[论文解读] Chemical inhomogeneities in high-entropy alloys help mitigate the strength-ductility trade-off

E. Ma, Chang Liu|arXiv (Cornell University)|Feb 12, 2024

High Entropy Alloys Studies被引用 9

一句话总结

论文认为高熵合金中的纳米尺度化学非均匀性和局部化学序有助于形成动态位错环境，增强应变硬化并推迟塑性失稳，从而在具有延展性的同时实现高强度。

ABSTRACT

Metallurgists have long been accustomed to a trade-off between yield strength and tensile ductility. Extending previously known strain-hardening mechanisms, the emerging multi-principal-element alloys (MPEAs) offer additional help in promoting the strength-ductility synergy, towards gigapascal yield strength simultaneously with pure-metal-like tensile ductility. The highly concentrated chemical make-up in these 'high-entropy' alloys (HEAs) adds, at ultrafine spatial scale from sub-nanometer to tens of nanometers, inherent chemical inhomogeneities in local composition and local chemical order (LCO). These institute a 'nano-cocktail' environment that exerts extra dragging forces, rendering a much wavier motion of dislocation lines (in stick-slip mode) different from dilute solutions. The variable fault energy landscape also makes the dislocation movement sluggish, increasing their chances to hit one another and react to increase entanglement. The accumulation of dislocations (plus faults) dynamically stores obstacles against ensuing dislocation motion to sustain an adequate strain-hardening rate at high flow stresses, delaying plastic instability to enable large (uniform) elongation. The successes summarized advocate MPEAs as an effective recipe towards ultrahigh strength at little expense of tensile ductility. The insight gained also answers the question as to what new mechanical behavior the HEAs have to offer, beyond what has been well documented for traditional metals and solid solutions.

研究动机与目标

• 激励研究高熵合金（HEAs）中的强度-延展性权衡。
• 解释超细化的化学非均匀性和局部化学序如何影响位错动力学。
• 描述纳米尺度的"nano-cocktail"环境影响屈服与硬化的机制。
• 提出HEAs可以在具有可比纯金属的延展性的同时实现吉帕斯卡级别的强度。
• 强调为设计具备优异机械性能的多主元合金（MPEAs）所具备的更广泛意义。

提出的方法

• 概述高熵合金中化学非均匀性和局部化学序的产生原因。
• 描述纳米尺度化学景观对位错粘滑运动和拖曳力的影响。
• 解释可变的断层能量景观如何减慢位错运动并促进纠缠。
• 论证累积的位错和断层在高应力下维持应变硬化。
• 将这些机制与MPEAs中观察到的强度-延展性协同提升联系起来。

实验结果

研究问题

• RQ1 纳米尺度化学非均匀性和局部化学序在HEAs中如何影响位错动力学？
• RQ2 由此产生的塑性机制能否将应变硬化扩展以缓解MPEAs中的强度-延展性权衡？
• RQ3 可变的断层能量景观和位错相互作用在实现HEAs的高强度与延展性方面的作用是什么？

主要发现

• 化学非均匀性创造出纳米级“nano-cocktail”环境，拖拽位错，使其运动从简单滑翔变为更具阻力的波状路径。
• 可变的断层能量景观减慢位错运动，增加位错相互作用与纠缠的可能性。
• 累积的位错和断层充当动态储存的障碍，在高应力下维持应变硬化。
• 这些机制使多主元合金（MPEAs）实现显著的均匀延伸和改进的强度-延展性协同。
• 该研究将HEAs定位为实现超高强度且与传统金属相比延展性损失最小的一种途径。