Background subtraction method for relaxation spectra

C. L. MATTEO; G. I. ZELADA-LAMBRI; P. A. SORICHETTI; P. B. BOZZANO; O. A. LAMBRI; J. A. GARCÍA

Buenos Aires, Argentina

Congreso; 9° Congreso Internacional de Metalurgia y Materiales SAM-CONAMET 2009. Priemras Jornadas Internacionales de Materiales Nucelares; 2009

Sociedad Argentina de Materiales

Mechanical spectroscopy is a non-destructive technique which is a very useful method for studying the movement of dislocations and their interaction with point defects. However, spectra obtained at higher temperatures often show a noticeable background that obscure the interpretation of viscoelastic parameters. In this work a systematic procedure for background subtraction is presented, based on the mathematical properties of the complex elastic modulus. As an application, internal friction peaks of irradiated and nonirradiated molybdenum were studied in a wide range of temperatures. Molybdenum, a group VI transition metal has a melting point of 2883 K, high specific heat, and good corrosion and creep resistance. Also, it is ductile at room temperature, with a brittle-ductile transition temperature significantly lower than that of tungsten. Molybdenum has also good strength at high temperatures, being lighter than tungsten and tantalum, making it attractive for use in the nuclear industry. The only hypotheses about the background are that its general shape corresponds to the low temperature side of a relaxation peak and that it changes very little during measurements at different temperature cycles. Experimental results validate very satisfactorily the background subtraction method and the hypothesis on which it is based. The new procedure is very important for the study of the relaxation processes in refractory metals, but it can be also suitable to other kinds of materials and relaxation processes.