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In this study, the effects of solution treatment (ST) on the microstructure and anisotropic mechanical properties of Hastelloy X fabricated by laser directed energy deposition (L-DED) were investigated. The microstructure of the as-deposited (AD) sample presented coarse granular grains aligned with the deposition direction. Due to the segregation of Mo and Cr elements, a special cellular-structure was formed in the inter-dendritic region, along with the strip-like carbides consisting of both M 23 C 6 and M 6 C carbides. The cellular-structure homogenized rapidly after the ST. In detail, as the ST temperature increased, recrystallization generally occurred. Meanwhile, the strip carbides began to gradually dissolve and dissociate into dispersed particles which led to a drop in microhardness from 220 HV to 161 HV. The room temperature tensile results showed that the yield strength in the transversal direction (TD) and longitudinal direction (LD) decreased with the increase of ST temperature, reaching a minimum value of 285 MPa after the ST at 1175 °C. In addition, the ultimate tensile strength of the LD and TD samples reached maximum values of 693 MPa and 703 MPa at 1150 °C, respectively. It should be noted that the elongation of the low ductile TD sample can be improved significantly from 30% to 75% after the ST at 1175 °C. Therefore, it can be concluded that the anisotropy within the TD and LD samples can be effectively eliminated by controlling the cellular-structure, grain-structure, and carbide morphology during ST. • Cellular-structure is the major reason for anisotropic yield strength of as-deposited Hastelloy X. • Recrystallization during solution treatment could improve the anisotropic mechanical properties. • The dissolution of strip-like carbides benefits for enhancing the elongation of as-deposited Hastelloy X. [ABSTRACT FROM AUTHOR]

In this study, the laser repairing (LR) method is applied to 12Cr12Mo stainless steel, and the corresponding microstructural evolution, texture characteristic, and hardness variation are investigated. A 50/50 uniaxial tensile-test is conducted, and the mechanical failure mechanism is investigated using scanning electron microscope and transmission electron microscopy. The results show that the microstructure consists mainly of martensite and tiny M 23 C 6 carbide particles in the deposited zone (DZ), while the substrate contains tempered martensite and coarse M 23 C 6 carbide. The high laser-power generates a cubic texture in the DZ, while the substrate maintains a texture-free matrix. From the substrate to the DZ, the hardness increases sharply at the fusion line and then decreases gradually along the building direction. The tensile-test result indicates that the overall mechanical properties of LRed 12Cr12Mo stainless steel are comparable to wrought parts. Moreover, the microvoid-coalescence fracture indicates good plasticity of the LRed samples. Using this approach, we successfully repaired a 17th-stage stator cascade of a gas turbine, which indicates that LR can be used for the type of steel investigated in this study. • A defect-free metallurgical bonding could be obtained under both argon and air atmosphere during laser repairing. • The mechanical properties of laser repaired samples were comparable with those of the wrought substrate. • The 17th stage stator cascade of a gas turbine made from 12Cr12Mo steel was successfully repaired by laser repairing. [ABSTRACT FROM AUTHOR]

Solid-state refrigeration is considered a promising alternative to traditional vapor compression refrigeration technology. Researchers demonstrated that Ni–Mn–Ti alloys have a remarkable elastocaloric effect. However, the Ni–Mn–Ti alloy can only operate under a uniaxial stress field due to its antiferromagnetic austenite, which narrows its range of refrigeration temperatures. Here, we activated the magnetism of the alloy by replacing some Ni atoms with Co atoms. The Ni–Co–Mn–Ti–B alloy demonstrates a reversible maximum magnetic entropy change(Δ S m) of 24.9 J kg−1 K−1 and achieves an adiabatic temperature change of 7.8 K under a 7 T magnetic field. Additionally, we demonstrate that adding boron (0.2%) can improve the mechanical properties and cyclic stability in Ni–Mn–Ti alloys. The elastocaloric effect of 21.3 K with high cycle stability (1013 cycles) were successfully achieved in the directionally solidified (Ni 35 Co 15 Mn 35 Ti 15) 99.8 B 0.2 alloy. Furthermore, we have demonstrated that the magnetoelastic coupling effect can effectively extend the refrigeration temperature range. The alloys achieved large caloric effects in the temperature range of 240 K–340 K. This provides a new strategy for designing high-performance materials for wide-temperature-domain refrigeration. • The addition of Co activates the magnetic structure coupling of Ni–Mn–Ti alloy. The alloy exhibits a reversible maximum magnetic entropy change Δ S m of 24.9 Jkg −1 K −1 and achieves an adiabatic temperature change of 7.8 K under a 7 T magnetic field. • The addition of B can effectively improve the strength and ductility of the alloy. The material shows a highly stable (1013 cycles) elastocaloric effect of 21.3K. • The material can achieve a continuous refrigerable operating temperature range from 240 K to 340 K by combining elastocaloric, magnetocaloric and magnetoelastic coupling effects. • The stress-assisted method can not only improve the reversibility of caloric effect , but also broaden the temperature range of reversible caloric effect and improve the refrigeration performance of the active refrigerator. [ABSTRACT FROM AUTHOR]