**3.5 Vickers microhardness and FWHM<sup>−</sup><sup>1</sup>**

Vickers microhardness results are shown in **Figure 8a**. The lowest value of Vickers microhardness corresponds to the SHT sample and the highest value to the P500 sample. Due to recrystallization and precipitation phenomena, as the PHT temperature increased, the Vickers microhardness decreased. The precipitation had a little effect from 300 to 400°C. However, the P500 sample reached the highest Vickers microhardness value at 500°C. In P600 y P700 samples, the PHT temperature increased, and the microhardness decreased due to over aging.

In **Figure 8b** is shown that the FWHM<sup>−</sup><sup>1</sup> increased as the PHT temperature increased. As the Vickers microhardness decreased, the crystallinity quality increased. The lowest FWHM<sup>−</sup><sup>1</sup> value was at 400°C, and then, it trended to increase as the PHT temperature increased. The crystalline quality improved as the PHT temperature increased. In spite of the highest Vickers microhardness value being reached at 500°C (P500), higher temperatures caused that the Vickers

**Figure 7.** *Thermal properties of Kunial brass samples studied, (a) heat capacity and (b) diffusivity (κ) and conductivity (*α*).*

**Figure 8.** *(a) Vickers microhardness and (b) FWHM<sup>−</sup><sup>1</sup> of brass samples with different thermal properties.*

microhardness trended to decrease. A result of a diffusive process at 600°C was observed due to the slow cooling temperature. These diffusive processes produced a recrystallization, improving the crystalline quality.

**69**

**Figure 9.**

*Photothermal images experimental of brass samples, (a) amplitude and (b) phase.*

*Analysis of the Absorption Phenomenon through the Use of Finite Element Method*

In **Figure 9** PTR images are shown. In **Figure 9a**, it is shown that the amplitude increased as the PHT temperature increased until the highest signal of 500°C. Subsequently, amplitude signals decreased as the temperature increased until the lowest value of 700°C. However, no large phase signal changes were

The highest Vickers microhardness and the optimum precipitation were presented in the P500 sample. The lowest Vickers microhardness was obtained in the P700 sample. The comparison among the Vickers microhardness and PTR amplitude and phase signals is shown in **Figure 10**. Vickers microhardness trend is shown in **Figure 10a**. **Figure 10b** illustrates the amplitude behavior was similar to the hardness pattern, because the PTR signal was related to brass structural changes. The maximum PTR amplitude signal was reached at 500°C that is the optimum PHT temperature which corresponded to the maximum Vickers microhardness of the studied brass [25]. It is possible to observe in **Figure 10c**, that the phase signal

*DOI: http://dx.doi.org/10.5772/intechopen.86924*

**3.6 PTR images**

observed in **Figure 9b**.

*Analysis of the Absorption Phenomenon through the Use of Finite Element Method DOI: http://dx.doi.org/10.5772/intechopen.86924*

### **3.6 PTR images**

*Modern Spectroscopic Techniques and Applications*

**68**

**Figure 8.**

**Figure 7.**

*(a) Vickers microhardness and (b) FWHM<sup>−</sup><sup>1</sup>*

recrystallization, improving the crystalline quality.

 *of brass samples with different thermal properties.*

microhardness trended to decrease. A result of a diffusive process at 600°C was observed due to the slow cooling temperature. These diffusive processes produced a

*Thermal properties of Kunial brass samples studied, (a) heat capacity and (b) diffusivity (κ) and conductivity (*α*).*

In **Figure 9** PTR images are shown. In **Figure 9a**, it is shown that the amplitude increased as the PHT temperature increased until the highest signal of 500°C. Subsequently, amplitude signals decreased as the temperature increased until the lowest value of 700°C. However, no large phase signal changes were observed in **Figure 9b**.

The highest Vickers microhardness and the optimum precipitation were presented in the P500 sample. The lowest Vickers microhardness was obtained in the P700 sample. The comparison among the Vickers microhardness and PTR amplitude and phase signals is shown in **Figure 10**. Vickers microhardness trend is shown in **Figure 10a**. **Figure 10b** illustrates the amplitude behavior was similar to the hardness pattern, because the PTR signal was related to brass structural changes. The maximum PTR amplitude signal was reached at 500°C that is the optimum PHT temperature which corresponded to the maximum Vickers microhardness of the studied brass [25]. It is possible to observe in **Figure 10c**, that the phase signal

**Figure 9.** *Photothermal images experimental of brass samples, (a) amplitude and (b) phase.*

behavior did not show large changes as in the amplitude signal. The highest PTR phase signal corresponded to the SHT sample, while the lowest PTR phase signal corresponded at 700°C. This means that the PTR amplitude signal was more sensitive than the PTR phase signal, to observe the effect of the PHT temperature on α brass thermal, structural, and Vickers microhardness properties.
