Restoring Ductility to Zamak 3? (Zinc-Al alloy)

[metalman8357]

Hi all,

I have parts that were die-cast from Zamak 3. The parts are meant to undergo slight bending and plastic deformation in service. Our new lot, however, undergoes cracking during this process which indicates a decrease in ductility. The chemistry shows that the parts are within the specification, but that the copper content is slightly high at 0.66% and the standard lists a max of 0.1% (the standard also states that a copper content up to 0.7% should not adversely affect mechanical properties, and should not be a basis for rejection). We do not do any mechanical testing on these parts to confirm properties, just the bend test. My question is, we have 5,000 of these parts made and I'm wondering if there is a heat treat process that we can do to restore ductility to these parts.

 

[swall]

The first step would be to penetrant inspect some of the parts prior to the bend test in order to determine if there are pre-existing cracks.

 

[TVP]

The problem is likely due to casting defects such as porosity or cold shuts, misruns, etc. You need to have the parts metallurgically evaluated. There is no heat treating process that will heal these defects.