Influence of the Shaping Microstructure Technology and Properties of AlMgSi Alloys on Microcracks Formation under an Influence of Static Compression Loads

Endeavours were undertaken to assess metallographically AlMgSi alloys, (containing 0.58 wt% of Mg, and 0.58 wt% or 6.5 wt% of Si) in their primary states as well as after applying external loads in the Static Compression Test. During the first stage of the study the primary microstructures of the investigated samples were assessed. Samples originated from two technological processes: after strain hardening, in a form of rods (φ 9.5 mm and φ 4.0 mm) gravity casting, rolling, homogenisation and precipitation hardening; and after gravity casting in sand moulds of shaped plates 100 mm x 100 mm x 4 mm of a primary structure and after the precipitation hardening. During the second stage of investigations, microstructures of analysed samples (of various technological history) were compared - after applied external loads - in order to obtain information in what way such diversified primary structure and which of its stereological parameters (amount, shape, size and placement) are essential in initiation of microcracks under static loads.