*3.1.3 B4C*

The use of B4C offers considerable scope for diversification and development of in situ secondary phases (TiC and TiB). Hence, a wide range of studies intended to demonstrate the suitability of B4C as a source of B and C for in situ secondary phases, owing to its reactive behaviour with the Ti matrix. The B4C particles can trigger reactions whose products contribute to enhance the TMC properties. In this regard, TiC and TiB phases may expect to be observed and analysed in this type of TMCs. **Figure 9** shows the XRD patterns of the TMCs reinforced with B4C particles. It can be verified that the highest temperature of the iHP process and the holding time (15 minutes) were insufficient for a full reaction between the boron carbide particles and the titanium matrices, even at the lowest concentration of B4C. Thus, this fact occurred independently of the starting compositions, confirmed by the


#### **Table 5.**

*RIR semi-quantification analysis of TMCs made from Ti-B4C blends, manufactured at different temperatures (by iHP).*

**109**

**Figure 10.**

*(c) 30 vol.% of B4C.*

*In Situ Titanium Composites: XRD Study of Secondary Phases Tied to the Processing Conditions…*

existence of peaks related to the boron carbide. Likewise, there were observed peaks

The microstructural study shows the homogenous dispersion of the B4C particles in the matrix. In this context, there were no agglomerations visually detected. This suggests that there was no porosity related to particles agglomerations as commented previously in TMCs reinforced by TiB2 and TiC. It could be considered as an advantage of the B4C as reinforcement in comparison with other ceramic particles. **Figure 11** shows TMCs processed at the same temperature with different B4C percentages.

Regarding the processing temperature, there were significant differences related to the reaction between the matrix and the B and C from the B4C particles. At the lowest temperature (1000°C), the formation of the in situ TiB and TiC phases was proportional to the starting content of B4C. Employing 10 vol.% of B4C, small proportions of in situ phases were detected (see **Table 5**). However, increasing the temperature to 1100°C and using 10 vol.% of B4C, the percentage of in situ TiC phase doubled its value, also, by the employment of 20 and 30 vol.%. This is in agreement with the intensity of the peaks of this phase in the TMC patterns (**Figure 10**). As expected, the major in situ formation of secondary phases took place at 1200°C. **Figure 12** reveals how the in situ phases surrounded the B4C particles, being a reaction layer clearly defined. Obviously, the higher the starting B4C composition, the more

*XRD patterns of TMCs reinforced in the starting blend with (a) 10 vol.% of B4C, (b) 20 vol.% of B4C, and* 

The intensification of TiB and TiC peaks from 1000 to 1200°C reflects the increase in the volume fraction of these phases, which can also be seen in the RIR

*DOI: http://dx.doi.org/10.5772/intechopen.88625*

matching TiB and TiC patterns.

analysis shown in **Table 5**.

*In Situ Titanium Composites: XRD Study of Secondary Phases Tied to the Processing Conditions… DOI: http://dx.doi.org/10.5772/intechopen.88625*

existence of peaks related to the boron carbide. Likewise, there were observed peaks matching TiB and TiC patterns.

The intensification of TiB and TiC peaks from 1000 to 1200°C reflects the increase in the volume fraction of these phases, which can also be seen in the RIR analysis shown in **Table 5**.

The microstructural study shows the homogenous dispersion of the B4C particles in the matrix. In this context, there were no agglomerations visually detected. This suggests that there was no porosity related to particles agglomerations as commented previously in TMCs reinforced by TiB2 and TiC. It could be considered as an advantage of the B4C as reinforcement in comparison with other ceramic particles. **Figure 11** shows TMCs processed at the same temperature with different B4C percentages.

Regarding the processing temperature, there were significant differences related to the reaction between the matrix and the B and C from the B4C particles. At the lowest temperature (1000°C), the formation of the in situ TiB and TiC phases was proportional to the starting content of B4C. Employing 10 vol.% of B4C, small proportions of in situ phases were detected (see **Table 5**). However, increasing the temperature to 1100°C and using 10 vol.% of B4C, the percentage of in situ TiC phase doubled its value, also, by the employment of 20 and 30 vol.%. This is in agreement with the intensity of the peaks of this phase in the TMC patterns (**Figure 10**). As expected, the major in situ formation of secondary phases took place at 1200°C.

**Figure 12** reveals how the in situ phases surrounded the B4C particles, being a reaction layer clearly defined. Obviously, the higher the starting B4C composition, the more

#### **Figure 10.**

*XRD patterns of TMCs reinforced in the starting blend with (a) 10 vol.% of B4C, (b) 20 vol.% of B4C, and (c) 30 vol.% of B4C.*

*Inelastic X-Ray Scattering and X-Ray Powder Diffraction Applications*

*SEM image of TMC with 10 vol.% of TiB2 in the starting blend, processed at 1200°C.*

rounded by the in situ TiBx phases.

*3.1.3 B4C*

**Ti matrix and B4C**

**Figure 9.**

The rising in temperature was crucial for reactions between the matrix and the TiB2 particles. At 1200°C, there were major diffusion of B through the matrix and more formation of the in situ TiBx phases. **Figure 9** shows two different areas on a cross section (iHP at 1200°C), where the B distribution varied considerably; the darkest region in the centre corresponds with the highest concentration of B. It suggests that the dark grey areas were originally the TiB2 particles, which were sur-

The use of B4C offers considerable scope for diversification and development of in situ secondary phases (TiC and TiB). Hence, a wide range of studies intended to demonstrate the suitability of B4C as a source of B and C for in situ secondary phases, owing to its reactive behaviour with the Ti matrix. The B4C particles can trigger reactions whose products contribute to enhance the TMC properties. In this regard, TiC and TiB phases may expect to be observed and analysed in this type of TMCs. **Figure 9** shows the XRD patterns of the TMCs reinforced with B4C particles. It can be verified that the highest temperature of the iHP process and the holding time (15 minutes) were insufficient for a full reaction between the boron carbide particles and the titanium matrices, even at the lowest concentration of B4C. Thus, this fact occurred independently of the starting compositions, confirmed by the

Temperature [°C] B4C vol.% Ti (%) B4C (%) TiB (%) TiC (%) 1000 10 92.2 5.7 1.6 0.5

1100 10 90.6 5.7 2.7 1.0

1200 10 89.0 4.9 5.0 1.1

*RIR semi-quantification analysis of TMCs made from Ti-B4C blends, manufactured at different temperatures* 

20 86.4 10.8 1.8 1.0 30 78.0 18.3 2.2 1.5

20 81.2 10.3 6.5 2.0 30 73.3 17.9 6.5 2.3

20 80.6 10.0 7.0 2.3 30 64.4 17.1 14.3 4.2

**108**

**Table 5.**

*(by iHP).*

**Figure 11.**

*SEM images of TMCs produced at 1000°C with (a) 10 vol.% of B4C, (b) 20 vol.% of B4C, and (c) 30 vol.% of B4C.*

#### **Figure 12.**

*SEM images of TMCs produced at 1200°C with (a) 10 vol.% B4C, (b) 20 vol.% B4C, and (c) 30 vol.% B4C.*

#### **Figure 13.**

*Hardness (HV2) and Young modulus values vs. operational temperature of the TMCs made from the different blends.*

the formation of in situ phases. Regardless of the starting compositions, the morphologies of the in situ phases TiC and TiB are similar to the ones observed previously. On the one hand, there were precipitates with the particular whisker shape of TiB in the matrix. On the other hand, the presence of TiC can be seen as globular precipitated; both in situ phase morphologies have been wide and thoroughly studied [32].

#### **3.2 Physical properties of the TMCs.**

The relative density of the specimens was around 99.5% in the majority of the specimens, even in those whose microstructures had a few pores. It means that the processing parameters were suitable to achieve full densification.

As expected, the highest values of hardness and Young modulus were recorded in specimens whose starting blends were made from the highest ceramic particle contents. **Figure 13** shows a comparison of the hardness and Young modulus values of the TMCs produced at the three processing temperatures (1000, 1100, and 1200°C) and using the three compositions (10, 20, and 30 vol.%).

The operational temperature contributed to enhancing the hardness and the Young modulus; however, its influence varied depending on the type of ceramic particles employed in the starting blend, as reflected in **Figure 13**. TMCs reinforced by

**111**

*In Situ Titanium Composites: XRD Study of Secondary Phases Tied to the Processing Conditions…*

TiB-TiB2 phases showed the highest hardness measured. This development is closely related to the content of in situ formed TiB. Although there was also in situ formed TiB in TMCs made from blends with B4C particles, the maximum percentage formed (14 vol.%) in these specimens was lower than in TMCs made from the blend with TiB2 (20 vol.%). In both cases, the TMCs were processed at 1200°C and 30 vol.%. In similar conditions, the highest Young modulus was also observed in TMCs reinforced

In specimens made from blends with TiC, the main variation was only caused by the addition of more TiC content. Hardness and Young modulus values hardly increased by temperature, despite the diffusion of the C in the matrix and the

Contrary to common thinking, the B4C reinforcement did not behave as the best precursor of in situ phases. Consequently, the expected properties may vary from the obtained values of hardness and Young modulus. The TiC and TiB formed were slightly lower than the in situ TiB formed in TMCs with TiB2. That means that the diffusion of B alone was major and the C could decelerate such diffusion. Furthermore, it should be highlighted that in specimens made from B4C, the values of hardness and Young modulus showed a wide standard deviation. This could be related to the in situ formed precipitates and their dispersion in the matrix.

The conclusions of the current study which analyse the influence of the starting

• Reinforcing the titanium matrix with ceramic materials results in an enhancement of the TMC mechanical properties caused by the formation of in situ

• XRD analysis states that the diffusion phenomenon of B and C elements into the matrix increases by the rising temperature; it is becoming increasingly

• In evaluating the appropriateness of the operational parameters, the lower the temperature, the less the reactivity reinforcement matrix. This phenomenon was more significant when the concentration of reinforcement was the

• The highest hardness and Young modulus of the TMCs were measured in

• The densification of the specimens was achieved at the processing parameters

The authors gratefully acknowledge the company "RHP-Technology GmbH" and

the managers Dr. Neubauer and Dipl. Eng. Kitzmantel for their partial financial support of this work. In addition, the authors want to thank the Universidad de Sevilla for the use of experimental facilitates at CITIUS Microscopy and X-Ray Laboratory Services (VI PPIT-2018-I.5 EVA MARÍA PÉREZ SORIANO).

materials and operational temperature in the TMC properties are drawn:

important in the apparition of secondary phases.

specimens reinforced by TiB2 particles.

with TiB-TiB2 phases, in agreement with the commented results above.

*DOI: http://dx.doi.org/10.5772/intechopen.88625*

TiC0.67 formed.

**4. Conclusions**

phases.

lowest one.

tested.

**Acknowledgements**

*In Situ Titanium Composites: XRD Study of Secondary Phases Tied to the Processing Conditions… DOI: http://dx.doi.org/10.5772/intechopen.88625*

TiB-TiB2 phases showed the highest hardness measured. This development is closely related to the content of in situ formed TiB. Although there was also in situ formed TiB in TMCs made from blends with B4C particles, the maximum percentage formed (14 vol.%) in these specimens was lower than in TMCs made from the blend with TiB2 (20 vol.%). In both cases, the TMCs were processed at 1200°C and 30 vol.%. In similar conditions, the highest Young modulus was also observed in TMCs reinforced with TiB-TiB2 phases, in agreement with the commented results above.

In specimens made from blends with TiC, the main variation was only caused by the addition of more TiC content. Hardness and Young modulus values hardly increased by temperature, despite the diffusion of the C in the matrix and the TiC0.67 formed.

Contrary to common thinking, the B4C reinforcement did not behave as the best precursor of in situ phases. Consequently, the expected properties may vary from the obtained values of hardness and Young modulus. The TiC and TiB formed were slightly lower than the in situ TiB formed in TMCs with TiB2. That means that the diffusion of B alone was major and the C could decelerate such diffusion. Furthermore, it should be highlighted that in specimens made from B4C, the values of hardness and Young modulus showed a wide standard deviation. This could be related to the in situ formed precipitates and their dispersion in the matrix.

## **4. Conclusions**

*Inelastic X-Ray Scattering and X-Ray Powder Diffraction Applications*

the formation of in situ phases. Regardless of the starting compositions, the morphologies of the in situ phases TiC and TiB are similar to the ones observed previously. On the one hand, there were precipitates with the particular whisker shape of TiB in the matrix. On the other hand, the presence of TiC can be seen as globular precipitated; both in situ phase morphologies have been wide and thoroughly studied [32].

*Hardness (HV2) and Young modulus values vs. operational temperature of the TMCs made from the different* 

*SEM images of TMCs produced at 1000°C with (a) 10 vol.% of B4C, (b) 20 vol.% of B4C, and (c) 30 vol.% of B4C.*

*SEM images of TMCs produced at 1200°C with (a) 10 vol.% B4C, (b) 20 vol.% B4C, and (c) 30 vol.% B4C.*

The relative density of the specimens was around 99.5% in the majority of the specimens, even in those whose microstructures had a few pores. It means that the

As expected, the highest values of hardness and Young modulus were recorded in specimens whose starting blends were made from the highest ceramic particle contents. **Figure 13** shows a comparison of the hardness and Young modulus values of the TMCs produced at the three processing temperatures (1000, 1100, and

The operational temperature contributed to enhancing the hardness and the Young modulus; however, its influence varied depending on the type of ceramic particles employed in the starting blend, as reflected in **Figure 13**. TMCs reinforced by

processing parameters were suitable to achieve full densification.

1200°C) and using the three compositions (10, 20, and 30 vol.%).

**110**

**Figure 11.**

**Figure 12.**

**Figure 13.**

*blends.*

**3.2 Physical properties of the TMCs.**

The conclusions of the current study which analyse the influence of the starting materials and operational temperature in the TMC properties are drawn:


### **Acknowledgements**

The authors gratefully acknowledge the company "RHP-Technology GmbH" and the managers Dr. Neubauer and Dipl. Eng. Kitzmantel for their partial financial support of this work. In addition, the authors want to thank the Universidad de Sevilla for the use of experimental facilitates at CITIUS Microscopy and X-Ray Laboratory Services (VI PPIT-2018-I.5 EVA MARÍA PÉREZ SORIANO).
