The bamboo boundary peak in an AlZr alloy

Abstract

An inverted torsion pendulum is used to study the high temperature internal friction of Al-0.073 wt% Zr alloy. Two internal friction peaks well separated from each other, the bamboo boundary peak and the conventional grain boundary peak, are observed in the original internal friction curve when the size of some grains is larger than the diameter of the specimen. The height of the bamboo boundary peak increases while that of the grain boundary peak decreases with increasing number of bamboo-like grains. The bamboo boundary peak in the completely bamboo-structured specimen decreases linearly in height with increasing size of bamboo grains, until the peak is completely absent in the single crystal specimen. The peak temperature of the bamboo boundary peak and the associated activation energy are 690 K (fp = 0.29 Hz) and 3.20 eV when bamboo grains coexist with fine grains, and 635 K (fp = 0.31 Hz) and 2.74 eV when the complete bamboo structure is formed, respectively. Combining the electron microscopic observation of the second phase particles in boundaries, it is suggested that the bamboo boundary peak is originated by the stress relaxation of the particle-bearing boundary.