Selective laser melting (SLM), a pivotal additive manufacturing (AM) technology for titanium alloys, enables near-net-shape forming of complex structures with relative densities of up to 99.9%, making it indispensable in aerospace, biomedical, and marine engineering. This review comprehensively updates the state of the art on SLM-fabricated TC4 (Ti-6Al-4V) alloy, addressing critical gaps in previous studies by integrating novel research progress, in-depth mechanistic analyses, and multi-dimensional comparisons. The core focus is on the unique thermal cycle (10⁶–10⁸ °C/s heating/cooling rates) of SLM, which induces a predominant needle-like martensitic α′ phase (99.7%) and minimal β phase (0.3%), leading to intrinsic anisotropy and low ductility. Room-temperature tensile strength reaches 1315.32 MPa with 9.6% elongation, and high-cycle fatigue limits the range from 417 to 829 MPa, strongly dependent on process parameters and post-treatment. Corrosion anisotropy is systematically analyzed: the XY plane (parallel to scanning direction) exhibits superior corrosion resistance in 1 M HCl (fewer pits and lower corrosion current density) and 3.5% NaCl (more stable passive film) compared to the XZ plane (deposition direction). Novel insights include: (1) synergistic effects of SLM process parameters (laser power–scanning speed–hatch spacing) on defect evolution and microstructure uniformity; (2) atomistic mechanisms of α′→α + β phase transformation during post-heat treatment; and (3) corrosion–mechanical coupling behavior in harsh environments (e.g., marine and biomedical). Post-treatment strategies are refined: annealing at 800 °C for 2 h achieves 1099 MPa tensile strength and 17.4% elongation, while hot isostatic pressing (HIP) reduces porosity from 0.08% to 0.01% and weakens fatigue anisotropy. This review also identifies unresolved challenges (e.g., in situ defect monitoring and multi-field regulated performance) and proposes future directions (e.g., AI-driven process optimization and functional gradient structures).

In this work, heat treatment of three different temperatures (600 °C, 800 °C, and 1000 °C) was applied to as-cast Al_0.75CoCr_1.25FeNi high-entropy alloys (HEAs) to investigate the influence of heat treatment on their corrosion properties. Open circuit potential (OCP) and cyclic polarization tests reveal that the 1000 °C heat-treated HEA possesses excellent corrosion resistance, as indicated by the low corrosion tendency and corrosion current density. Electrochemical impedance spectroscopy (EIS) and potentiostatic polarization analyses imply the presence of a superior passive film on the 1000 °C heat-treated HEA. X-ray photoelectron spectroscopy (XPS) analysis demonstrates that the passive film formed on the 1000 °C heat-treated HEA during potentiostatic polarization tests is most corrosion-resistant since it possesses the highest ratio of Al₂O₃/Al(OH)₃ and Cr₂O₃/Cr(OH)₃.

Friction stir welding (FSW) was employed to achieve a reliable joining of 2 mm thick dissimilar metals, 6061 aluminum alloy and AZ31B magnesium alloy. This study revealed the evolution of interfacial interlocking features and their impact on the mechanical properties of the joints under different welding speeds (25–35 mm/min). The results indicate that the Al/Mg FSW joint interface exhibits a strip-like interlaced structure, the morphological characteristics of which are closely related to the welding speed. For quantitative analysis, the ratio of interlocking length to plate thickness (embedding ratio) was used as a quantitative indicator of the structural interlocking feature. As the welding speed increased from 25 mm/min to 35 mm/min, the embedding ratio decreased from 13.2 to 7.9, and the average thickness of the intermetallic compound (IMC) layer decreased from 2.71 μm to 2.19 μm. Transmission Electron Microscopy (TEM) results confirmed that the Al/Mg FSW joint interface consists of a bilayer of IMCs, specifically Al₃Mg₂ and Al₁₂Mg₁₇, with thicknesses of 220 nm and 470 nm, respectively. Tensile testing of joints with different embedding ratios demonstrated that the tensile strength of the welded joint exhibits a positive correlation with the embedding ratio, reaching a maximum of 178 MPa.

Although the corrosion properties of Ti-6Al-4V have been widely studied, the differences in passive film evolution and corrosion mechanism between wrought and SLMed Ti-6Al-4V in acidic service environments are still unclear. In this work, the corrosion behaviors of wrought and selective laser melting (SLMed) Ti-6Al-4V alloys in 0.05 mol/L H₂SO₄ solution were systematically investigated using electrochemical impedance spectroscopy, potentiodynamic polarization curves, Mott–Schottky analysis and XPS depth profiling. Wrought and SLM-fabricated Ti-6Al-4V were selected to reveal the effects of typical forming processes on corrosion resistance, considering their wide applications and distinct microstructures. Electrochemical results demonstrate that the wrought alloy exhibits a higher polarization resistance, a thicker passive film, and a lower corrosion current density, corresponding to superior corrosion resistance. Mott–Schottky analysis reveals that the passive films formed on both alloys show n-type semiconductor characteristics, while the wrought alloy possesses a lower carrier concentration, fewer defects, and a more compact film structure. XPS depth analysis indicates that the content of TiO₂ in the passive films decreases with increasing etching depth, accompanied by an increase in TiOOH, TiO, and metallic Ti.

Zn-Ag alloys are deemed extremely promising materials for manufacturing biodegradable medical implants. Nonetheless, their practical applications are still constrained by inferior mechanical properties. To tackle this issue, Zn-0.5Ag alloy was alloyed with Mg (0.2 wt.%) and processed by combined equal-channel angular pressing (ECAP) and rolling, with different rolling reductions (40%, 60%, and 75%). ECAP-processed Zn-0.5Ag-0.2Mg alloy exhibited superior mechanical properties to its as-cast counterpart. Subsequent rolling of 40% further enhances the mechanical performance of ECAP-processed Zn-0.5Ag-0.2Mg alloy, with yield strength (YS), ultimate tensile strength (UTS), and elongation (EL) reaching 255 MPa, 309 MPa, and 52%, respectively, surpassing the application requirements. As the rolling reduction increased to 60% and further to 75%, YS and UTS declined, whereas EL rose continuously. The underlying mechanisms for the variation in strength and ductility were elucidated based on microstructure evolution analysis through optical microscopy (OM), scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD) characterizations.