Coherent precipitation of cuboidal B2/L2₁ nanoparticles in body-centered-cubic (BCC) based high entropy alloys (HEAs) is crucial for the improvement of mechanical properties. The present work investigated the influence of Ti addition on the phase constitutions and particle morphology in (Al,Ti)_0.7M₅ HEAs (M = Ni₁Co₁Fe_1.5Cr_1.5 and Ni₁Co₁Fe₁Cr₂) with different Al/Ti ratios. Series of alloy rods were prepared by suction-cast processing, and their microstructures and mechanical properties were then characterized comprehensively. It was found that the substitution of Ti for Al can change the phase structures of ordered precipitates, from B2-NiAl to L2₁-Ni₂AlTi. Furthermore, the particle morphology of L2₁/B2 precipitates is closely related to the lattice misfit ε between L2₁/B2 phase and BCC matrix, in which a moderate ε (ε = 0.4–0.5%) can contribute to the formation of cuboidal L2₁/B2 precipitates in BCC matrix, while a large ε (ε > 1.0%) will cause a lath-like microstructure. High compressive yield strengths (above 1500 MPa) of these Al/Ti-contained HEAs with cuboidal coherent microstructure are primarily attributed to the particle size in light of the precipitation strengthening mechanism. In addition, the excess addition of Ti will transform the matrix structure of alloys from the BCC to the σ phase, leading to a serious brittleness.

基于体心立方（BCC）的高熵合金（HEA）中长方体B2 / L2 ₁纳米粒子的相干沉淀对于改善机械性能至关重要。本工作研究了Ti添加对（Al，Ti）_0.7 M ₅ HEAs（M = Ni ₁ Co ₁ Fe _1.5 Cr _1.5和Ni ₁ Co ₁ Fe ₁ Cr _2中的相组成和颗粒形态的影响）具有不同的Al / Ti比。通过抽铸工艺制备了一系列合金棒，然后对它们的微观组织和力学性能进行了全面表征。发现用Ti代替Al可以改变有序析出物的相结构，从B2-NiAl到L2 ₁ -Ni ₂ AlTi。此外，L2 ₁ / B2沉淀物的颗粒形态与L2 ₁ / B2相与BCC基质之间的晶格失配ε密切相关，其中适度的ε（ε  = 0.4-0.5％）有助于长方体L2的形成₁ / B2在BCC基质中沉淀，而较大的ε（ε > 1.0％）将导致板条状的微观结构。这些具有立方体相干微观结构的含Al / Ti的HEA的高抗压屈服强度（高于1500 MPa）主要是根据沉淀增强机理来归因于颗粒尺寸。此外，过量添加Ti会使合金的基体结构从BCC转变为σ相，从而导致严重的脆性。