Martensitic transformation can easily induce a maximum hardness value of 800–900 HV (Vickers hardness) for steels with carbon contents of 0.6 wt.% and above. However, the occurrence of martensitic transformation in pure iron requires exceptionally high cooling rates (10⁵–10⁶°C/s), and the maximum achievable hardness is only about 150 HV. Here we report an extreme hardness of 830 HV in pure iron obtained through high pressure induced martensitic transformation at a rather slow cooling rate of just 10°C/s. This unprecedented strength originates from the formation of twin-related martensitic laths with an average thickness of 3.8 nm.

中文翻译：

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高压诱导的纳米孪晶马氏体在纯铁中具有前所未有的强度

对于碳含量为0.6 wt。％及以上的钢，马氏体相变很容易引起800-900 HV（维氏硬度）的最大硬度值。但是，纯铁中发生马氏体相变需要极高的冷却速度（10 ⁵ –10 ⁶ °C / s），并且最大可达到的硬度仅为150 HV。在这里，我们报道了通过高压诱导的马氏体相变以10°C / s的相当慢的冷却速度获得的纯铁中的830 HV的极高硬度。这种前所未有的强度源自平均厚度为3.8 nm的双相马氏体板条的形成。