Laser deposition of compositionally graded titanium-vanadium and titanium-molybdenum alloys

Compositionally graded binary titanium-vanadium and titanium-molybdenum alloys have been deposited using the laser engineered net-shaping (LENS(TM)) process. A compositional gradient, from elemental Ti to Ti-25at.% V or Ti-25at.%, Mo, has been achieved within a length of similar to 25 mm. The feedstock used for depositing the graded alloy consists of elemental Ti and V (or Mo) powders. Though the microstructural features across the graded alloy correspond to those typically observed in alpha/beta Ti alloys, the scale of the features is refined in a number of cases. Microhardness measurements across the graded samples exhibit an increase in hardness with increasing alloying content up to a composition of similar to 12% in case of Ti-xV and up to a composition of similar to 10% in case of the Ti-xMo alloys. Further increase in the alloying content resulted in a decrease in hardness for both the Ti-xV as well as the Ti-xMo alloys. A notable feature of these graded deposits is the large prior P grain size resulting from the directionally solidified nature of the microstructure. Thus, grains similar to 10 mm in length grows in a direction perpendicular to the substrate. The ability to achieve such substantial changes in composition across rather limited length makes this process a highly attractive candidate for combinatorial materials science studies. (C) 2003 Elsevier Science B.V. All rights reserved.