The relationship between an input energy density and the microstructure evolution of the Ti-6Al-4V alloy via laser remelting

Microstructure can affect the properties of the Ti-6Al-4V alloy. By defining the relationship between a microstructure evolution of the Ti-6Al-4V and an input energy density (IED) during laser remelting, it is possible to create an alloy with good surface quality and characteristics. Here, Ti-6Al-4V by laser remelting is obtained, containing transition beta phase, primary/secondary alpha phase, alpha-martensite, alpha'-martensite, and alpha ''-martensite. The plate transition beta phase appears at the grain boundary of martensite structures, cellular and columnar crystals. Only the beta -> alpha'-martensite transition occurs in the range of 20-40 J/mm2, while the beta -> alpha-martensite, beta -> alpha'-martensite, and beta -> alpha ''-martensite transitions occur simultaneously in the range of 40-100 J/mm2. As IED decreases, the coarse-plate alpha martensite decreases and acicular alpha' martensite increases. With the increase of IED, the grains in the melting zone of the specimen are larger, and the columnar crystals are easier to form in this zone. The results will provide a theoretical basis for surface modification of the titanium alloy by laser remelting technology to improve properties.