新型Ni-Mn-Ti全d族Heusler合金表现出优异的弹热效应和力学性能，在功能材料领域具有广阔的应用前景，但由于其奥氏体母相和马氏体相均呈现弱磁性而丧失了传统Ni-Mn基合金的显著磁热效应。本工作通过第一性原理计算研究了Co、Si共掺杂调控Ni-Mn-Ti合金的马氏体相变、磁性能和力学性能。结果表明，掺杂的Si原子倾向于占据Mn亚晶格格点，Co和Si原子在合金中表现出聚集趋势。Co含量的增加导致奥氏体从反铁磁状态转变为铁磁状态，而马氏体则保持反铁磁状态，使其在特定成分下观察到磁-结构耦合转变，这对实现显著的磁热效应至关重要。Si原子掺杂可显著提高合金的强度，同时降低其韧性；Co、Si共掺杂Ni-Mn-Ti合金相比于三元合金在整体上表现出较高的强度。最后，探讨了合金的电子态密度(DOS)以阐明实验中观察到的马氏体相变和磁性能改变的物理机制。

The novel all-d-metal Ni-Mn-Ti Heusler alloys have various application prospects in the field of functional materials owing to their excellent elastocaloric effect and mechanical properties. However, the noteworthy magnetocaloric effect in conventional Ni-Mn-based Heusler alloys is not reflected in Ni-Mn-Ti alloys because of the weak magnetism of both its austenitic parent and martensitic phases. To overcome this limitation, this study explored the effect of Co and Si codoping on the martensitic transformation and magnetic and mechanical properties of Ni-Mn-Ti alloys based on first-principles calculation. The codoping of Co and Si effectively modulated the comprehensive properties of the Ni-Mn-Ti alloys. Specifically, Si atoms tended to directly occupy the Mn sublattice, whereas Co atoms tended to directly occupy the Ni sublattice. Further, the codoped Co and Si atoms exhibited a tendency of aggregated distribution in the alloy. In the Ni-(Co)-Mn-(Si)-Ti alloy, the austenite transformed from an antiferromagnetic state to a ferromagnetic state with increasing Co content. In contrast, the martensite remained in an antiferromagnetic state. This resulted in the observation of a magneto-structural transition at specific compositions, which facilitated the realization of a significant magnetocaloric effect. Furthermore, the Si-doped Ni-Mn-Ti alloy significantly increased its strength while decreasing its toughness. Whereas, the Co and Si-codoped Ni-Mn-Ti alloy exhibited better overall mechanical properties than the ternary. Finally, the study also explored the density of electronic states (DOS) of the alloys to elucidate the physical mechanisms underlying the experimentally observed martensitic transformation and the changes in the magnetic properties.