Solidification texture, variant selection, and phase fraction in a spot-melt electron-beam powder bed fusion processed Ti-6Al-4V

In situ melt pool measurements for laser powder bed fusion using multi sensing and correlation analysis

“…A recent study by Kamath et al . 23 showed that the spot melt strategy could produce a more homogeneous microstructure (crystallographic texture and phase fraction) than the raster melt. Additionally, Nandwana and Lee 19 pointed out that depending on process conditions, the spot melt strategy can produce a larger melt pool than the raster melt strategy (thus, resulting in better remelting and bonding in the AM part).…”

The use of defects and compositional variations to elucidate physical phenomena in electron beam melted Ti-6Al-4V across scan strategies

“…Qualitatively, the random scan strategy sample has the largest α lath sizes as well as the highest fraction colony (Figure 4.9e and f), while the raster scan strategy sample has the smallest α laths and least fraction colony (Figure 4.9c and d). While a quantitative assessment of the microstructure was not conducted as part of this work, previous analyses have been published on these samples [27] as well as other samples from the same build [27,[135][136][137][138][139][140][141]155,156] supporting the qualitative conclusions. The difference in microstructure is primarily a result of cooling rate differences, with the raster sample cooling the fastest, enabling the formation of a basketweave structure, and the random sample cooling the slowest [27].…”

“…4.1), the raster sample L5 is expected to experience a higher aluminum loss comparatively. Generalizing, the raster melt pool is thought to reach a higher temperature than either of the point-melt pool varieties, given heat accumulation from adjacent linear melt pools and a more rapid re-melting cycle [27,140]. Based on the EDS results presented in Section 5.3, the aluminum difference is not dominated by melt pool morphology alone.…”

“…Recent publications on AM Ti-6Al-4V, and other AM materials, have focused on the characterization of materials states related to the thermomechanical cycles experienced during the AM process (i.e., the liquid-solid and solid-solid transformations resulting from the layer-bylayer nature of the process) [27,135,136,140,141]. While the cyclic nature of AM processes is important in setting the final microstructure, the interactions of the heat source, melt pool, and the surrounding chamber environment are equally important and have significant impacts on the resulting materials state.…”

“…Melt pool temperature is itself a factor of scanning strategy, speed, and power, and therefore will vary, particularly between the linear and point-melting strategies, which result in different melt pool morphologies. Generalizing, the linear melt pool is expected to have a higher temperature than either of the point-melt pool varieties, given heat accumulation from adjacent linear scans and a more rapid re-melting cycle [27,140]. As such, in the case of ideal vaporization, temperature is assumed to be nearly solely responsible for differences in aluminum content.…”