试从准静态到动态应变速率状态的样品。LDMF冲击系统可以通过冲击载荷测试样品，触发spall失败。用于测试的模型材料是镁合金，重量轻，具有高特异性优势，并且由于其机械各向异性，历来具有设计和加强的挑战性。我们采用两种不同的微观结构，固溶（无沉淀物）和峰值老化（有沉淀物），以证明应变率敏感性和动态强度演变方面的有趣上升。在高冲击载荷率下，我们解开了一个有趣的范例，其中spall力量与这些材料的应变率收敛，但是失败机制明显不同。峰值老化,被认为是强化金属合金的标准方法，导致灾难性的故障，比固溶合金差得多。我们的高通量测试框架不仅量化了强度，还梳理了极端应变率下未开发的失效机制，为极端环境材料的快速设计和改进提供有价值的见解。
