Effect of solidification conditions and surface pores on the microstructure and columnar-to-equiaxed transition in solidification under microgravity

Yuze Li (1) , Nathalie Mangelinck-Noël (1) , G. Zimmermann (2) , Laszlo Sturz (2) , Henri Nguyen-Thi (1)

1 IM2NP - Institut des Matériaux, de Microélectronique et des Nanosciences de Provence
2 ACCESS (GERMANY)

Answer: Our objective is to characterize the effect of the grain structure on the eutectic percentage distribution with the measurements we perform, using a box size 0.5 mm along the solidification direction and 0.4 mm in width. The eutectic fraction measured at higher velocity in stage II is lower compared to the case at low velocity in stage I because the solidification proceeds by coarse columnar competitive growth at low velocity. Indeed, on the one hand, at low velocity, the competition with neighboring large dendrites with random orientation leads to the formation of quite large solute-enriched liquid pockets which are transformed into the eutectic phase at the end of solidification. On the other hand, in stage II, the microstructure at higher velocity, either columnar or equiaxed, is much finer due to the higher growth velocity, leading to a more uniform intergranular E% distribution. This phenomenon was discussed in more details for other experiments in our previous study [Liu et al. Acta Materialia, 64 (2014) 253]. As our focus was on the pore formation for the present article, we did not develop the discussion on this important aspect. We now mention in the text that eutectic percentage in relation to the grain structure is characterized and briefly explain the difference observed between stages I and II. Moreover, we added a reference to previous work in the text. We thank the reviewer again for this comment.

Domaines: Matériaux

Yuze Li, Nathalie Mangelinck-Noël, G. Zimmermann, Laszlo Sturz, Henri Nguyen-Thi. Effect of solidification conditions and surface pores on the microstructure and columnar-to-equiaxed transition in solidification under microgravity. Journal of Alloys and Compounds, 2018, 749, pp.344 - 354. ⟨10.1016/j.jallcom.2018.03.300⟩. ⟨hal-01850389⟩