To further understand the reasons for the low ductility of the
Ti–16Nb (1500) samples, the fracture surface and longitudinal sections
of the fractured Ti–16Nb (1500) tensile specimens were
examined by SEM (Fig. 10). The fracture surface showed indications
of a brittle cleavage fracture exhibiting both dimples and
TiCx particles as shown in Fig. 10a. The size of these dimples was
similar to the pore size in Fig. 4d, and therefore it is assumed that
these dimples were pores lying open on the fracture surface.
Fig. 10b presents a longitudinal section of a zone from 0 to
120 lm depth beneath the fracture surface. Although it has been
reported that both pores and brittle TiCx particles can result in a
decrease of ductility of Ti alloys [30,31], microcracks were formed
preferentially in the regions of carbide particles lying along grain
boundaries. At a higher magnification (see Fig. 10c), the microcracks
initiated in the carbide particles were found perpendicular
to the tensile direction, due to the stress concentration at the brittle
titanium carbides under monotonic tensile loading. As a consequence,
the acicular brittle titanium carbide particles should be
responsible for
To further understand the reasons for the low ductility of theTi–16Nb (1500) samples, the fracture surface and longitudinal sectionsof the fractured Ti–16Nb (1500) tensile specimens wereexamined by SEM (Fig. 10). The fracture surface showed indicationsof a brittle cleavage fracture exhibiting both dimples andTiCx particles as shown in Fig. 10a. The size of these dimples wassimilar to the pore size in Fig. 4d, and therefore it is assumed thatthese dimples were pores lying open on the fracture surface.Fig. 10b presents a longitudinal section of a zone from 0 to120 lm depth beneath the fracture surface. Although it has beenreported that both pores and brittle TiCx particles can result in adecrease of ductility of Ti alloys [30,31], microcracks were formedpreferentially in the regions of carbide particles lying along grainboundaries. At a higher magnification (see Fig. 10c), the microcracksinitiated in the carbide particles were found perpendicularto the tensile direction, due to the stress concentration at the brittletitanium carbides under monotonic tensile loading. As a consequence,the acicular brittle titanium carbide particles should beresponsible for
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