Solidification behavior of SiCf/Ti17 induced by fixed-point laser surface remelting

Abstract

Taking advantage of laser additive manufacturing, continuous SiC fiber reinforced titanium matrix composites (SiCf/TMCs) with low density and excellent mechanical properties can be used to hybrid-fabricate large components with complex shape for aerospace applications. However, due to the anisotropy in both microstructure and heat transfer ability, the high-density and rapid heat input from laser during hybrid manufacturing process will cause the non-uniform damage of fibers and various solidification microstructure in the molten pool. In order to understand the solidification behavior of molten pool in SiCf/Ti17 composites, the fixed-point laser surface remelting was used to bring in rapid and symmetrical heat input. With the decrease of temperature from center to edge of the molten pool, both fiber damage degree and the contents of Si and C elements in melt decreased. The solidification microstructure contains TiCx, Ti5Si3 and β-Ti, and their morphology varies according to the melt composition. SiC fibers act as heterogeneous nucleation sites for first solidified phases and promote their preference growth along the radial direction of fibers resulting from the excellent heat transfer ability. The faceted Ti5Si3 grains solidified through peritectic reaction L+TiCx→Ti5Si3 exhibit strong <0001> texture.