## 3 Results and Discussion
### Mechanical Properties  
It can be seen from Figure 13 that the alloy 1 specimen and alloy 2 specimen have common characteristics of tensile and impact properties. The mechanical properties of alloy 1 specimen and alloy 2 specimen in the X direction are better than those in the Y and Z directions. During deposition, since the X direction is parallel to the direction of the deposited weld bead, the microstructural distribution in the X direction is relatively simple, and there is no cyclic alternation of fine grain zones, columnar crystal zones, and HAZ, so the mechanical properties in this direction are optimal [33]. In Figure 13a, the tensile strength of the alloy 1 specimen in the X, Y, and Z direction is 424 MPa, 389 MPa, and 380 MPa, respectively, with an average tensile strength of 398 MPa. In Figure 13b, the tensile strengths of the alloy 2 specimen in the X, Y, and Z directions were 864 MPa, 805 MPa, and 709 MPa, respectively, with an average tensile strength of 793 MPa. The average tensile strength of the alloy 2 specimen increased by about 99% compared with that of the alloy 1 specimen. However, the difference in tensile strength between the X and Z directions of the alloy 2 specimens is more significant. In the Z direction of the alloy 2 specimen, the HAZ, columnar zone, and fine grain zone are cyclically distributed, where some of the low melting point second-phase particles in the HAZ are dissolved in the matrix due to multiple thermal cycles, which weakens the pinning effect of the second phase particles in the HAZ to the grain boundaries and dislocations. Therefore, the HAZ in the Z direction of the alloy 2 specimen is prone to become the area of crack initiation and propagation during the tensile process, which leads to a decrease in tensile strength in the Z direction. The distribution of the microstructure and precipitated phase in the X direction of the alloy 2 specimen is relatively uniform, and the tendency to produce stress concentrations in the X direction is lower during the tensile process; therefore, the difference in tensile strength between the X and Z directions of the alloy 2 specimen is more significant. Figure 13c,d show the impact toughness of the alloy 1 specimen and alloy 2 specimen at room temperature and low temperature (\(-196\ ^{\circ}\)C), respectively. The average impact toughness of the alloy 1 specimen at room temperature and low temperature is \(107\ \mathrm{J/cm^{2}}\) and \(90\ \mathrm{J/cm^{2}}\), respectively, and the impact toughness of the alloy 2 specimen at room temperature and low temperature (\(-196\ ^{\circ}\)C) is \(151\ \mathrm{J/cm^{2}}\), \(111\ \mathrm{J/cm^{2}}\). The average impact toughness of the alloy 2 specimen was 39% and 23% higher than that of the alloy 1 specimen at room temperature and low temperature, respectively. Figure 14a,d show the stress-strain curves of the two specimens, where the average yield strengths of the alloy 1 specimen and alloy 2 specimen are 316 MPa and 603 MPa, respectively, and the average fracture elongation is 36.8% and 44.3%, respectively. According to the yield strength and tensile strength of the material, the yield ratio of the material can be calculated, and the yield ratio of the alloy 1 specimen and the alloy 2 specimen are 0.794 and 0.761, respectively, and the yield ratio of the alloy 2 specimen is smaller, indicating that the plastic reserve of the alloy 2 specimen is larger, and the risk of brittle fracture is lower. In addition, the tensile strength and fracture elongation of the alloy 2 specimen are higher than those of the alloy 1 specimen, which indicates that the comprehensive mechanical properties of the strength and plasticity of the alloy 2 specimen are higher. As can be seen from Figure 14b,c,e,f, there are a large number of dimples distributed on the tensile fractures of the alloy 2 and alloy 1 specimens, and there are no cleavage facets, which belong to the typical plastic fracture.