Al-Co系合金の減衰能におよぼす冷間加工の影響

Abstract

The effect of cold working on the logarithmic decrement δ and the mechanical properties were investigated for Al-Co alloys containing 0.2 to 10.0%Co. δ and the rigidity modulus G were measured at room temperatures with an inverted torsion pendulum, and the tensile strength σt with an Instron-type tensile testing machine.The heat-treated alloys showed a slight increase in δ by the Co addition, but the value of δ remained as low as 9×10−3. At the same Co concentration the value of δ after furnace cooling was somewhat higher than that after water quenching. By cold working after heat-treatments, the value of δ considerably increased with increasing reduction in cross-sectional area, RA, for all alloys. With the increase in Co concentration, the value of δ after cold working steeply increased at first and above 1%Co, δ showed saturation for small RA or tended to decrease for large RA. Moreover, the alloys cold-worked after furnace cooling were higher in δ than those cold-worked after water quenching. The increment in δ by cold working was considered to be due to a remarkable increase in dislocation density.With increasing Co concentration, both G and σt of the heat-treated specimens increased but σt became almost constant above 2%Co. Cold working after heat-treatments gave a decrease in G and an increase in σt.