Micro cracks appear in ALSi10Mg alloy castings

[jessieleo99]

Hello everyone,

I am currently working on a production project for aluminum alloy castings and have encountered some challenges. We are using the ALSi10Mg alloy, however, during the cooling stage, microcracks have appeared.

Here is the relevant data:
Alloy composition: Si 10%, Mg 0.3%, Cu 0.05%, Fe 0.2%, Zn 0.1%, Ni 0.05%, and the remainder is Al.
Casting dimensions: Length 120 mm, width 80 mm, thickness 15 mm, produced using sand casting.
Crack location: Mostly concentrated on the outer surface of the casting and some areas inside the cavity.
Cooling conditions: Natural cooling.

We have already taken the following steps:
①solution treatment (500°C for 2 hours) + aging treatment (160°C for 6 hours).
②performed acid pickling on the casting surface to remove potential oxides.
However, the cracking issue persists, especially on the outer surface of the castings. Does anyone have any suggestions for this issue?

 

[mfgenggear]

OP
The rapid uneven cooling of thick and thin sections, and complex geometry
With cause induced stresses,
Because the thin sections with cool faster than the thick sections.
It may or may not work but a stress relieve after casting. To stabilize and slowly cool and normalize the parts.
I would suggest to immediately soak in an oven.

 

[swall]

How were the cracks discovered? Visual examination? Penetrant inspection?