In-situ measurements of L12 phase formasion by means of SR-SWAXS

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This research aims to establish a new experimental method to inquire into the kinetics of phase esparation accompanying first-order order-disorder transition by utilizing a synchrotron-radiation small-angle and medium (wide) -angle scattering technique (SR-SWAXS) .Time-resolved small-angle scattering technique with synchrotron radiation source has been used as a powerful tool to examine the fast kinetics of phase separation. The purpose of this project is to extend the time-resolved SR-SAXS methods to a higher scattering vector region, namely, around 100 spot, to investigate the kinetics of concomitant phase separation and L12 type ordering in Al-Li and other alloys.The present results are summarized as :1. The time-resolved SR-SWAXS method developed in the present study proved that ordering precedes the phase separation in the temperature region below ordering instability. However, a very small phase separation always exists from the very beginning of quench. The degree of coupling between phase separation and ordering should be not very strong, but whether there is no coupling at all is still an open question.2. During heating a well-aged Al-Li samples, the change in the SAS and 100 shows that the change in the DSC signal is directly related to the volume fraction of delta', and the double-peak shape of DSC curve simply comes from kinetic conditions.