Collapse of lamellar structure and stability with the addition of Misch metal (Mm) to the cast Ti–Al–Mo–Nb–(Mm) alloys
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Misch metal (Mm), consisting of Ce and La, was added to Ti–45Al–3Mo–2Nb alloys in order to investigate phase transformation and microstructural changes. The pseudo-binary phase diagram was estimated via PANDAT software™. The addition of Mm caused a decrease in both the fractions of α2/γ lamella and the β0 phase, and served as an important factor for a collapse of lamellar structures. In addition, Mm significantly decreased the colony size of the alloy, resulting in an increase in high-temperature tensile yield strength of ~ 40% for the alloys with 0.3 at% Mm at 800 °C. It appears that the addition of Mm affects the phase stability and increase the proportion of the γ phase. The microstructural changes, with respect to Mm additions, were discussed in terms of structural observations during isothermal heat treatments.
Financial support from DAPA (Defense Acquisition Program Administration) through ADD (Agency for Defense Development) in the Republic of Korea is gratefully acknowledged (Contract No. UD140063GD). Also, JSP appreciates partial financial support by Basic Science Research Program through the National Research Foundation of Republic of Korea (NRF) funded by the Ministry of Education, Science and Technology (Contract No. 2016R1D1A1A0991905).