An approach to characterize the compositional, structural and mechanical properties of thermally processed titanium (Ti) alloy simultaneously via novel in-situ laser opto-ultrasonic dual detection (LOUD)

Abstract

A keen interest is developed in improving heat treatment methods of Ti alloy to meet the desirable mechanical properties due to its enhanced physical and chemical features. Structural and mechanical properties are important parameters as they are significantly affected by heat treatment and process conditions. However, most metal manufacturer relies on separate post-process analysis, which is usually time-consuming, costly, and destructive. Therefore, this study investigated a novel in-situ laser Opto-ultrasonic dual detection (LOUD) approach for real-time analysis of the elemental composition, grain size distribution, and hardness simultaneously of heat-treated Ti6AL4V alloy. The X-ray diffraction (XRD) and scanning electron microscope (SEM) results showed that with the increase in annealing temperature and cooling rate, a pronounced change in microstructure and phase transition occurs, eventually increasing grain size and hardness, respectively. The elemental composition, grain size distribution, and hardness variations were evaluated simultaneously via the processing of ultrasonic and optical signals in in-situ LOUD detection. The obtained results of average grain size from the ultrasonic acoustic attenuation of all the investigated samples are consistent with the results of optical microscope (OM) maps with a good regression coefficient value (R2 ≥0.991). Meanwhile, the optical spectral processing data for hardness analysis exhibited that the calibration curve of the emission intensity ratio (Ti-II/Ti-I) and plasma electron temperature (Te) is linearly dependent on hardness with (R2 ≥0.994). The linear correlation results of ultrasonic acoustic attenuation with grain size, calibration curve, and Te with the hardness investigated via the in-situ LOUD technique shows good approximation, ensuring quality control and reliability.