In-situ laser ultrasonic measurement of the hcp to bcc transformation in commercially pure titanium

In-situ measurement of the β to α phase transformation kinetics in a Ti-5553 alloy using laser ultrasonics

“…Assuming a spherical grain approximation, the number of β grains is estimated to be of order 3000 which is sufficient to presume a random grain orientation distribution in the probed volume [26]. This constitutes a critical aspect of the LUMet measurements to minimize potential effects of β crystallographic orientation on the ultrasound velocities, as the elastic constants in the bcc phase are highly anisotropic [18,22]. Fig.…”

“…Laser ultrasonics sensing (LUS) has been identified as a useful tool to measure phase transformations in metals and alloys [14][15][16][17][18][19]. In addition to being in-situ, it is a non-contact and non-destructive technique that permits real-time tracking of microstructure evolution during complex thermomechanical processing, which is advantageous from the industrial perspective.…”

“…Phase transitions can be determined by this technique because the ultrasound velocity depends on the elastic properties and density of the investigated material [20], which typically change with phase fractions and crystallographic texture. Although LUS has been developed in the past three decades, there is still a limited number of publications on the usage of this technique for phase transformation measurements in titanium and Ti-alloys [17][18][19]. Zamiri et al [17] observed the sensitivity of LUS in detecting phase transitions in a Ti-6Al-4V wt.% alloy during continuous heating.…”

“…However, investigations on the complete α+β → β transformation were not performed by Hinterlechner et al [19]. Variation in ultrasound velocity upon allotropic transformation was observed by Shinbine et al [18] during thermal cycling of pure titanium. Here, the velocity behavior was modeled assuming that its change is correlated to a volume-fraction-weighted average of individual constituents by a simple linear addition law, as proposed by Kruger and Damm for steels [16].…”

Investigation of the Microstructural Evolution during Hot Stamping of a Carburized Complex Phase Steel by Laser-Ultrasonics

“…The system utilizes a frequency-doubled Nd:YAG laser pulse to vaporize a small amount of material on the sample’s surface. The vaporization depth is only in the order of around 10 nm [ 23 ]. The thermomechanical pressure on the surface due to the ablation process generates an ultrasonic pulse in the sample.…”