PSI - Issue 23

Petr Haušild et al. / Procedia Structural Integrity 23 (2019) 179–184 Haušild et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 2. Nanohardness of mechanically alloyed powders prepared from different feedstock as a function of milling time.

The evolution of nanohardness after milling is show in Fig. 2. The powders prepared form pure elements (Fe_Al_Si) and pre-alloy AlSi30 (Fe_AlSi) showed an increase in the hardness from the beginning of milling. In the beginning of milling (after 1 h), the particles prepared from pre-alloyed AlSi30 powders showed lower hardness but steeper increase in hardness than the particles prepared from elemental powders, which was probably caused by faster creation of (softer) Al-Si lamellae. However, the hardness became equal for batches from elemental and pre-alloyed AlSi30 powders after 2 h, and the plateau of stabilized hardness was rapidly reached (practically no changes in the hardness occurred in these batches after milling times ≥ 4 h). On the other hand, the powders prepared from initially already hard pre-alloyed FeAl (FeAl_Si) and FeSi (FeSi_Al) feedstock showed firstly a dwell (FeAl_Si) or even decrease of hardness (FeSi_Al). After that the hardness increased up to 8 h when the plateau of stabilized hardness was reached.