抄録
Effect of cold-working on the damping capacity of furnace-cooled or water-quenched Al–Zn alloys with 0–100%Zn was studied by varying the reduction in area. Measurements of the logarithmic decrement δ and the rigidity modulus G were carried out by the inverted torsion pendulum method at a frequency of 1 Hz. The hardness Hv and the specific weight S were measured by a micro-Vickers hardness tester and by the Archimedean method, respectively.
Except the water-quenched alloys with 70–90%Zn, the heat-treated alloys have generally a low value of δ. The magnitude of δ in the alloys subjected to the heat-treatment should be attributable to the viscous flow at the grain-boundary between the hard α and the soft β phases. Upon cold-working, the δ of any alloys, especially alloys with 50–70%Zn, considerably increases with reduction in area. The increase in δ must be mainly due to the increased boundary effect resulting from grain refinement.
The hardness of the alloys with 10–70%Zn water-quenched from 673 K is considerably higher than that of the alloys furnace-cooled. On the other hand, the furnace-cooled alloys with 80–90%Zn show a Hv value higher than the water-quenched ones. With approach to the eutectoid composition, the Hv value after cold-working decreases. The alloys water-quenched from 573 K or furnace-cooled from 573 and 673 K increase in G with Zn content, while those after water-quenching from 673 K yield a minimum value at 50%Zn. The G value after cold-working is nearly constant up to 40%Zn and increases rapidly with Zn content above 40%, regardless of the prior heat-treatment. The S increases with Zn content, but its value is generally as small as 4.8 Mg/m3 even for the Al-70%Zn alloy.
