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La précipitation à la solidification du monoborure de titane dans l'alliage de titane (Ti-6Al-4V) peut-elle modifier sa microstructure et son comportement mécanique ?

Abstract : This work concerns the precipitation of titanium monoboride (TiB) during solidification of titanium in order to increase its mechanicals properties. We have studies the TiB precipitation from Titanium and Ti-6Al-4V alloy. It was pointed out that the foundry, coupled with lost wax investment moulding, seems to be a promissing method to obtain a good improvement of mechanical properties of titanium alloys. Titanium foundry its generally associated with (i) coarse and heterogeneous microstructure (ii) oxygen contamination of the external layer of the piece and (iii) the problems linked to the melting of titanium (high melting point of titanium, high reactivity of titanium in a molten state). It has been showed that the boron incorporation does not need specific requirements ; moreover the effect of TiB is benefit for the titanium microstructure. TiB leads to a strong refinement of the titanium grain size. This refinement generally causes an increase of the mechanical properties. For Ti matrix, the UTS and YS are increased by a factor 2 with 3%Vo of TiB. In the case of Ti-6Al-4V matrix, the reinforcement effect is less important but it is still interesting and the best material is obtained with 0,5%Vo of TiB. The fracture surfaces show crystal of TiB cleaved along the b-axis. The cleavage of TiB crystals is at the origin of cracks appearance in the material.
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Submitted on : Friday, April 29, 2005 - 3:17:47 PM
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Frédéric Dartigues. La précipitation à la solidification du monoborure de titane dans l'alliage de titane (Ti-6Al-4V) peut-elle modifier sa microstructure et son comportement mécanique ?. Matériaux. Université Sciences et Technologies - Bordeaux I, 2004. Français. ⟨tel-00009144⟩

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