Abstract: The thermal stability of rapidly solidified (RS) structures obtained in laser surface alloying on Ti-6Al-4 V with Pr is studied. The results show that the addition of Pr by laser can significantly increase the thermal stability of Ti-6Al-4 V below 800℃. It is due to the good resistance of RS structures to grain coarsening. TEM analysis indicates that 0.1-0, 4μm dispersed particles of the ordered phases containing Pr formed in the alloyed zone have the hexagonal close packed structure with a = 0.3914nm, c = 0.6592nm, c / a =1.684, and they are distributed in the interface of subcell in the primary columnar grains. During subsequent vacuum annealing, much finer precipitates of 10～20nm form on the dislocation lines and low angle boundaries. They are both beneficial to improving the thermal stability.

Key words: Laser allaying, Thermal stability, Ti-alloy