Microstructure and Flame-resistant Properties of Ti-xV-15Cr (x = 20,25,30,35) Alloys by Laser Solid Forming

Abstract:

This paper details the production of a series of Ti-xV-15Cr (x=20,25,30,35) alloys by directed energy deposition (DED) technology, and pure Ti, pure V, and pure Cr powders were used as raw materials. The effects of V content on grain morphology, microhardness, elastic modulus and the flame-resistant properties of Ti-xV-15Cr alloys were determined. It was found that the microstructures of Ti-20V-15Cr, Ti-25V-15Cr and Ti-30V-15Cr alloys were composed of columnar grains growing epitaxially and fine equiaxed grains at the top region, with the aspect ratio of the columnar grains decreasing gradually with increasing V content. The microstructure of Ti-35V-15Cr alloy was composed of full near equiaxed grains except the very top region, which is very different from those of Ti-20V-15Cr, Ti-25V-15Cr and Ti-30V-15Cr alloys. The formation mechanism of microstructure was explained by combining the columnar to equiaxed transition (CET) model and the relationship between the height of the columnar grains layer and Z axis increment (ΔZ). The average microhardness of Ti-xV-15Cr alloys increases slightly with increasing V content, and the elastic modulus falls between 123.8 GPa to 137.6 GPa. Flame-resistant test showed that Ti-35V-15Cr alloy exhibits the best flame-resistant properties.

Key words:Ti-V-Cr alloys; microstructure; directed energy deposition; flame-resistant properties