Work

Thermal behavior and microstructure control of Ti6Al4V alloy in laser directed energy deposition using synchronous gas cooling strategy

Year: 2026

Type: article

Abstract: Compared with conventional L-DED, synchronous gas cooling-assisted laser directed energy deposition (SGCL-DED) introduces a synchronous local cooling field during deposition, providing an additional strategy for active thermal-history regulation of Ti6Al4V alloy. This study investigates the effects of gas cooling flow rate on the thermal behavior, grain evolution, and phase structure of Ti6Al4V using experiments and numerical simulation. With increasing gas cooling flow rate, α′ martensite changes from acicular to lath-like morphology, with a reduced aspect ratio and improved size uniformity. The β grain size first decreases and then increases, while gas cooling promotes columnar grain growth. The crystallographic texture exhibits a non-monotonic variation, with the minimum α- and β-texture intensities occurring at 20 L·min -1 . Microhardness measurements demonstrate that synchronous gas cooling effectively improves the hardness of the deposited tracks, with the average hardness increasing from 500.3 HV without gas cooling to 581.8 and 584.1 HV at gas cooling flow rates of 20 and 40 L·min -1 , respectively. Temperature-field analysis shows that the cold jet produces a pronounced heat-sink effect, reduces the molten-pool peak temperature, and narrows the thermal influence zone and phase-transformation zone. The temperature gradient and solidification rate are also increased under gas cooling. Moreover, at gas cooling flow rates of 20 and 40 L·min -1 , the maximum temperature difference behind the cold-jet center decreases by 52.9% and 60.2%, respectively, indicating a substantial reduction in local temperature variation.

Source: Thermal Science and Engineering Progress

DOI: 10.1016/j.tsep.2026.104993