Influence of interpass cooling conditions on microstructure and tensile properties of Ti-6Al-4V parts manufactured by WAAM

Vázquez, L.; Rodríguez, N.; Rodriguez, Iker; Alberdi, E.; Álvarez, Pedro Gil

doi:10.1007/s40194-020-00921-3

Cited by 45 publications

(26 citation statements)

References 17 publications

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“…To prevent the oxidation of the AM parts produced using the WAAM process, it is necessary to provide a high argon gas flow rate. This, in turn, leads to significant forced convection cooling, and careful attention needs to be paid to thermal management and interpass conditions [13][14][15]. Oxidation and dissolved oxygen in the titanium matrix causes an undesirably rapid reduction in the fracture elongation and increases its strength due to solid-solution hardening [16,17].…”

Section: Introductionmentioning

confidence: 99%

Contactless temperature measurement in wire-based electron beam additive manufacturing Ti-6Al-4V

et al. 2021

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The complex thermal cycles and temperature distributions observed in additive manufacturing (AM) are of particular interest as these define the microstructure and the associated properties of the part being built. Due to the intrinsic, layer-by-layer material stacking performed, contact methods to measure temperature are not suitable, and contactless methods need to be considered. Contactless infrared irradiation techniques were applied by carrying out thermal imaging and point measurement methods using pyrometers to determine the spatial and temporal temperature distribution in wire-based electron beam AM. Due to the vacuum, additional challenges such as element evaporation must be overcome and additional shielding measures were taken to avoid interference with the contactless techniques. The emissivities were calibrated by thermocouple readings and geometric boundary conditions. Thermal cycles and temperature profiles were recorded during deposition; the temperature gradients are described and the associated temperature transients are derived. In the temperature range of the α+β field, the cooling rates fall within the range of 180 to 350 °C/s, and the microstructural characterisation indicates an associated expected transformation of β→α'+α with corresponding cooling rates. Fine acicular α and α’ formed and local misorientation was observed within α as a result of the temperature gradient and the formation of the α’.

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Section: Introductionmentioning

confidence: 99%

Contactless temperature measurement in wire-based electron beam additive manufacturing Ti-6Al-4V

et al. 2021

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“…Grain boundary α forms at the prior β-grain boundary and there is a preferred orientation between the grain boundary α and the primary β-grain [ 41 , 42 ], which leads to the formation of lamellar α-colonies with an average α-lath thickness of about 1 μm ( Figure 13 b,d,f). Vazquez et al [ 36 ] reported that this type of microstructure with the α-colonies along primary β-grains exhibits sufficient mechanical properties due to the assisted propagation of cracks along the thick α-colonies at the grain boundary. However, no significant difference between α-colony structures of the three different walls could be observed.…”

Section: Resultsmentioning

confidence: 99%

“…Thus, GMAW is utilized in Ti-WAAM less frequently than GTAW or PAW due to complications regarding the metal transfer of the Ti-wire during manufacturing. Several studies did not report any issues concerning metal transfer during Ti-WAAM using CMT [ 35 , 36 ]. Nevertheless, Pardal et al demonstrated that the effective wall width that could be produced by the CMT process is insufficient, which is why they applied a low-energy laser beam for arc stabilization and achieved positive results [ 37 ].…”

Section: Introductionmentioning

confidence: 99%

Gas Metal Arc Welding Modes in Wire Arc Additive Manufacturing of Ti-6Al-4V

et al. 2021

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In wire arc additive manufacturing of Ti-alloy parts (Ti-WAAM) gas metal arc welding (GMAW) can be applied for complex parts printing. However, due to the specific properties of Ti, GMAW of Ti-alloys is complicated. In this work, three different types of metal transfer modes during Ti-WAAM were investigated: Cold Metal Transfer, controlled short circuiting metal transfer, and self-regulated metal transfer at a direct current with a negative electrode. Metal transfer modes were studied using captured waveform and high-speed video analysis. Using these modes, three walls were manufactured; the geometry preservation stability was estimated and compared using effective wall width calculation, the microstructure was analyzed using optical microscopy. Transfer process data showed that arc wandering depends not only on cathode spot instabilities, but also on anode processing properties. Microstructure analysis showed that each produced wall consists of phases and structures inherent for Ti-WAAM. α-basketweave in the center of and α-colony on the grain boundary of epitaxially grown β-grains were found with heat affected zone bands along the height of the walls, so that the microstructure did not depend on metal transfer dramatically. However, the geometry preservation stability was higher in the wall, produced with controlled short circuiting metal transfer.

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“…By solving Equation (8), the proper interpass time that maintains a target interpass temperature T t is evaluated in Equation (9). The target interpass temperature for Ti-6Al-4V is assumed to be 400 • C in this study, as recommended [26][27][28][29]. Figure 10 shows proper interpass times estimated for different beads in order to maintain the target interpass temperature.…”

Section: Proposed Estimation Of Proper Interpass Time Using Regressiomentioning

confidence: 99%

“…Babu et al [1] re-simulated the DED process conducted by Denlinger et al [20] with the inclusion of a metallurgical model and obtained a similar trend of residual stresses according to the change of interpass time. It is critical to maintain a suitable interpass temperature because it influences the formation of the microstructure, porosity, geometric accuracy, and residual stresses within deposited parts [26][27][28][29].…”

Section: Introductionmentioning

confidence: 99%

Estimation Method of Interpass Time for the Control of Temperature during a Directed Energy Deposition Process of a Ti–6Al–4V Planar Layer

Chua

Ahn

2020

Materials

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Directed energy deposition (DED) provides a promising additive manufacturing method to fabricate and repair large metallic parts. However, it may suffer from excessive heat accumulation due to a high build rate, particularly during a wire feeding-type DED process. The implementation of interpass time in between two depositions of beads plays an important process role to passively control the interpass temperature. In this study, a method to estimate the proper interpass time using regression analysis from heat transfer finite element analysis is proposed for maintaining the interpass temperature during a wire feeding-type DED deposition of a planar layer. The overlapping beads of a planar layer are estimated using a polygonal-shaped bead profile in the finite element model. From the estimated proper interpass time, a selected proper interpass time scheme (PITS) is suggested for practical implementation. The selected PITS is applied in a thermo-mechanical finite element model to evaluate the temperature distribution and its effects on the depth of the melt pool, the depth of the heat-affected zone (HAZ), displacement, and residual stresses. By comparing the predicted results with those using a constant interpass time scheme (CITS), the selected PITS shows better control in reducing the depths of the melt pool and HAZ without severely inducing large displacement and residual stresses.

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Influence of interpass cooling conditions on microstructure and tensile properties of Ti-6Al-4V parts manufactured by WAAM

Cited by 45 publications

References 17 publications

Contactless temperature measurement in wire-based electron beam additive manufacturing Ti-6Al-4V

Contactless temperature measurement in wire-based electron beam additive manufacturing Ti-6Al-4V

Gas Metal Arc Welding Modes in Wire Arc Additive Manufacturing of Ti-6Al-4V

Estimation Method of Interpass Time for the Control of Temperature during a Directed Energy Deposition Process of a Ti–6Al–4V Planar Layer

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