The Application of Pulse-Heating Calorimetry To Metal Systems

University Of Tennessee Knoxville, Knoxville TN

Investigators

Abstract

The objective of the project is to evaluate the applicability of a pulse-heating calorimeter to metal systems. The experimental apparatus allows the simultaneous determination of the electrical resistivity (r) and the specific heat (Cp) from room temperature to 1400 degrees C. An experiment, including processing the data, takes about an hour. This specimen in the form of a wire or rod is self-heated by a current from a programmable power supply controlled by a computer. This device can also be used to control the thermal history of the specimen. For example, isothermal aging can be conducted with r and the associated heat effects determined which occur during aging. Due to the high heating rate that can be employed, r and Cp can be determined for metastable states. This allows the calculation of the free energy of transformation, for example, for the ordering reaction in Ni4 Mo. If defects form during heating (e.g., vacancies), the associated heat effect causes an abnormal increase in Cp. The data can be analyzed to determine the energy of formation of the defects. This would be particularly applicable to intermetallic compounds, such as FeAl, NiAl, Laves phases, etc.