<I>In Situ</I> Observations of Solidification and Melting of Aluminum Alloy Using Ultrasonic Waveguide Sensor

Abstract

The in situ observations of solidification and melting of an aluminum-silicon alloy (Al-12.6%Si) using an ultrasonic waveguide sensor are presented. The ultrasonic sensor consists of a conventional piezoelectric ultrasonic transducer, a cooling system and a titanium (Ti) rod as an ultrasonic waveguide. The sustainability of the Ti rod in the molten Al alloy is investigated by immersion tests for 1, 4, 8 and 16 h at 800 C. The formation of a layer consisting of globular TiAl 3 , disperse AlSi 2 Ti and -Al phases has been observed at the interface between the Ti and the Al alloy. Ultrasonic pulse-echo measurements of the Al alloy during solidification and melting have been performed using the ultrasonic sensor in temperature range from 200 to 800 C. The longitudinal wave velocity of the Al alloy shows a rapid and significant change from about 3900 to 5600 m/s around the eutectic point. An attempt to measure a solid/liquid interface of the Al alloy has been made at frequency of 2.25 MHz. The reflected echo from the interface undergoing directional solidification has been observed. The position and growth rate of the interface have also been determined from the reflected echo.

Development of the ultrasonic buffer rod for the molten glass measurement

“…In order to suppress the trailing echo, threaded or notched shape (Nagata et al, 1987;Sather, 1968), or tapered shape (Jen et al, 1997;Burthan et al, 2005) were employed in previous researches. Threading on the surface is intended to pseudo-randomly scatter the ultrasonic wave which impinges on the side wall.…”

“…In order to transmit ultrasound into high temperature media, a buffer rod technique has been widely used due to unavailability of high temperature transducer (Breeuwer et al,;Greenberg et al, 2008;Nagata et al, 1987;Prasad et al, 2008;Sather, 1968;Jen et al, 1997;Burthan et al, 2005). Many of them employed a through transmission method to comply with low signal-to-noise ratio (SNR) (Breeuwer et al,;Greenberg et al, 2008).…”

Ultrasonic generation by exciting electric arc: A tool for grain refinement in welding process

“…Quite a few researchers studied on the effect of ultrasonic during metal solidification, 4-6 but the previous methods of ultrasonic generation could not be introduced into welding pool. 7,8 As a special casting bath, welding pool has a tiny capacity and strong corrosive ability to amplitude transformer. The vibrations of welding wire and work piece were studied 9 to make the molten pool oscillate, but the devices were complex and inefficient.…”

A thickness mode acoustic wave sensor for measuring interface stiffness between two elastic materials

“…Compared with the conventional pulling method for bonding examination [11], the method to be proposed in this paper using acoustic wave sensors is much more accurate because, for high-frequency acoustic wave resonators, the frequency shift resolution is in terms of ppm (part per million). Compared with the acoustic wave sensors in [8] and [9] using propagating waves and measuring change of wave speed, we propose to use stationary waves and measure frequency shift, which has the advantage of being digital.…”

“…The effects of interface elasticity on vibration and wave propagation characteristics exhibited in [4]- [7] have motivated us to attempt the development of an acoustic wave interface elasticity sensor. Acoustic waves are widely used for sensing purposes, e.g., propagating waves are used in examining composites for interface damage [8] and monitoring metal melting and solidification processes [9], which have some relevance to the present paper. In [10], interface bonding using different glues was studied.…”