IN718 alloy components are widely employed in high-temperature parts for aerospace applications. However, traditional machining methods are not only time-consuming but also lead to inefficient material utilization. This study introduces the fabrication of IN718 alloy through wire-laser directed energy deposition (W-LDED) technique. The alloy’s phase composition, microstructure, types of precipitated phases, and grain characteristics are characterized using X-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy, and electron backscatter diffraction. The mechanical properties of the alloy are evaluated using a universal tensile testing machine and a microhardness tester. The matrix of the IN718 alloy consists of the γ phase, with Laves precipitate phase located at the grain boundaries or sub-grain boundaries. Notable differences in surface microstructures and properties are observed across various planes. The XOY surface predominantly exhibits equiaxed grains with the smallest average grain size, whereas the XOZ and YOZ surfaces comprise a mix of equiaxed grains and coarse columnar grains, with the YOZ surface displaying the largest average grain size. The highest tensile strength, reaching 842.5 MPa, is recorded along the Y direction, accompanied by an elongation of 17.5%. Conversely, the highest elongation, at 29.5%, is noted in the X direction, with a tensile strength of 818.7 MPa. The hardness values of the XOY, XOZ, and YOZ surfaces are 314HV_0.2, 267HV_0.2, and 229HV_0.2, respectively.

Additive manufacturing of Hastelloy X superalloys remains challenges for practical aerospace applications due to the inadequate mechanical property at both ambient and high temperatures. To this end, this work proposes a novel Ta-modified strategy manipulating elemental segregation to stabilize cellular structures, thereby obtaining an outstanding combination between strength and ductility across a wide temperature regime. In particular, the tensile strength and elongation of Ta-modified superalloys can reach up to 1214 MPa and 28.4%, respectively, highly increased by 47% and 10% compared to original Hastelloy X superalloys at 25 ℃. Meanwhile, the tensile strength and elongation at 650 ℃ significantly increase to 843 MPa and 26.8% respectively, 38% and 150% stronger than their counterparts of the original Ta-free Hastelloy X superalloys at identical conditions. Microstructural observations reveal that prominent local segregation of Ta/Mo elements and in situ MC precipitates along cellular boundaries synergistically enhanced the stability of cellular structures. The stabilized cellular structures serve as continuous and skeleton-like networks during deformation, synergistically contributing to outstanding ductility and enhanced mechanical strength, as well as sustained strain-hardening ability. The present work provides new insights into an efficient alloy design method for additively manufactured nickel-based superalloys with outstanding mechanical property within a wide temperature regime.

Ni₅₁Ti₄₉ at.% bulk was additively manufactured by laser-directed energy deposition (DED) to reveal the microstructure evolution, phase distribution, and mechanical properties. It is found that the localized remelting, reheating, and heat accumulation during DED leads to the spatial heterogeneous distribution of columnar crystal and equiaxed crystal, a gradient distribution of Ni₄Ti₃ precipitates along the building direction, and preferential formation of Ni₄Ti₃ precipitates in the columnar zone. The austenite transformation finish temperature (A_f) varies from −12.65 ℃ (Z = 33 mm) to 60.35 ℃ (Z = 10 mm), corresponding to tensile yield strength (σ_0.2) changed from 120 ± 30 MPa to 570 ± 20 MPa, and functional properties changed from shape memory effect to superelasticity at room temperature. The sample in the Z = 20.4 mm height has the best plasticity of 9.6% and the best recoverable strain of 4.2%. This work provided insights and guidelines for the spatial characterization of DEDed NiTi.

The surface of copper-chromium alloy was processed by Al-Si-Ni multi-permeation and friction stir processing, and the microstructure and mechanical properties of the surface layer were tested by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), microhardness tester and friction testing machine. The results show that Al, Si and Ni elements are fully permeated into the surface of copper-chromium alloy after multielement co-infiltration and friction stir processing. In the observation of the microstructures, we found that the reticular structure is fragmented and distributed in the stir zone region. Microstructure becomes finer and grains refinement. The micro hardness of the copper-chromium alloy increased to 129 HV, 44.9% higher than that of the original matrix. The main reasons of microhardness enhancement are solid solution strengthening, fine grains strengthening and dispersion strengthening. The friction test results show that the friction coefficient is basically stable at 0.69 and the wear mass is only 0.0017 g after 10  min of friction test. The improvement of wear resistance was attributed to the increase of microhardness of the alloy surface.