**3. Mechanical tests**

#### **3.1 Impact fracture tests**

The impact fracture tests were performed using a Charpy pendulum, to measure the energy absorbed in the process of dynamic fracture of standardized (notched)

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**Figure 4.**

*Characterization and Testing of High-Entropy Alloys from AlCrFeCoNi System for Military…*

specimens. The values resulting from the impact fracture test for some AlCrFeCoNi

As can be seen from the values of the breaking energy shown in the table, the experimental materials have a tenacity corresponding to structural steels, while the

The hardness of the experimental materials was determined using the Shimadzu HMV2T microhardness apparatus in Lamet Laboratories from *Politehnica* University of Bucharest. The measurements were made in line, with mark distances of about 500 μm, using the fingerprint force of 0.1 N and pressing time of 10 seconds [9–12]. For the AlxCryFezCovNiw system, the entire spectrum of microhardness values in the

x = y = z = v = w = 0.2 … 2 at% range was analyzed, as shown in **Figure 4**.

The coding of the samples in **Figure 4** was based on the atomic proportions of the chemical elements; thus, HEA 1 = AlCrFeCoNi; HEA 2 = Al1.5CrFeCoNi; HEA 3 = Al2CrFeCoNi; HEA 5 = Al0.8CrFeCoNi; HEA 6 = Al0.6CrFeCoNi; HEA 7 = Al0.4CrFeCoNi; HEA 8 = Al0.2CrFeCoNi; HEA 9 = Al1.2CrFeCoNi; and HEA 10 = Al1.4CrFeCoNi. The maximum hardness value was obtained for the sample

The coding of the samples in **Figure 5** was based on the atomic proportions of the chemical elements; thus, HEA 11 = AlCrFeCoNi1.2; HEA 12 = AlCrFeCoNi1.4; HEA 13 = AlCrFeCoNi1.6; HEA 14 = AlCrFeCoNi1.8; HEA 15 = AlCrFeCoNi2; HEA 16 = AlCrFeCoNi0.8; HEA 17 = AlCrFeCoNi0.6; HEA 18 = AlCrFeCoNi0.4; and HEA 19 = AlCrFeCoNi0.2. The maximum hardness value was obtained for the sample

 62.1 67.1 67.0 66.0 62.4 62.7 67.2 66.9 65.8 62.3 62.1 67.0 67.1 65.9 62.1 62.2 67.3 68.9 66.1 62.1

**HEA 1 HEA 5 HEA 6 HEA 12 HEA 14**

*DOI: http://dx.doi.org/10.5772/intechopen.88622*

hardness values are similar to those of tool steels.

HEA 3, with maximum concentration of aluminum.

**Test no. Impact energy, J**

*Impact fracture energy values for some experimental HEAs.*

*Microhardness HV0.1 values for experimental HEA 1 to HEA 10.*

alloys are shown in **Table 2**.

**3.2 Microhardness**

HEA 11.

**Table 2.**

*Characterization and Testing of High-Entropy Alloys from AlCrFeCoNi System for Military… DOI: http://dx.doi.org/10.5772/intechopen.88622*

specimens. The values resulting from the impact fracture test for some AlCrFeCoNi alloys are shown in **Table 2**.

As can be seen from the values of the breaking energy shown in the table, the experimental materials have a tenacity corresponding to structural steels, while the hardness values are similar to those of tool steels.

#### **3.2 Microhardness**

*Engineering Steels and High Entropy-Alloys*

of approx. 1.6855 kg per ingot.

*remelting procedure in VAR equipment.*

**3. Mechanical tests**

**3.1 Impact fracture tests**

alloy plates obtained by casting are shown in **Figure 3**.

related network was 1.111 and 0.574 kg, respectively, resulting in an alloy quantity

*HEA Al0.8CrFeCoNi alloy plates obtained by VIM-VAR technology. (a) As-cast HEA samples obtained by VIM technology; (b) HEA sample positioned in copper plate of VAR equipment to be remelted; (c) sample after* 

The quantities of materials used for each batch, also taking into account the oxidation losses, are as follows: Al = 0.74 kg; Cr = 1.70 kg; Fe = 1.85 kg; Co = 1.95 kg; and Ni = 1.93 kg. The total weight of the batch was of 8.17 kg. The Al0.8CrFeCoNi

The production of the HEA Al0.8CrFeCoNi plates was completed by refining in the vacuum arc remelting furnace, for which, based on the requirements of the

The working procedure in the VAR furnace was classical, seeking the most efficient homogenization of the alloy to ensure the best possible mechanical properties,

The impact fracture tests were performed using a Charpy pendulum, to measure the energy absorbed in the process of dynamic fracture of standardized (notched)

military field, a special copper plate was made, according to **Figure 2b**.

by remelting each sample three times on each side (**Figure 3c**).

Since alloy losses occur due to oxidation, due to the interaction with the furnace walls and to the casting ladle, a quantity of 8 kg of prepared alloy is considered per

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batch.

**Figure 3.**

The hardness of the experimental materials was determined using the Shimadzu HMV2T microhardness apparatus in Lamet Laboratories from *Politehnica* University of Bucharest. The measurements were made in line, with mark distances of about 500 μm, using the fingerprint force of 0.1 N and pressing time of 10 seconds [9–12]. For the AlxCryFezCovNiw system, the entire spectrum of microhardness values in the x = y = z = v = w = 0.2 … 2 at% range was analyzed, as shown in **Figure 4**.

The coding of the samples in **Figure 4** was based on the atomic proportions of the chemical elements; thus, HEA 1 = AlCrFeCoNi; HEA 2 = Al1.5CrFeCoNi; HEA 3 = Al2CrFeCoNi; HEA 5 = Al0.8CrFeCoNi; HEA 6 = Al0.6CrFeCoNi; HEA 7 = Al0.4CrFeCoNi; HEA 8 = Al0.2CrFeCoNi; HEA 9 = Al1.2CrFeCoNi; and HEA 10 = Al1.4CrFeCoNi. The maximum hardness value was obtained for the sample HEA 3, with maximum concentration of aluminum.

The coding of the samples in **Figure 5** was based on the atomic proportions of the chemical elements; thus, HEA 11 = AlCrFeCoNi1.2; HEA 12 = AlCrFeCoNi1.4; HEA 13 = AlCrFeCoNi1.6; HEA 14 = AlCrFeCoNi1.8; HEA 15 = AlCrFeCoNi2; HEA 16 = AlCrFeCoNi0.8; HEA 17 = AlCrFeCoNi0.6; HEA 18 = AlCrFeCoNi0.4; and HEA 19 = AlCrFeCoNi0.2. The maximum hardness value was obtained for the sample HEA 11.


#### **Table 2.**

*Impact fracture energy values for some experimental HEAs.*

**Figure 4.**

*Microhardness HV0.1 values for experimental HEA 1 to HEA 10.*

The coding of the samples in **Figure 6** was based on the atomic proportions of the chemical elements; thus, HEA 20 = AlCrFeCo0.8Ni; HEA 21 = AlCrFeCo0.6Ni; HEA 22 = AlCrFeCo0.4Ni; HEA 23 = AlCrFeCo0.2Ni; HEA 24 = AlCrFeCo1.2Ni; HEA 25 = AlCrFeCo1.4Ni; HEA 26 = AlCrFeCo1.6Ni; HEA 27 = AlCrFeCo1.8Ni; and HEA 28 = AlCrFeCo2Ni. The maximum hardness value was obtained for the sample HEA 26.

The coding of the samples in **Figure 7** was based on the atomic proportions of the chemical elements; thus, HEA 29 = AlCr0.2FeCoNi; HEA

**Figure 5.**

**Figure 6.**

*Microhardness HV0.1 values for experimental HEA 20 to HEA 28.*

**147**

**Figure 9.**

*Experimental as-cast AlxCrFeCoNi alloys.*

*Characterization and Testing of High-Entropy Alloys from AlCrFeCoNi System for Military…*

*DOI: http://dx.doi.org/10.5772/intechopen.88622*

*Microhardness HV0.1 values for experimental HEA 38 to HEA 46.*

**Figure 8.**

**Figure 7.** *Microhardness HV0.1 values for experimental HEA 29 to HEA 37.*

*Characterization and Testing of High-Entropy Alloys from AlCrFeCoNi System for Military… DOI: http://dx.doi.org/10.5772/intechopen.88622*

**Figure 8.**

*Engineering Steels and High Entropy-Alloys*

HEA 26.

The coding of the samples in **Figure 6** was based on the atomic proportions of the chemical elements; thus, HEA 20 = AlCrFeCo0.8Ni; HEA 21 = AlCrFeCo0.6Ni; HEA 22 = AlCrFeCo0.4Ni; HEA 23 = AlCrFeCo0.2Ni; HEA 24 = AlCrFeCo1.2Ni; HEA 25 = AlCrFeCo1.4Ni; HEA 26 = AlCrFeCo1.6Ni; HEA 27 = AlCrFeCo1.8Ni; and HEA 28 = AlCrFeCo2Ni. The maximum hardness value was obtained for the sample

The coding of the samples in **Figure 7** was based on the atomic proportions

of the chemical elements; thus, HEA 29 = AlCr0.2FeCoNi; HEA

**146**

**Figure 7.**

**Figure 6.**

**Figure 5.**

*Microhardness HV0.1 values for experimental HEA 20 to HEA 28.*

*Microhardness HV0.1 values for experimental HEA 11 to HEA 19.*

*Microhardness HV0.1 values for experimental HEA 29 to HEA 37.*

*Microhardness HV0.1 values for experimental HEA 38 to HEA 46.*

**Figure 9.** *Experimental as-cast AlxCrFeCoNi alloys.*

30 = AlCr0.4FeCoNi; HEA 31 = AlCr0.6FeCoNi; HEA 32 = AlCr0.8FeCoNi; HEA 33 = AlCr1.2FeCoNi; HEA 34 = AlCr1.4FeCoNi; HEA 35 = AlCr1.6FeCoNi; HEA 36 = AlCr1.8FeCoNi; and HEA 37 = AlCr2FeCoNi. The maximum hardness value was obtained for the sample HEA 36.

The coding of the samples in **Figure 8** was based on the atomic proportions of the chemical elements; thus, HEA 38 = AlCrFe0.2CoNi; HEA 39 = AlCrFe0.4CoNi; HEA 40 = AlCrFe0.6CoNi; HEA 41 = AlCrFe0.8CoNi; HEA 42 = AlCrFe1.2CoNi; HEA 43 = AlCrFe1.4CoNi; HEA 44 = AlCrFe1.6CoNi; HEA 45 = AlCrFe1.8CoNi; and HEA 46 = AlCrFe2CoNi. The maximum hardness value was obtained for the sample HEA 38, for minimum concentration of iron.
