RESEARCH FOR CRYSTALLIZATION OF METALLIC-GLASS PD79.5NI4SI16.5

The monoenergetic slow positron beam was first used to study the cryst allization process of metallic glasses. The measurement of Doppler bro adening spectra as a function of positron beam energy was performed on the samples of the metallic glass Pd79.5Ni4Si16.5 with various states (i.e., the as-quenched state, structural relaxation states and crysta lline states). It is shown that there are a great number of the vacanc y-type defects in the as-quenched state sample. Its crystallization pr ocess starts at the sample surfaces. The present research indicates th at the slow positron annihilation spectroscopy (SPAS) is one of most e ffective methods for studying the crystallization process of metallic glasses.