Microstructure formation of Ti-6Al-4 V in synchronous induction assisted laser deposition

Abstract

Laser deposition (LD) is a useful repair technique and in-situ microstructure control is significant. However, the ability of in-situ microstructural control is inevitably limited in LD. Introducing induction heating into laser deposition is a potential solution for this challenging issue. In this research, the synchronous induction assisted laser deposition of Ti-6Al-4 V alloy were conducted and a thermal analysis model was established to investigate the influences of laser and induction energy on the morphology and size of the grains, the phase, and the Vickers hardness. Results showed that both of the thickness of equiaxed grain zone and the width of columnar grains increased with increasing laser energy and induction energy. The fraction of α phase increases with increasing induction energy due to sharply reduction of cooling rate during the cooling period caused by the post-heating, while the fraction of martensite increased with increasing laser energy. The “800 W-600A” and “1000 W-300A” samples have similar β grain morphology and size but consist of different phase, which is very distinctive from usual laser deposition process. This novel discovery indicates a great potential of microstructure control, the grains and the phase can be controlled separately by adjusting the laser parameters and induction parameters. Keywords: Synchronous induction assisted laser deposition, Ti-6Al-4 V alloy, Microstructure, Thermal behavior, Mathematical model analysis