Screw vs. edge dislocation strengthening in body-centered-cubic high entropy alloys and implications for guided alloy design

Body-centered-cubic (BCC) high entropy alloys (HEAs) can show exceptionally high strength up to high temperatures. Mechanistic theories are needed to guide alloy discovery within the immense multicomponent HEA compositional space. Here, two new theories for strengthening as controlled by screw and edge dislocations, respectively, are applied to predict the yield stresses of a range of BCC alloys over a wide range of temperatures. Results show that the screw theory, with one fitting parameter, can capture experiments in many dilute and non-dilute alloys while the parameter-free edge theory agrees with experiments in non-dilute alloys having a sufficiently large misfit parameter. These results indicate a transition in single-phase alloy strengthening from traditional screw dominance to edge dominance with increasing misfit that is enabled in complex non-dilute alloys. These results point to the use of the edge theory to guide design of high-temperature alloys in the non-dilute range.

体心立方（Body-centered-cubic, BCC）高熵合金（high entropy alloys, HEAs）在高温环境下仍可展现出优异的高强度性能。在规模庞大的多组分高熵合金成分空间中，亟需通过机制理论指导合金的研发与设计。本文分别采用由螺型位错与刃型位错调控强化的两种新理论，对一系列体心立方合金在宽温度区间内的屈服应力进行预测。研究结果显示，仅需单个拟合参数的螺型位错强化理论，可准确复现多种稀合金与非稀合金的实验数据；而无需拟合参数的刃型位错强化理论，则与失配参数足够大的非稀合金的实验结果相符。上述结果揭示，随着失配参数升高，单相合金的强化机制会从传统的螺型位错主导模式转变为刃型位错主导模式，这一转变可在复杂非稀合金中实现。本研究结果表明，可借助刃型位错强化理论指导非稀合金成分区间高温合金的设计开发。