铝/钛比对钛铝基轻质高熵合金相稳定性和力学性能的影响

Effect of Al/Ti Ratio on Phase Stability and Mechanical Properties of Ti-Al-Based Lightweight High-Entropy Alloys

摘要:

轻质高熵合金是用于先进结构应用的一类极具前景的材料。然而，要精确控制其相形成过程和力学性能仍是一项重大挑战。尽管常规的经验参数（混合焓ΔH_mix、价电子浓度、原子尺寸差异δ、电负性差值Φ）为Ti-Al基轻质高熵合金的相稳定性提供了通用指导，但它们的预测准确性是有限的。Al/Ti原子比（γ，即铝/钛比）是精确控制微观结构的关键准则。基于此参数，设计并合成了一系列Ti_(50–x)Al_(6.5+x)V_11.5Nb_14.5Zr_17.5合金。结果表明：γ严格控制着B2相的析出、短程有序程度以及晶粒细化。此外，当γ值约为2.0（Ti₄₆Al_10.5合金）时，能实现高屈服强度（>1 GPa）和高拉伸延展性（>20%）的最佳协同效应，而γ值过高则会导致脆化。本研究确立γ为关键组成参数，并通过综合参数控制和元素比例控制为设计高性能轻质高熵合金提供了一个实用框架。

Abstract:

Lightweight high-entropy alloys (LWHEAs) represent a promising class of materials for advanced structural applications. However, achieving precise control over their phase formation and mechanical properties remains a significant challenge. Although the conventional empirical parameters (mixing enthalpy ΔH_mix, valence electron concentration, atomic size mismatch δ, and electronegativity difference Φ) provide general guidance for phase stability in Ti-Al-based LWHEAs, their predictive accuracy is restricted. The Al/Ti atomic ratio (γ, namely Al/Ti ratio) is a more decisive and precise criterion for microstructure control. Guided by this parameter, a series of Ti_(50–x)Al_(6.5+x)V_11.5Nb_14.5Zr_17.5 alloys were designed and synthesized. Results reveal that γ critically governs the precipitation, extent of short-range ordering, and grain refinement of B2 phase. Additionally, a moderate γ value of approximately 2.0 (Ti₄₆Al_10.5 alloy) yields an optimal synergy of high yield strength (>1 GPa) and considerable tensile ductility (>20%), whereas excessively high γ leads to embrittlement. This work considers γ as a key compositional parameter and provides a practical framework for designing high-performance LWHEAs through integrated parametric and element-ratio control.