Dikky Burhan

In Situ Monitoring of Solid-Liquid Interface of Aluminum Alloy Using High-Temperature Ultrasonic Sensor

A high temperature ultrasonic sensor with a titanium buffer rod has been applied to the in situ monitoring of the solid-liquid interface of an aluminum alloy (Al-12.6%Si) during unidirectional solidification at 700°C. The ultrasonic sensor consists of a conventional piezoelectric transducer, a titanium buffer rod as an acoustic waveguide and a cooling system. Its length is approximately 300 mm. This ultrasonic sensor, because of the unique characteristics of titanium, provides not only good acoustic coupling to molten aluminum but also high-corrosion resistance. Pulse echo measurements in the molten aluminum alloy are performed using the sensor at 2.25 MHz. A clear reflected echo from a stable solid-liquid interface of the aluminum alloy has been successfully monitored. In addition, the reflected echo from the growing interface during unidirectional solidification has also been monitored. The growth rate of the interface was determined to be 0.12 mm/s from the monitored echo.

Ultrasonic in-line sensors for inclusion detection in liquid metals

A high temperature ultrasonic sensor for detecting inclusion particles in molten metals is presented. The sensor consists of a conventional piezoelectric transducer and a focused waveguide, and provides high spatial resolution measurements in molten metals in a pulse-echo mode at 10 MHz. A taper-shaped clad buffer rod is used as the waveguide. In order to design the waveguide, elastic wave propagation in the rod is evaluated by a numerical simulation using a finite difference method. Focusing ability of the acoustic lens fabricated at the end of the rod is also examined numerically. Using the developed sensor, backscattered echoes from alumina particles of 160 /spl mu/m suspended in molten aluminum at 1073 K have clearly been observed.

Ultrasonic in-situ monitoring of solidification and melting behaviors of an aluminum alloy

This paper presents a newly developed high temperature ultrasonic sensor (US) and its application to in-situ observation of Al alloy during solidification and melting in temperatures up to 800/spl deg/C. The US mainly consists of a conventional piezoelectric transducer and a Ti buffer rod as an acoustic waveguide. The length is 300 mm. This sensor, owing to the unique characteristics of Ti, is highly expected to provide not only high acoustic coupling to molten Al but also high corrosion resistance. It is demonstrated that the Ti buffer rod has superior sustainability and wettability to the molten Al alloy. Using the US, the changes of the longitudinal velocity of the Al alloy during solidification and melting have been monitored as a function of temperature. Furthermore, a clear reflected echo from the solid-liquid interface of the Al alloy has been observed. The movement of the reflected echo due to the growth of the solid-liquid interface has also been monitored during the cooling process. Thus, it is demonstrated that the developed US using a Ti rod is a promising tool for molten Al monitoring.

Ultrasonic In-Situ Monitoring of Aluminum Alloy During Solidification and Melting

In both research and production involving solidification of materials, it would be beneficial to have an in-situ, real-time characterization of the material properties during solidification process. In this work ultrasonic in-situ monitoring of aluminum alloy (Al-12.6%Si) during solidification and melting using a high temperature ultrasonic sensor is presented. The ultrasonic sensor used mainly consists of a conventional piezoelectric transducer, a titanium buffer rod as an acoustic waveguide and a cooling system. A steel reflector is assembled at the probing end of the sensor to make time-of-flight measurements. The sustainability of the sensor has been evaluated for long time immersion up to 16 hours in the molten aluminum alloy and the possible reaction at the outer wall of the titanium rod has been examined. It has been demonstrated that the titanium buffer rod has good wettability and sustainability to molten aluminum. Using the ultrasonic sensor, pulse echo measurements with the aluminum alloy have been performed in temperature range from 200 to 800 °C. The changes of the longitudinal velocity of the aluminum alloy during solidification and melting processes have been successfully monitored. In addition the change in the amplitude of reflected echoes during solidification is discussed.Copyright