Effect of Substrate Temperature on Structure Formation in Titanium Alloy during Direct Laser Deposition

The paper analyzes the effect of substrate temperature on the shape, size, and orientation of grains in the structure of VT6 alloy samples formed by the method of direct laser deposition of powder. It was established that in the samples of titanium VT6 powder alloy, the following three characteristic structural zones are formed: a fine equiaxed grain zone, an oriented columnar grain zone, and a zone combining both types of grains. By preheating the substrate prior to sample growing, it became possible to reduce the length of the equiaxed grain zone, while increasing the width of the columnar grains. Cooling the substrate during the sample growing process made it possible to solidify metal from a heterophase state, which allowed preserving the structure of the initial powder. A method for preheating the substrate prior to sample growing and force-cooling it after applying the first several layers of powder is proposed. The new method made it possible to reduce the length of the equiaxed grain zone and increase the length of the columnar grain zone in the metal structure of the samples formed by direct laser deposition method.