Untitled research work

Whether the G. P. zones change into intermediate phases (θ') was investigated by using a high resolution transmission electron microscope. Specimens were solution-treated at 520°C, quenched and subsequently aged at temperatures from 150 to 175°C for the time up to 104min. Either G. P. (2) zones in the binary alloy or G. P. (x2) zones in the ternary alloy corresponding to the above G. P. (2) zones were considered to transform continuously into θ' phases. Transformation in the ternary alloy was further accelerated than that in the binary alloy. In other words, in the ternary alloy, the aging time for the transformation was much shorter, and the dimension of G. P. (x2) zones when the transformation began to start was much smaller. At the edges of G. P.(x2) zones in the ternary alloy there precipitated Sn rich phases, being considered to play an important role for accelerating the transformation. The mechanism of G. P. zone→θ' transformation should be different in the binary and ternary alloys.