Rapid Solidification of High Entropy Alloys

高熵合金（HEA’s）是一类令人兴奋的新型金属材料，通常由5种或5种以上的组成元素以大约等量的形式组合而成。它们代表了传统合金冶金的范式转变，在传统合金冶金中，对单一的、占主导地位的基本元素进行少量添加，通常是为了改善合金的一种或多种性能。值得注意的是，尽管这些HEA的化学成分很复杂，但它们的结构非常简单，通常只包含一个或最多两个简单的结晶相。这再次与传统合金形成对比，传统合金可能包含数十种理想的和虚假的金属间相，通常具有复杂的晶体结构。高熵合金具有许多显著的力学性能，包括在高温下保持高屈服强度。因此，提出了多种应用。在本研究中，我们将研究一系列HEA，研究相组成、微观结构和机械性能作为成分和冷却速率的函数，通过滴管实验获得500- 80000 K s-1的冷却速率。一系列的分析技术将用于表征所得到的材料，包括扫描电镜，透射电镜，x射线衍射和机械测试。

High entropy alloys (HEA's) are an exciting new class of metallic materials in which typically 5 or more constituent elements are combined in approximately equal quantities. They represent a paradigm shift from conventional alloy metallurgy, in which small additions are made to a single, dominant, base element, usually with the intention of improving one or more of the alloys properties. Remarkably, despite their chemical complexity, such HEA's are structurally very simple, generally containing just one, or at most two, simple crystalline phases. This is again in contrast to conventional alloys which may contain dozens of both desired and spurious intermetallic phases, often with complex crystal structures. High entropy alloys possess a number of remarkable mechanical properties, including the retention of high yield strengths at elevated temperature. Consequently, multiple applications have been proposed. In this research we will look at a range of HEA's, studying the phase composition, microstructure and mechanical properties as a function of both composition and cooling rate, with drop-tube experiments giving access to cooling rates in the range 500-80,000 K s-1. A range of analytical technique will be used to characterise the resulting materials, including SEM, TEM, X-ray diffraction and mechanical testing.