为提高40CrNi3MoV钢的力学性能，在40CrNi3MoV钢中添加Al、Cu元素，研究了调质处理后实验用钢中的NiAl、Cu析出行为及其对力学性能的影响。利用SEM、TEM和EDS等手段表征了NiAl和Cu析出相的成分、结构、尺寸和形貌，通过三维原子探针(3DAP)对析出相形成元素的分布特征进行表征，对比研究了实验用钢的力学性能。结果表明，只添加Al元素后实验用钢中形成与基体共格的B2-NiAl析出相，这些NiAl相主要在晶界处析出且尺寸较大；进一步添加Cu元素后，析出了与基体共格的bcc结构富Cu相，添加Cu后减少了大尺寸NiAl相在晶界处的析出，促进了晶内纳米级NiAl析出。实验用钢中的NiAl析出相和基体点阵错配度小，对抗拉强度提供了200 MPa强化增量；添加Cu后，均匀分布的细小富Cu相和被细化的NiAl相增加了对位错的阻碍作用，屈服强度进一步提高了200 MPa，然而大量细小高密度的NiAl和Cu析出相降低了拉伸过程中产生裂纹的临界应变，因此与只添加Al元素的实验用钢相比，抗拉强度并未提高。

With the continuous improvement of the pressure-bearing capacity of pressure vessels, higher requirements are put forward for the mechanical properties of materials. 40CrNi3MoV steel is a typical pressure-vessel steel, which mainly depends on carbide strengthening. To further improve its mechanical properties, Al and Cu were added to the material to form intermetallic compound precipitates for strengthening, then the precipitation behavior of NiAl and Cu and their effects on mechanical properties were studied. The size, composition, structure, and morphology of NiAl and Cu precipitates were characterized by SEM, TEM, and EDS. The distribution characteristics of precipitate-forming elements were characterized by three-dimensional atomic probe, and the mechanical properties of the experimental steel were compared. The results show that B2-NiAl precipitates coherent with the matrix are formed in the experimental steel after adding only Al. These NiAl precipitates are mainly precipitated at the grain boundaries and are large; after adding Cu, a bcc-ordered Cu-rich phase coherent with the matrix is precipitated. At this point, the large-scale precipitation of the NiAl phase at the grain boundaries is reduced and nanoscale NiAl precipitation is promoted in the crystal. The mismatch between the NiAl precipitates and the matrix lattice in the experimental steel is small, and the tensile strength increases by 200 MPa; The uniformly distributed, fine Cu-rich phase and the refined NiAl phase increase the resistance to dislocation, and the yield strength is also increased by 200 MPa. However, a large quantity of fine and high-density NiAl and Cu precipitates reduce the critical strain of cracks in the tensile process. Therefore, compared with the experimental steel with only Al added, the tensile strength is not improved.