Hydrogen in Metals

氢在金属中无处不在，它在生产过程中进入，在使用过程中因腐蚀而进入。 氢会导致脆化、硬化和内部损坏。 氢可以降低断裂韧性，并且在某些金属中，氢可以沉淀形成在负载下开裂的脆性金属。 这个过程被称为延迟氢化物开裂（DHC），这是一个特殊的问题，锆合金用于化学和核电站的压力边界。 在压力下破裂的后果可能是高温蒸汽的剧烈释放。 用于容纳核燃料的锆合金的失效可能意味着在反应堆运行期间以及以后乏燃料长期储存时释放放射性。目前，通过对操作条件设置非常保守的限制来确保锆合金的安全操作。 尽管经过了几十年的研究，但关于锆中的氢仍然有很多东西需要了解。 最近，申请人的研究小组报告了锆在冷却时溶解，而在加热时沉淀，这真是奇怪。 我们期望相反的事情发生：当加热时溶解，当冷却时沉淀。 这些观察结果是前所未有的，正在发展的解释也是如此。 这种奇怪的行为只发生在一个很小的温度范围内，但它发生在反应堆和化工厂运行的温度下。 锆的性质如何随着氢的进入而变化的含义开始显示：氢扩散变化，并且在不期望形成氢的温度下发生延迟氢化物开裂。 DHC模型自70年代中期以来一直在发展。 在过去的10年里，这些模型受到了严重的质疑。 申请人的研究小组已经引入了一种新的DHC模型，该模型已成功用于预测广泛的实验结果;这是前所未有的，令人兴奋的，并结合了对基础物理学的更好理解。一个可靠的DHC物理模型将有助于更好地预测锆部件的故障，从而提高化工厂、核反应堆和长期储存的乏核燃料的安全性。 人们对氢和氘在金属中，特别是在锆合金中的行为有了新的认识。 这个提案的目的是与一群有才华的学生一起系统地探索这种新理解的含义，并将其提升到更高的水平。

Hydrogen is ubiquitous in metals, it enters during production and from corrosion during service. Hydrogen causes embrittlement, hardening and internal damage. Hydrogen can reduce fracture toughness and, in some metals, hydrogen can precipitate forming brittle hydrides that crack under load. The process is called Delayed Hydride Cracking (DHC) and it is a particular problem for zirconium alloys that are used in chemical and nuclear plants as pressure boundaries. The consequence of cracking under pressure can be violent release of high temperature steam. Failure of zirconium alloys used to contain nuclear fuel could mean release of radioactivity during reactor operation and later when the spent fuel is in long-term storage. Currently, safe operation with zirconium alloys is ensured by placing very conservative limits on operating conditions. In spite of decades of research there is still much to learn about hydrogen in zirconium. Recently, the applicant's research group has reported hydrides in zirconium dissolving when cooled, and precipitating when heated, which is truly bizarre. We expect the opposite to happen: things dissolve when heated and precipitate when cooled. These observations are unprecedented, and so is the explanation being developed. This bizarre behavior only happens over a small temperature range, but it happens at the temperatures where reactors and chemical plants operate. The implications for how properties of zirconium change with hydrogen ingress are beginning to show: hydrogen diffusion changes, and delayed hydride cracking occurs at temperatures where you do not expect hydrides to form. Models of DHC have been developing since the mid-70s. In the last 10 years these models have been critically questioned. The applicant's research group have introduced a new model for DHC that has successfully been used to predict a broad spectrum of experimental results; this is unprecedented and exciting, and incorporates a better understanding of the underlying physics. A reliable robust physical model of DHC will lead to better predictions of failures of zirconium components and, thus, improved safety for chemical plants, nuclear reactors and spent nuclear fuel in long-term storage. A new understanding is emerging of how hydrogen and hydrides behave in metals, and in zirconium alloys in particular. The goal of this proposal is to have fun with a group of talented students systematically exploring the implications of this new understanding, and taking it to a higher level.