Biomedical Engineering Reference
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(a)
(b)
Figure 9.19. (a) Lower magnifi cation and (b) higher magnifi cation backscatter SEM images
of LENS™ as-deposited TNZT + 2B alloy composites showing both coarser primary borides
exhibiting contrast within the same boride precipitate as well as fi ner scale eutectic borides.
[Sonia Samuel et al. Wear Resistance of Laser Deposited Boride Reinforced Ti - Nb - Zr - Ta Alloy
Composites for Orthopedic Implants (to appear in Mater. Sci. Eng. C, 2007)]
boride. In addition, the matrix also exhibits variations in contrast. Thus, while the
regions adjoining the primary boride precipitates exhibit a lighter contrast, the
regions a further distance exhibit a relatively darker contrast. There is also a clus-
tering of the eutectic boride precipitates within these regions of darker contrast,
as clearly visible in Figure 9.19b. SEM-EDS studies revealed that the composition
of the matrix to be Ti - 34%Nb - 7%Zr - 7%Ta (all in wt%). Figure 9.20 shows the
results of EDS studies carried out on one of the primary boride precipitates.
The SEM image of the specifi c boride precipitate analyzed is shown in Figure
9.20a together with the line across which the compositional variation was mea-
sured using SEM-EDS. The compositional profi le across this line is shown in
Figure 9.20b and has been divided into distinct zones within the boride precipi-
tate, exhibiting the different contrasts in Figure 9.20a. On either sides of the
boride, the composition of the matrix is Ti-33Nb-7Zr-9Ta which is marginally
enriched in Ta as compared with the average alloy composition (
7 wt% Ta). The
 
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