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The structural and thermophysical characteristics of an Ni-rich NiTi alloy rod produced on a laboratory scale was studied. The soak temperature of the solution heat-treatment steps above 850 °C taking advantage of the precipitate dissolution to provide a matrix homogenization, but it takes many hours (24 to 48) when used without thermomechanical steps. Therefore, the suitable reheating to apply between the forging process steps is very important, because the product’s structural characteristics are dependent on the thermomechanical processing history, and the time required to expose the material to high temperatures during the processing is reduced. The structural characteristics were investigated after solution heat treatment at 900 °C and 950 °C for 120 min, and these heat treatments were compared with as-forged sample structural characteristics (one hot deformation step after 800 °C for a 30 min reheat stage). The phase-transformation temperatures were analyzed through differential scanning calorimetry (DSC), and the structural characterization was performed through synchrotron radiation-based X-ray diffraction (SR-XRD) at room temperature. It was observed that the solution heat treatment at 950 °C/120 min presents a lower martensitic reversion finish temperature (A_f); the matrix was fully austenitic; and it had a hardness of about 226 HV. Thus, this condition is the most suitable for the reheating stages between the hot forging-process steps to be applied to this alloy to produce materials that can display a superelasticity effect, for applications such as crack sensors or orthodontic archwires.

The present study aims to assess the superelasticity behavior in Ni-rich NiTi alloy wire produced by rotary forging process. The thermomechanical process involved four steps of hot working at 800ºC, two steps of cold working with solution heat treatment at 800ºC between them, and subsequently a solution heat treatment (950ºC during 2 hours) followed by aging treatment at 350, 400 and 450 ºC during 30 minutes. X-ray diffraction (XRD) and instrumented ultra-micro hardness testers evaluated the present phase at each aged sample and were compared with their mechanical behavior. The results put in evidence the work-hardening effect on a forged condition associated with the final step of cold rotary forging. The solution treatment promotes stress relaxation and precipitate dissolution. The sample heat-treated shows the presence of the precipitated (Ni4Ti3) and R phase. The presence of these precipitates is beneficial because precipitation-hardening increases the yield strength of austenite, which in turn contributes to better functional stability.

Hydroxyapatite is an essential material for bone and dental composition, widely used in biomaterials due to its biocompatibility and bioactivity. Its crystalline structure, similar to human bone, facilitates integration with biological tissues, promoting bone and dental regeneration. Applications include implants, orthopedic coatings, and bone grafts. The aim of this work was to synthesize hydroxyapatite with different percentages of lithium fluoride by aqueous precipitation. The produced powders were sintered at 1100 °C, and their properties were characterized by XRD, FTIR, and SEM. The results indicated the presence of fluorapatite and calcium oxide phases in the hydroxyapatite with lithium fluoride, with ion substitution occurring, while samples without LiF addition revealed the presence of hydroxyapatite and calcium oxide phases. SEM images showed that the samples with LiF addition exhibited morphological anisotropy, while pure hydroxyapatite samples showed equiaxed grains. The addition of LiF reduced the porosity of the samples after sintering. FTIR results indicated that fluoride ions replaced the hydroxyl groups originally present in the pure hydroxyapatite structure.

Additive manufacturing (AM) plays a crucial role in the development of NiTi alloys, enabling the creation of complex and customized structures while optimizing properties for various biomedical and industrial applications. The aim of this paper was to investigate the influence of laser scanning speed on laser-assisted reactive sintering of a mixture of No and Ti powders. The samples were sintered at two different beam speeds, 4 and 5 4 mm/s and their morphological and microstructural characteristics were investigated. Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX) and X-ray diffraction (XRD) analyses revealed the presence of intermetallic compounds rich in Ni and Ti for both scanning speeds; however, the scanning speed of 5 mm/s produced a microstructure with greater porosity, leading to a sintered body with poorer consolidation. Thus, employing a slower beam scanning of 4 mm/s seems to be a better alternative in the laser-assisted reactive sintering of NiTi alloys.

This work investigated the sintering of silicon carbide (SiC) with alumina (Al2O3) and yttria (Y2O3) additives by hot pressing. Mixtures of SiC with 1% and 5% Al2O3 and Y2O3 were used, pressed at 1800 °C and 1850 °C, resulting in specimens that were characterized in terms of density, microstructure, Vickers hardness and fracture toughness. The addition of 5% oxide additives provided greater densification and better mechanical properties. The temperature of 1800 °C proved to be the most effective for sintering due to the microstructure presented. The analysis revealed a homogeneous distribution of additives and grains, concluding that the 5% additive is considerably superior for increasing the densification and mechanical strength of SiC.