**Acknowledgements**

relationship between such quantities and the amount of nickel because this is not

*Microhardness and elastic modulus values for Ti-Ni alloy samples in homogenized condition, after hot rolling.*

*Recent Advancements in the Metallurgical Engineering and Electrodeposition*

chapter presented considerable variations of these factors.

A large variation in microhardness values was observed from 250 to 590 HV. Several factors influence a material's hardness: the concentration of substitutional and interstitial elements, microstructure, size of grain boundaries, types of phases, crystallographic orientation in which deformation occurs (since it involves a plastic deformation), and the type of processing [13]. The Ti-Ni alloy samples used in this

To analyze whether these values were in agreement with those found in the literature, it was used specifically by Chern Lin et al., with similar preparation of Ti-Ni alloys by arc melting and nickel concentration ranging from 18 to 28.4 wt%. The authors obtained microhardness values ranging from 300 to 390 HV [20]. In the present study, the microhardness ranged from 345 to 390 HV, values aligned approximately with Lin's study. For Ti-Ni alloys with nickel concentration varying

microhardness ranged from 270 to 510 HV due to the increase of Ti2Ni precipitates. Although the phases are different in relation to this study and other metallic atoms are present, the values are approximate with Lin's in relation to the other conditions, although the experimental parameters are not explicit in both cited studies. For the Ti15Ni alloy, a high value for the microhardness was observed. As mentioned earlier, the increase of the concentration of nickel, from the composition of about 6 wt%, does not act as a β-phase stabilizer but causes an increase in the temperature of the formation of intermetallic phase Ti2Ni that can be responsible for this increase in the hardness value [21]. In samples of Ti15Ni, a proeutectoid of Ti2Ni presents precipitates which probably reacted with oxygen, thus forming Ti4Ni2O, comparing the amount of nickel and precipitates. The formation

of Ti4Ni2O phase is another component to increase the hardness of the Ti15Ni alloy

The elastic modulus for Cp-Ti is around 95–105 GPa [9]. Thus, the addition of nickel caused a small increase in this property, probably from the addition of a new fcc phase referring to intermetallic Ti2Ni. However, as shown in **Figure 6**, it was not observed as a proportional ratio of the elastic modulus with the nickel

from 10 to 20 wt% obtained by laser fusion of metal powders [32], the

the only factor involved.

**Figure 6.**

[15, 21].

**20**

concentration.

The authors would like to acknowledge the Brazilian agencies Capes, for D. Cascadan's fellowship, CNPq (grants #481313/2012-5 and #307.279/2013-8), and FAPESP (grant #2015/25.562-7) for their financial support.
