The aim of this study was to optimize machining parameters to obtain the smallest average surface roughness (Ra) and flank wear (Vb) values as a result of the surface milling of a nickel-titanium (NiTi) shape memory alloy (SMA) with uncoated cutting tools with different nose radius (r_ε) under dry cutting conditions. Tungsten carbide cutting tools with different r_ε (0.4 mm and 0.8 mm) were used in milling operations. The milling process was performed as lateral/surface cutting at three different cutting speeds (V_c) (20, 35 and 50 m/min), feed rates (f_z) (0.03, 0.07 and 0.14 mm/tooth) and a constant axial cutting depth (0.7 mm). The effects of machining parameters in milling experiments were investigated based on the Taguchi L18 (2¹ × 3²) orthogonal sequence, and the data obtained were analyzed using the Minitab 17 software. To determine the effects of processing parameters on Ra and Vb, analysis of variance (ANOVA) was used. The analysis results reveal that the dominant factor affecting the Ra is the cutting tool r_ε, while the main factor affecting Vb is the f_z. Since the predicted values and measured values are very close to each other, it can be said that optimization is correct according to the validation test results.

In the present study, the temperature-dependent pseudoelastic behavior of shape memory alloy (SMA) sheets is studied experimentally and by finite element (FE) modeling. For this purpose, temperature-dependent mechanical properties for Ni–Ti alloy materials are first obtained by using direct tensile and three-point bending experiments at 23 °C, 50 °C, and 80 °C temperatures, respectively. The structure of these materials is examined at different temperatures using SEM images and the XRD test. Furthermore, using the FE model, the pseudoelastic behavior and the effect of temperature on the residual deflection of the prose-shape memory strips with a circular hole under three-point bending loads are studied. After validating the results of the FE model with the results of experimental tests, the effects of various parameters such as the diameter and number of holes on residual deformation and residual strains are investigated. The results show that with increasing temperature, the mechanical properties including the tensile strength, Young’s modulus, yield stress, and flexural strength of SMA strips increase significantly. For solid strips, although increasing the temperature increases the maximum flexural force, in contrast, it reduces the flexural stiffness. In solid strips, flexural stiffness decreases by 5.5% with increasing temperature from 23 °C to 80 °C.

Nickel-Titanium (NiTi) alloys are widely applied in biomedical and industrial domains, mainly because of their unique superelastic characteristics and biocompatibility. However, their performance is often constrained by their tendency to wear and corrode, particularly under repetitive mechanical loading, harsh environmental conditions, and high friction coefficients. This study aims to reduce the wear rate and friction coefficient of NiTi alloys by forming oxide layers on the surface through heat treatment, while also increasing their corrosion resistance. It also examines the effects of high-temperature and prolonged heat treatments on surface performance. NiTi alloys were subjected to heat treatments at 900, 1000, and 1100?C for 2 and 4 hours. Wear tests were conducted using the ball-on-disc method under three different loads (5N, 10N, and 15N), three different test durations (30, 60 and 90 min), and at a constant speed of 0.05 m/s, to measure the friction coefficient and wear rates. Additionally, the alloys mechanical and corrosion performance was evaluated through microhardness and electrochemical corrosion tests. The results showed that samples treated at 1100?C for 4 hours exhibited a 146% increase in microhardness, reaching 640 HV, with the oxide layer thickness increasing to 462 ?m. This oxide layer reduced the wear rate by 60%, bringing it down to 150x10-6 mm?/Nm during a 30 min test under a 15N load, while the friction coefficient decreased by 58%, dropping to 0.30 ?. In contrast, nonheattreated samples exhibited lower hardness (260 HV), higher friction coefficients (0.72 ?), and greater wear rates (370x10-6 mm?/Nm) under a 5N load over a 90 min test. Corrosion analyses indicated that samples treated at higher temperatures showed more positive corrosion potentials and significantly improved corrosion resistance, with the best performance observed in samples treated at 1100?C for 4 hours. These findings suggest that the thick oxide layers formed during high-temperature, long-duration heat treatments significantly improve the wear resistance, reduce the friction coefficient, and enhance the corrosion resistance of NiTi alloys, making them more durable for industrial and biomedical applications.