作为一种重要的核材料，铀材在能源和武器制造方面都是重要的国家战略物资。因为铀材料的放射性以及严格的管控，铀材料的实验研究是十分困难的，关于铀材料的实验数据也十分稀缺。因此，计算模拟是研究铀及铀合金的重要手段。α相是铀的基态，但是这种正交相的稳定结构具有低对称性，导致了其很差的抗腐蚀、抗辐照性能和力学性能，而这不符合核反应堆和核武器制造的原料要求。人们往往通过在金属铀中添加合金化元素，使其全部或者部分发生相变，获得综合性能更好的γ相，从而获得具有实用意义的铀材料。铀合金的力学性能对于其使用性能具有十分重要的意义，因此，本文通过两种方法对其力学性能进行了研究：第一，本文运用基于第一性原理计算的张量团簇展开方法（general cluster expansion，GCE）计算了多种γ相铀基随机合金（铀钛、铀锆、铀铪、铀钒、铀铌、铀钽、铀钼）的弹性性质。第二，本文为了动态研究铀合金的力学性能，构建了铀铌钛三元势函数，并进行了拉伸的动力学模拟。 本文在使用GCE方法计算弹性常数时，主要研究对象是铀基二元随机固溶体，因为在有序度不太高的情况下合金的弹性常数主要由其成分决定，在本文中以团簇展开（cluster expansion，CE）形式为哈密顿量的蒙特卡洛模拟也验证了这一点。本文首次推导了基于GCE方法的张量性质在随机固溶体中的成分相关解析表达，并且，由该解析式求解的铀合金弹性常数与SQS模型计算的结果保持一致，在铀钼体系中也获得了实验数据的支持。根据计算结果，本文总结了各铀基体系中成分对其弹性模量的大小和弹性各向异性的影响，并且根据C'和马氏体相变方向的剪切模量变化，分析了VB族合金元素稳定铀合金γ相的原因。 本文的分子动力学模拟采用我们自己构建的角度相关的铀铌钛三元ADP势函数作为力场，进行了铀铌钛三元合金非晶形成能力和铀铌α相二元合金的拉伸模拟。从结果来看，铀铌钛三元体系中铀铌，铌钛二元合金均不能形成非晶，在成分三角形内的远铌端有小范围可能形成非晶的区域。在α相铀铌合金[100]方向的拉伸实验当中，观察到了大量的（110）孪晶，并且与（130）孪晶形成了一种不稳定的组态，这些孪晶在长时间弛豫后演变为了弯折变形。而铌的添加降低了该方向的杨氏模量，降低了屈服强度，并阻碍了孪生的发生，应力松弛减少，使得后续滑移的流变应力增大。

As an important nuclear material, uranium is one of the most important national strategic materials in both energy industry and weapon manufacturing. Because of the radioactivity of uranium materials and strict control of its use, the experimental research of uranium materials is very difficult, and the experimental data about uranium materials is also very scarce. Therefore, calculation and simulation become an important means to study uranium and uranium alloys. α phase (orthogonal) is the ground state of uranium, but this structure has low symmetry, which leads to its poor corrosion resistance, radiation resistance and mechanical properties. It does not meet the requirements of raw materials of nuclear reactor and nuclear weapon manufacturing. People often add alloying elements to metal uranium to make all or part of it undergo phase transformation and obtain γ phase with better comprehensive properties, in order to obtain uranium materials with practical significance. The mechanical properties of uranium alloys are very important for their performance, therefore, the mechanical properties of uranium alloys are studied by two methods in this paper: firstly, the elastic properties of various γ phase uranium based alloys (U-Ti, U-Zr, U-Hf, U-V, U-Nb, U-Ta, U-Mo) are calculated by tensor cluster expansion (GCE) method based on first principles calculation. Secondly, in order to study the mechanical properties dynamically of uranium alloys, the ternary potential function of uranium-niobium-titanium is constructed and the dynamic simulation of tension is carried out. In this paper, when using GCE method tocalculate the elastic constants, we use the random solid solutions of the γ phase uranium based binary, because the elastic constants of the alloys are mainly determined by its composition unless for high ordered alloys, which is also verified by the Monte Carlo simulation which using CE form Hamiltonian in this paper. What’s more, the composition dependent analytical expression of tensor properties in random solid solutions based on GCE method is derived for the first time. The elastic constants of uranium alloy calculated by the analytical expression are consistent with the results calculated by SQS model, which is also supported by experimental data in uranium molybdenum systems. According to the calculation results, this paper summarizes the influence of the composition of each uranium based system on its elastic modulus and elastic anisotropy. According to the change of of C ' and shear modulus in the direction of martensite transformation, the ability of stabilizing γ phase of uranium alloys of VB group alloy elements is analyzed and verified . In this work, the angle dependent ADP potential of U-Nb-Ti ternary alloys is used as the force field to simulate the amorphous forming ability of U-Nb-Ti ternary alloys and the tensile strength of U-Nb binary alloys. The results show that neither U-Nb nor Nb-Ti alloy can form amorphous in the ternary system, and there is a small area of amorphous in the composition triangle far from the Nb riched region. For tensile simulation, A large number of (110) twins were observed in the [100] direction tensile test, and formed an unstable configuration with (130) twins. These twins evolved into bending deformation after long time relaxation. The addition of niobium reduces the young's modulus and yield strength in this direction, hinders the occurrence of twinning, reduces stress relaxation, and increases the flow stress of subsequent slip.