Dislocations in amorphous metals

The question of whether microscopic line defects such as dislocations can exist in amorphous metals is discussed. The discussion is divided into three parts. The first part is a general consideration of the existence, detection, identification, stability, and motion of dislocations. The second part summarizes the experimental indications including the shear band characteristics, shear step distribution, and reverse shear behavior. The third part reports the computer simulations on the stability and the motion of dislocations in a Lennard-Jones amorphous solid. The conclusion is that such dislocations may exist in amorphous solids but their characteristics remain to be identified. This paper is based on a presentation made at the symposium “50th Anniversary of the Introduction of Dislocations” held at the fall meeting of the TMS-AIME in Detroit, Michigan in October 1984 under the TMS-AIME Mechanical Metallurgy and Physical Metallurgy Committees.     

Measurement of Young’s modulus on small samples of amorphous metals using the impulse induced resonance technique

An impulse induced resonance technique capable of measuring the velocity of an ultrasonic extensional wave on a short (∼1 cm long) ribbonlike sample has been applied for the first time to the study of glassy metals; the Young’s modulusE was calculated from this velocity and the density. This technique is especially useful for measuringE on amorphous metal samples produced by the piston and anvil technique for rapid liquid quenching; standard techniques for measuringE are not readily applicable to such samples because of their small size. Details of the technique are given, and the dimensional limits necessary to avoid dispersion effects are discussed. The results agree well with those obtained by “pulse-echo” measurements on long ribbons. The Young’s moduli of two metallic glasses most readily prepared with the piston and anvil quenching technique are reported. L. T. KABACOFF, formerly Research Associate, Materials Science Division, Institute of Chemical Analysis, Applications and Forensic Science, Northeastern University, Boston, MA 02115. D. E. POLK, formerly Senior Scientist, Materials Science Division, Institute of Chemical Analysis, Applications and Forensic Science, Northeastern University, Boston, MA 02115