Abstract Here, we report molecular dynamics (MD) calculations of spall strength in pure magnesium and magnesium alloys with 1-8 at.% aluminum in solid solution. The Mg–Al solid solution alloys are found to have a weaker spall strength than pure magnesium, e.g. the spall strength of Mg-8 at.% Al is found to be 12% lower than pure magnesium. Moreover, we find that the spall strength of Mg–Al alloys monotonically decreases with increasing concentration of Al content. We term this phenomena solid solution softening (SSS) of spall strength, which is contrary to the conventional solid solution strengthening observed in most alloys (including Mg–Al alloys) deformed at quasi-static loading rates. We argue that this transition from solid solution strengthening at quasi-static rates to SSS at extreme loading rates is due to a transition from dislocation glide dominated failure at low rates to dislocation nucleation dominated failure at extreme rates. The distortion of the host lattice by solute atoms is found to retard dislocation glide, but aids dislocation nucleation. We thus conclude that SSS may manifest in any dislocation-starved system, regardless of loading rate. To this end, we propose a theoretical model for spall strength in dislocation-starved bulk and nanoporous alloys that exhibits remarkable agreement with our molecular dynamics calculations. Our theory bares some resemblance to the double kink nucleation enhancement theory for low-temperature SSS in some body centered cubic metals, e.g. refractory metals alloyed with group IV-VIII elements.

中文翻译：

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缺乏位错的 Mg-Al 合金中的固溶软化

摘要 在此，我们报告了纯镁和含 1-8 at.% 铝的固溶体镁合金的剥落强度的分子动力学 (MD) 计算。发现 Mg-Al 固溶体合金具有比纯镁更弱的剥落强度，例如发现 Mg-8 at.% Al 的剥落强度比纯镁低 12%。此外，我们发现 Mg-Al 合金的剥落强度随着 Al 含量浓度的增加而单调降低。我们将这种现象称为剥落强度的固溶软化 (SSS)，这与在准静态加载速率下变形的大多数合金（包括 Mg-Al 合金）中观察到的常规固溶强化相反。我们认为，这种从准静态速率下的固溶强化到极端加载速率下的 SSS 转变是由于从低速率下的位错滑动主导失效到极端速率下位错成核主导失效的转变。发现由溶质原子引起的主晶格畸变会延迟位错滑移，但有助于位错成核。因此，我们得出结论，无论加载速率如何，SSS 都可能出现在任何位错饥饿系统中。为此，我们提出了位错缺乏的块状和纳米多孔合金中的剥落强度的理论模型，该模型与我们的分子动力学计算非常一致。我们的理论与某些体心立方金属中低温 SSS 的双扭结成核增强理论有一些相似之处，例如