The effects of rare earth element Sm on the microstructure, mechanical properties, and shape memory effect of the high temperature shape memory alloy, Cu-13.0Al-4.0Ni-xSm (x = 0, 0.2 and 0.5) (wt.%), are studied in this work. The results show that the Sm addition reduces the grain size of the Cu-13.0Al-4.0Ni alloy from millimeters to hundreds of microns. The microstructure of the Cu-13.0Al-4.0Ni-xSm alloys are composed of 18R and a face-centered cubic Sm-rich phase at room temperature. In addition, because the addition of the Sm element enhances the fine-grain strengthening effect, the mechanical properties and the shape memory effect of the Cu-13.0Al-4.0Ni alloy were greatly improved. When x = 0.5, the compressive fracture stress and the compressive fracture strain increased from 580 MPa, 10.5% to 1021 MPa, 14.8%, respectively. When the pre-strain is 10%, a reversible strain of 6.3% can be obtained for the Cu-13.0Al-4.0Ni-0.2Sm alloy.

A coating prepared via laser cladding has the advantages of a high-density reinforced layer, a low matrix dilution rate, and combination with matrix metallurgy. In this study, Ni₃Al-based alloy cladding layers with Cr₇C₃ were prepared via laser cladding, and the corresponding microstructures and wear resistance were studied in detail. The results show that the Ni₃Al-based cladding layer prepared using laser cladding technology had good metallurgical bonding with the matrix, and there were no pores, cracks, or other defects on the surface. The microstructures of the laser cladding layer were mainly γ′-Ni₃Al, β′-NiAl, and in situ C₇C₃. As the laser power increased, the heat input increased, resulting in an increase in the dilution rate. Simultaneously, the carbide size in the laser cladding layer increased. With the increase in laser power, the hardness of the laser cladding layer of the Ni₃Al-based alloy decreased, and the wear resistance of the laser cladding layer first strengthened and then weakened. When the laser power increased to 2.0 kW, the wear rate of the laser cladding layer decreased to 0.480 × 10⁻⁵ mm³/N·m. When the laser power increased to 2.4 kW, the wear rate of the laser cladding layer increased to 0.961 × 10⁻⁵ mm³/N·m, which was twice the rate at 2.0 kW. This could be attributed to small Cr₇C₃ particles, which could not effectively separate the wear pairs, resulting in more serious adhesive wear. Large Cr₇C₃ particles caused the surface of cast iron material with lower hardness to be damaged, which suffered more serious particle wear. The generation of short rod-shaped carbides should be avoided because, in the process of friction and wear, carbides with these shapes are easy to break, thus leading to crack initiation.

In this study, the influence of an aging treatment on the shape memory effect and martensitic transformation was investigated in an Fe–Mn–Al–Ni alloy by adding a small amount of Nb and C elements. Results show that the aging treatment can significantly improve the shape recovery rate of the alloy. In the bending test with 4% deformation, after aging at 200 °C for 1 h, the recovery rate increased from 20 to 45%, and it further increased to 51% after the two-step aging treatment at 800 and 200 °C. The high-temperature in situ X-ray diffraction and atomic force microscope were used to reveal the shape memory effect between room temperature and 400 °C in this alloy due to γ′→α transformation. The microstructure of aged specimens was investigated using transmission electron microscopy. With the extension of the aging time from 0.5 to 6 h, the size of NiAl precipitation gradually grew from 9 to 32 nm, and the distribution became more uniform. Meanwhile, the NbC particles were found in the two-step aging treatment alloy, which was the key to improving the shape memory effect.