Strontium For Aluminum-Silicon alloy modification

[MetalEng]

I used Sr-treating for modification of A356 Al alloy .
But after tensil test, I got abnormally low ductilities
%Elongation) I blame the Strontium quality. Could you please let me know your opinions at this regard? as well, your comments about storing standard reference for strontium and some applied tips for modification aided strontium are welcome.
Thanks all.

 

[etch]

Hello

Its been a while since i used strontium, but il try and help out.

You never said in what form you used strontium, i take it it was in rod or some other al:sr mix. Storage is never usually a problem in this form. I would say that you have either got one or two problems.

1) The wrong concentration of Sr was provided, either in tablet form or rod.
2) I have found that Sr fades out, not as bad as sodium but needs stirred occasionally to keep activated. If the pot was left for a long peroid before casting ti may be this.
3) Sr tends to introduce more porosity to castings, although more disperesed, it could be your test piece was filled with porosity.

I sugest finding the following, was the results significantly lower, ie lower than that of the unmodified alloy, this would tend to suggest that porosity was the casue. Have you examined the test piece?

Are you sure the alloy composition of the pot was correct prior to the addition of Sr. I rmember once i recieved a sample and the company was adamant that it was correct oonly to find out that the material had 10% Zinc, instead of 0.5%.

 

[swall]

MetalEng--I ran across an item on Sr modification today while looking up something else. Basically, as the iron content in Sr modified alloys increases, the tensile strength decreases. But, you didn't mention anything about the tensile being low, only elongation?

 

[MetalEng]

Dear etch & swall,
Both, Thanks a lot. Operator mistake was caused this problem. Is it possible I refer you for next probable probleme?