The propose of this review was to summarize the advances in multi-scale surface technology of titanium implants to accelerate the osseointegration process. The several multi-scaled methods used for improving wettability, roughness, and bioactivity of implant surfaces are reviewed. In addition, macro-scale methods (e.g., 3D printing (3DP) and laser surface texturing (LST)), micro-scale (e.g., grit-blasting, acid-etching, and Sand-blasted, Large-grit, and Acid-etching (SLA)) and nano-scale methods (e.g., plasma-spraying and anodization) are also discussed, and these surfaces are known to have favorable properties in clinical applications. Functionalized coatings with organic and non-organic loadings suggest good prospects for the future of modern biotechnology. Nevertheless, because of high cost and low clinical validation, these partial coatings have not been commercially available so far. A large number of in vitro and in vivo investigations are necessary in order to obtain in-depth exploration about the efficiency of functional implant surfaces. The prospective titanium implants should possess the optimum chemistry, bionic characteristics, and standardized modern topographies to achieve rapid osseointegration.

Functional gradient materials (FGMs), as a modern group of materials, can provide multiple functions and are able to well mimic the hierarchical and gradient structure of natural systems. Because biomedical implants usually substitute the bone tissues and bone is an organic, natural FGM material, it seems quite reasonable to use the FGM concept in these applications. These FGMs have numerous advantages, including the ability to tailor the desired mechanical and biological response by producing various gradations, such as composition, porosity, and size; mitigating some limitations, such as stress-shielding effects; improving osseointegration; and enhancing electrochemical behavior and wear resistance. Although these are beneficial aspects, there is still a notable lack of comprehensive guidelines and standards. This paper aims to comprehensively review the current scenery of FGM metallic materials in the biomedical field, specifically its dental and orthopedic applications. It also introduces various processing methods, especially additive manufacturing methods that have a substantial impact on FGM production, mentioning its prospects and how FGMs can change the direction of both industry and biomedicine. Any improvement in FGM knowledge and technology can lead to big steps toward its industrialization and most notably for much better implant designs with more biocompatibility and similarity to natural tissues that enhance the quality of life for human beings.

As a high-efficiency and high-quality welding technology, laser-tungsten inert gas (laser–TIG) hybrid welding has been widely used in the aerospace and marine equipment industries. Through laser–TIG hybrid welding of TC4 titanium alloy, the effect of the current on the weld formation, the microstructure and mechanical properties of the arc zone, and the laser zone was studied. The results show that the molten pool in the arc zone will flow periodically, and the flow becomes more intense with an increase in the current, which will result in a finer grain size in the arc zone than in the laser zone, having the effect of eliminating pores. The spacing of the α′ martensite beams in the laser zone is narrower, with an average spacing of 0.41 μm. The β phase increases gradually with the increase in the current, which will lead to a downward trend in the average hardness of both zones. The average hardness value of the laser zone, containing more α′ martensite and less β phase, is slightly higher than that of the arc zone. The hardness uniformity of the laser zone is also significantly better than that of the arc zone. The tensile strength of the joint shows a trend of increasing first and then decreasing, and the joint with I = 50 A presented the highest tensile strength of 957.3 MPa, approaching 100% of the base metal, and fractured in the fusion zone.

Ultrasonic non-destructive and imaging testing using the line array method is conducted on titanium alloy bars and the sound field distribution of linear array transducer probes is simulated and analyzed. The simulation of the sound field distribution of titanium alloy bars with different diameters is performed by CIVA software. CIVA is used for sensitivity and parametric studies and it can quantify the response to expected defects and can perform different inspection strategies. In this study, the different diameter bars and various defects are simulated by considering different frequencies, element sizes and numbers, and the test platform is used to verify the standard bar. Finally, the bar with natural defects is tested and a detection scheme based on the ultrasonic phased array method is proposed. By the simulation of focusing beam distribution, the distribution of the beam focus in the flat bottom holes can be analyzed, this can help the selection of focusing mode in the detection process and enhance the signal-to-noise ratio of defect detection. The test results show that utilization of the line array transducer to scan the titanium alloy bar can effectively solve the problem of defect detection in the titanium alloy bars.

This study investigated the effects of prefabricated pore structures combined with hot isostatic pressing (HIP) on the densification and corrosion resistance of ZL205A cast aluminum alloy. Results indicate that a rational pore structure design prior to HIP significantly enhances densification efficiency and improves the service performance of aluminum alloy components. Unlike conventional HIP methods, where interconnected pores hinder complete densification due to internal pressure equilibrium, the introduction of sealed pores enhances the effective pressure differentia, significantly promoting creep-induced pore closure. Comprehensive characterization using SEM (Scanning Electron Microscope), EDS (Energy Dispersive X-ray Spectroscopy), XRD (X-ray Diffraction), nanoindentation, and electrochemical testing confirmed that the proposed strategy leads to grain rearrangement, reduced porosity, and the formation of a denser passivation film, significantly improving mechanical strength and corrosion resistance. Under HIP conditions of 525°C and 100 MPa, pre-drilled specimens exhibited significant pore closure. Corrosion resistance and mechanical properties were significantly improved compared to undrilled specimens. The research results show that adopting a reasonable pore structure design before hot isostatic pressing can significantly improve both densification efficiency and service performance of aluminum alloy components.

The effects of Mn/RE (Nd, Gd) multi-modification on the microstructure and high-temperature compressive creep properties of Mg–8.0Al alloys were investigated. The dominant intermetallic phases in the as-cast microstructure are β-Mg₁₇4Al₁₂, Al₂(Gd,Nd), Al₁₁(Gd,Nd)₃, Al₈(Gd,Nd)Mn₄, and Al₁₀Mn₂(Gd,Nd). The detailed structures of various intermetallics were revealed by TEM; the results indicate that Mn addition promotes grain refinement and facilitates the precipitation of lath-shaped and spherical β-Mg₁₇Al₁₂ in as-cast Mg–Al–RE alloys, resulting in increases in the tensile strength and elongation of the 1.0Mn alloy by 26.5% and 92.1%, respectively. Additionally, thermally stable micron-scale Al₈(Gd,Nd)Mn₄ and Al₁₂(Gd,Nd)₂Mn₅, along with dynamically precipitated spherical nano-sized AlGd and AlNd particles in the α-Mg matrix, were innovatively observed in compression-crept specimens tested at 200 °C and 60 MPa; these phases play a key role in improving high-temperature creep resistance. A significant finding is that excessive Mn addition deteriorates creep performance, which is attributed to excessive grain refinement and the consequent increase in the contribution of grain boundary sliding during creep. However, the negative effect of grain boundary sliding—caused by grain refinement—on creep performance can be balanced by the strengthening effect of Al–Mn–Gd phases and the dynamic precipitation of nanoscale Al–RE particles. This paper provides new insights for designing Mg–Al–Nd–Gd–Mn alloys with both excellent high-temperature creep resistance and significantly enhanced mechanical properties.