Hello,
I need help. When taking a sample during the casting process for chemical analysis of aluminum alloy 6082 with a Si content of 1.20 - 1.30, I took four consecutive samples.
I did four emission spectroscopies on each sample. The Si content is quite unstable already on the same sample.
1. sample: 1.2905; 1.2934; 1.2491; 1.2268
2. sample: 1.2417; 1.2844; 1.2908; 1.2413
3. sample: 1.2602; 1.2401; 1.2180; 1.2433
4. sample: 1.3787; 1.3532; 1.3297; 1.3438
In the same charge, I cut the sample on an extrudet rod and the Si value was much higher than on the chemical samples taken during casting. (1.32).
The emission spectrometer is calibrated daily!
Does anyone have any solution?
Thanks
When the rod crystallizes from the Al-Si melt, a silicon concentration gradient is naturally formed with a maximum located on the rod axis. This is because compositions with a higher silicon content have a lower melting point. So, it is not surprising that in different places of the cross-section of the cast rod you measure different concentrations of silicon, this is how it should be.
This is quite normal! Si content in the Al cast parts usually is not homogenous. Parameters like the temperature gradient of the mold and holding time in the molten state would highly affect the distribution. I would advise reporting an average value.
Dear Robert
Distribution of Si is not homogeneous in the Al matrix and depends on some experimental parameters. So, as Mehdi Akbarifar and Vadim Verlotski have said, it expects that different places don't have the same value of Si content.
to ensure, please see the distribution of Si phase in the microstructure of the 6082 Al alloy.
However, the sample 1 to sample 3, show almost same content of Si. Average value has been recommended to report.
Also to complete Esmaeil a standard deviation it would help you to highlight even more the results obtained.
