Wire and arc additive manufacturing (WAAM) is a novel manufacturing technique in which large metal components can be fabricated layer by layer. In this study, the macrostructure, microstructure, and mechanical properties of a Ti-6Al-4V alloy after WAAM deposition have been investigated. The macrostructure of the arc-deposited Ti-6Al-4V was characterized by epitaxial growth of large columnar prior-β grains up through the deposited layers, while the microstructure consisted of fine Widmanstatten α in the upper deposited layers and a banded coarsened Widmanstatten lamella α in the lower layers. This structure developed due to the repeated rapid heating and cooling thermal cycling that occurs during the WAAM process. The average yield and ultimate tensile strengths of the as-deposited material were found to be slightly lower than those for a forged Ti-6Al-4V bar (MIL-T 9047); however, the ductility was similar and, importantly, the mean fatigue life was significantly higher. A small number of WAAM specimens exhibited early fatigue failure, which can be attributed to the rare occurrence of gas pores formed during deposition.

Microstructure and Mechanical Properties of Wire and Arc Additive Manufactured Ti-6Al-4V

Defect-interface interactions

Lengthscale-dependent, elastically anisotropic, physically-based hcp crystal plasticity: Application to cold-dwell fatigue in Ti alloys

Analysis of the different slip systems activated by tension in a α/β titanium alloy in relation with local crystallographic orientation

Spheroidization of the lamellar microstructure in Ti–6Al–4V alloy during warm deformation and annealing

Room temperature deformation and mechanisms of slip transmission in oriented single-colony crystals of an α/β titanium alloy

Creep occurs in two phase α/β Ti alloys at room temperature and at stresses below the yield strength. In polycrystalline Ti alloys, creep strain exhibits two distinct power-law regimes, an initial higher exponent which exhausts to a constant value at longer times. However, the exhaustion is much more gradual than that for other metals at lower homologous temperatures. The deformation mode in creep involves heterogeneous planar dislocation arrays. This paper describes the details of the dislocation processes and the observations of dislocation interaction with α/β interface boundaries in lamellar colony structures.

Mechanisms of primary creep in α/β titanium alloys at lower temperatures

Creep occurs in two phase α/β Ti alloys at room temperature and at stresses below the yield strength. Creep strains in the Widmanstatten structure are affected by colony size and by sliding at the α/β interfaces. This paper reports the results of an investigation on single colony crystals of a near a Ti alloy to understand the dependence of creep on the orientation of the α/β interface and the operative slip system. Associated mechanisms of slip transfer across the α/β interface and possible interface sliding are investigated and the results obtained are presented.

S. Suri

Papers

Room temperature deformation and mechanisms of slip transmission in oriented single-colony crystals of an α/β titanium alloy

Mechanisms of primary creep in α/β titanium alloys at lower temperatures

Effect of α/β Interfaces on Creep Behavior of Single Colony Titanium Alloys at Room Temperature