Optimization of microstructure and properties of TB6 titanium alloy repaired by pulsed TIG additive manufacturing

Abstract

The defects on TB6 titanium alloy were repaired using pulsed TIG（tungsten inert gas） additive manufacturing technology， and the effects of process parameters （pulse current and pulse time） and heat treatment on the microstructure and mechanical properties of the repaired TB6 titanium alloy were studied to determine the optimal heat treatment process parameters. The results show that the mechanical properties are relatively better in the as-repaired state when the pulse current is 50 A and the pulse time is 40 ms， with a tensile strength of 1113 MPa and an elongation of 5.26%. These samples are sequentially subjected to solid solution and aging heat treatment. When the samples are solid solution treated for 2 h under different temperatures （740， 760， 780 ℃）， the primary α phase is increasingly dissolved， while the β phase gradually grows and evenly distributes in the matrix. After water quenching， the growth of the β phase is inhibited， and acicular rhombic martensite α'' phase is precipitated in β grains， resulting in a decrease in tensile strength and a remarkable increase in elongation. Under different aging temperatures （500， 520， 540 ℃） for 8 h， the α'' phase continuously grows and gradually transforms to equiaxial grain， and the mechanical properties are greatly improved. The optimal microstructure and mechanical properties are achieved under the conditions of 780 ℃/2 h WC+520 ℃/8 h AC， with a tensile strength of 1119 MPa and an elongation of 7.36%.

Keywords

• pulsed tig
• additive manufacturing
• tb6 titanium alloy
• microstructure
• mechanical property
• heat treatment