探究新型磁性Heusler合金对于开发新一代智能传感材料具有重要的意义。本工作采用第一性原理计算对8种新型A₂BTi型磁性功能合金，包括3种钴基合金(Co₂MnTi、Co₂FeTi和Co₂NiTi)、3种铁基合金(Fe₂MnTi、Fe₂CoTi和Fe₂NiTi)以及2种镍基合金(Ni₂FeTi、Ni₂CoTi)，在四方晶格畸变过程中的相稳定性演化进行了理论计算，并对其L2₁相稳定性演变规律及背后机制进行了探讨。研究发现，价电子浓度和磁性是决定A₂BTi型合金L2₁相结构稳定性的关键参数。针对理论计算筛选出的L2₁相为非最稳定结构的Co₂NiTi、Fe₂NiTi和Ni₂CoTi，分别制备了合金样品并对其晶体结构、相变行为、磁性能、电阻和力学性能进行了实验研究。结果表明，室温下Co₂NiTi由有序面心立方L1₂结构基体相和六方Co₃Ti型第二相构成，Fe₂NiTi由六方Fe₂Ti型基体相和四方FeNi型第二相构成，Ni₂CoTi为单一的Ni₃Ti型六方结构。Co₂NiTi、Fe₂NiTi和Ni₂CoTi均不存在一阶结构相变，这可能与其L2₁结构低的晶格稳定性致使其难以被形成有关。Fe₂NiTi和Ni₂CoTi具有较强的磁性且存在二阶Curie磁性转变。Fe₂NiTi具有高的压缩强度(1280 MPa)、中等压缩应变(5%)及较大电阻(120 μΩ·cm)，而Co₂NiTi和Ni₂CoTi具有优异的压缩塑性和较小的电阻，这3种合金不同的功能行为可能与其价电子浓度差异带来的化学键中金属键和共价键组分比例不同有关。

Exploring novel magnetic Heusler alloys is of great significance for the development of a new generation of smart sensing materials. The A₂BC type magnetic alloy, which comprises transition magnetic metal elements A and B and III-V main group element C (p-block element), has gained significant attention due to its various physical and chemical properties, including semimetallic magnetism, ferromagnetic shape memory effect, multicaloric effect, and superconductive effect. In this study, eight new A₂BTi type magnetic functional alloys, including three Co-based alloys (Co₂MnTi, Co₂FeTi, and Co₂NiTi), three Fe-based alloys (Fe₂MnTi, Fe₂CoTi, and Fe₂NiTi), and two Ni-based alloys (Ni₂FeTi and Ni₂CoTi), were investigated for their phase stability against tetragonal distortion using first-principles calculation. The underlying mechanism for the stability of the L2₁ phase was discussed. The results show that valence electron concentration and magnetism are the key parameters in determining the structural stability of L2₁ phase in A₂BTi type alloys. Co₂NiTi, Fe₂NiTi, and Ni₂CoTi alloy samples, whose L2₁ structure is an unstable phase, were prepared, and their crystal structure, phase transformation, magnetic properties, electrical resistance, and mechanical properties were investigated experimentally. The results show that at 298 K, Co₂NiTi is composed of an ordered face-centered cubic L1₂ structured matrix phase and a hexagonal Co₃Ti-type second phase, Fe₂NiTi is composed of a hexagonal Fe₂Ti-type matrix phase and a tetragonal FeNi-type second phase, and Ni₂CoTi has a single hexagonal Ni₃Ti-type structure. The fact that no compound undergoes a first-order structural phase transition may be due to the weak stabilities of their L2₁ phases. Fe₂NiTi and Ni₂CoTi have strong magnetic properties and undergo a second-order Curie magnetic transition during cooling. Fe₂NiTi has high compressive strength (1280 MPa), moderate compressive strain (5%), and large resistance (120 μΩ·cm), while Co₂NiTi and Ni₂CoTi have excellent compressive plasticity and small resistance. This phenomenon may be related to the different proportions of metallic and covalent bonding caused by the difference in valence electron concentration of the three alloys.