Heat treatment of Al 771.0 T71

[Nadimuthu]

We have used 771.0 al alloy for the first time for our sand casting process.While subjecting the castings to T71 process we have observed that the hardness achieved was only 65 BHN as against 120 specified.The alloy has been checked for chem composition from the casting cut-portion and found to be within limits.
The recommended T71 treatment is 580 to 595C for 6 hours,cool outside furnace to still air and age by holding at 140C for 15 hours.Similar properties can be obtained by aging at 155c for 3 hours.We have tried in both methods but the hardness is only within the 60-65 BHN range.
The major alloying elements are Zn 6.5 to 7.5,Mg 0.8 to1.0%,
Cr0.06 to 0.2%.
Please give us your suggestions.

 

[jrunkle]

I have a similar problem....

 

[Nadimuthu]

Dear jrunkle,
Could you please share some more details of your experiments so that we can jointly try to find a solution.

 

[jrunkle]

Unfortunately this problem involves a legal issue, so I cannot discuss it in a public forum. If possible contact me directly at jrunkle@ultraclad.com or call me at 978-470-1620.