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小木虫(金币+0.5):给个红包，谢谢回帖交流
It is not always that Sb significantly modifies the morphology of Mg2Si in Mg alloys, for example, it has been reported that Sb has very limited modification effect on AZ61-0.7Si alloy. The Chinese script Mg2Si phase is also controlled by solidification rate, such that Mg2Si may always be Chinese script type if the solidification rate is too low. Therefore, it may be normal that you do not observe modification effect on your Mg-12Al-0.7Si-0.3Sb. Nevertheless, you may check if you have done the following items correctly:
(1) Are your starting materials OK? Magnesium, Al and Sb should be at least 99.9%, Si should be added through Al-Si master alloy (for exp., Al-30%Si) rather than Si.
(2) Is 0.3% Sb a good level for your specific alloy? Maybe 0.15, 0.45 and 0.6% should be tried.
(3) Is your casting condition correct? A typical casting process for Mg alloys consists of
- Melting Mg in graphite crucible at T = 720-750C with flux protection
- Adding alloying elements (Al, Sb and Al-Si master alloy in your case)
- Keeping the molten metal at T = 720-750C for 15-60 min
- Stirring the molten metal for 2 min with stainless steel rod
- Keeping the molten metal at T = 720-750C for 10-15 min to settle down oxidation and other contaminations
- Pouring the molten metal through ceramic foam filter (if you have) with SF6 gas protection
- Pouring the molten metal into pre-heated (150-200C) steel mould
If you really cannot see modification effect, maybe you have to change 0.3%Sb to other concentrations, or, maybe Sb has no effect on Mg-12Al-0.7Si at all, then you have to try something else, such as Sr.
Hopefully some of the above information is useful to you.
[ Last edited by 金教授 on 2010-11-8 at 16:57 ] |
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