How calcium prevents precipitation hardening in Al–Mg–Si alloys
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OriginalversjonMaterials Science & Engineering: A. 2013, 575 241-247. 10.1016/j.msea.2013.03.067
We have investigated the effect on precipitate microstructure and hardness upon adding small amounts of Ca to a base Al–Mg–Si alloy. The main investigative techniques were transmission and scanning electron microscopy. We found that large Ca-containing particles with composition CaAl2Si2 form during the production stages of the alloy. The particles leave less Si available in solid solution for the nucleation of hardening precipitates, leading to a coarser microstructure consisting of less coherent precipitates. The resulting hardness decrease is measurable for alloys containing more than 60 at ppm of Ca.