2026 年 76 巻 3 号 p. 154-160
AA2618 aluminum alloy is well-known as an age-hardenable aluminum alloy with higher strength at elevated temperatures. In this study, the effect of dynamic precipitation on creep properties of AA2618 forged aluminum alloy was investigated by creep test, tensile test, transmission electron microscopy and differential scanning calorimetry. The differently aged three samples with varied yield stress: i.e. short-, middle- and long-aged samples, were prepared and then crept at 180°C under applied stress of 160-250 MPa. Although yield stress of short-aged sample was the lowest at room temperature and 180°C, the creep rupture time was the longest, and the minimum creep rate was the lowest among the three samples. Such a discrepancy between tensile and creep strength was attributed to dynamic precipitation in short-aged sample, in which newly formed precipitates during creep test compensate the softening induced by the growth and coarsening of existing GPB zones and S′/S phases. Therefore, it was clarified from this study that less stable precipitate microstructure with higher solute concentrations in the α-Al matrix of short-aged sample is good for creep resistance of this alloy system, although the tensile strength is lower than those of middle- and long-aged samples.
