Jie Chen

This work reports on a systematic investigation of the microstructure and comprehensive performance of Cu–Fe immiscible composite coatings prepared through the combination of mechanical alloying and laser cladding. The samples were characterized by scanning electron microscopy with an energy dispersive analysis, X-ray diffraction, a digital microhardness tester, a current tester, an electrochemical analyzer, and a magnetometer. The results show that the immiscible composite coatings are mainly composed of α-Fe particle dispersion in the ε-Cu matrix due to liquid phase separation, and this is exacerbated by the addition of more Fe content. Concentrated distribution of Fe-rich particles at either the top or bottom of the immiscible composite coatings is driven by the dominant mechanism of Marangoni and Stokes motion. With the increased fraction of Fe content, the microhardness and electrical resistivity increased, but with a degradation in corrosion resistance. With the increased ball milling time, the electrical resistivity increased, and the corrosion resistance improved. Compared to the medium-carbon steel substrate, the immiscible composite coatings can achieve an improved corrosion resistance, as well as a maximum saturated magnetization of 10.172 emu/g and the lowest coercivity at 17.249 Oe.

This work reports on systematic investigation of the microstructure and comprehensive performances of Cu–Fe immiscible composite coatings prepared through the combination of mechanical alloying and laser cladding. The samples were characterized by scanning electron microscopy with an energy dispersive analysis, X-ray diffraction, a digital microhardness tester, current tester, electrochemical analyzer and magnetometer. Results show that the immiscible composite coatings are mainly composed of α-Fe particles dispersion in the ε-Cu matrix due to liquid phase separation, and this is exacerbated in addition of more Fe contents. Concentrated distribution of Fe–rich particles at either the top or bottom of the immiscible composite coatings are driven by the dominant mechanism of Marangoni and Stokes motion. With the increased fraction of Fe content, the microhardness and electrical resistivity increased, but a degradation in corrosion resistance. With the increased ball milling time, the electrical resistivity increased and the corrosion resistance is improved. Compared to the medium-carbon steel substrate, the immiscible composite coatings can achieve an improved corrosion resistance, as well as a maximum saturated magnetization of 10.172 emu/g and lowest coercivity of 17.249 Oe.

This study investigated the impact of aging heat treatment time on the mechanical properties of NiTi triply periodic minimal surface structures fabricated through laser powder bed fusion. X-ray diffraction analysis results indicate that with increasing aging time, the NiTi2 phase precipitates while the content of the B19’ phase decreases. At 10 h of aging time, the Ni4Ti3 phase becomes evident in the sample. The differential scanning calorimeter results show that R phase transformation occurs, and the phase transformation temperature increases when the aging time reaches 6 h. Microhardness increases with aging time, peaking at 477.8 HV after 10 h. Compression experiment results reveal a maximum elastic modulus of 1262.82 MPa for the gyroid sheet-shaped structure achieved after 2 h. In addition, the superelasticity test indicates the highest recoverable strains at 2%, 4%, and 6% compressive strain for the gyroid rod-shaped structure after aging for 10 h. In cyclic compression experiments, the ratio of shape memory recovery increases from 40% at 0 h to 97% at 6 h. Fracture analysis results show that the transition in the fracture mechanism from brittle fracture to quasi-cleavage fracture occurs after aging heat treatment.