PSI - Issue 23

Jan Pinc et al. / Procedia Structural Integrity 23 (2019) 21–26 Jan Pinc et al./ Structural Integrity Procedia 00 (2019) 000 – 000

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2.3. Hardness of prepared materials

It was found by the micro-hardness measurements that the hardness of those particular phases (zinc dendrites, eutectic mixture and CaZn 13 ) did not change in relation to the cooling rate. It can be seen in Fig. 4 that the micro hardness on the edge (OUT) of a sample and in the core of a sample (IN) was within the error range the same. The average hardness of the particular phases is shown in Table 2.

Table 2. Single phases micro-hardness. Phase

HV0.01

Zn

60

Mg 2 Zn 11

135 223

CaZn 13

250

50mm IN

200

50mm OUT

150

100 HV0.01

50

0

Zn dendrites eutectic system CaZn13

Fig. 4 Micro-hardness of the particular phases in the core and on the edge of the ingot with a diameter of 50 mm.

Macro-hardness of the materials with different diameters is shown in Fig. 5. The slight decrease of hardness can be explained by the gradual increase of the size of zinc dendrites. In case of the annealed sample, the hardness increased approximately 20 HV compared to the as-cast ingot. This increase is connected with the more homogeneous distribution of Mg 2 Zn 11 and its transformation from the lamellar structure to compact phase without the zinc present.

0 20 40 60 80 100

HV30

87,6

81,3

77,8

F5

F30

F50

Fig. 5 Hardness (HV30) of the as-cast materials with a diameter of 5 mm (F5), 30 mm (F30) and 50 mm (F50).