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Diffnt suppliers, same composition (AlTiB) yielding 2 different Grains

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selseg
#1
Feb18-13, 05:47 AM
P: 27
I work at an Aluminum sheet casting plant, we use AlTiB as the grain refiner for our cast products.Ti:B ratio as indicated on certificates is 5:1 .We recently received a new consignment of AlTiB from another supplier in India.The certificates from our new supplier show that the The AlTiB we bought is of the same composition as the old one.However the new one doesn't yield good grains even when the rod is fed into the molten metal at faster rates.I decided to melt samples of the two Grain Refiners and determine their compositions with AAS.I made the following observations the two samples had the same composition.Interestingly the Ti: B Ratio was 20:1.Ti composition was about 10% whiles that of Boron was about 0.5%The only noticeable physical difference between the two refiner rods is the lustre, the new rod has a dull surface appearance.

QUESTION 1 : Both samples have the same composition , why don't I get good grains with new sample ?
Is there any other factor that influences AlTiB refiner properties aside composition ?

QUESTION 2 : How come Ti:B ratio for both samples(as determined by me after melting and analysing) is 20:1 rather that 5:1 as indicated on the product certificate.
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Alkim
#2
Feb18-13, 02:39 PM
P: 98
The answer to your first question is that the reason could be either impurities, or grain size, although the latter may not be valid if you fuse completely the material.
As to the second question, provider's specifications are probably in mol % and your analysisi is in wt%. The molar mass of Ti is roughly 4 times larger than that of B.
selseg
#3
Feb19-13, 04:15 AM
P: 27
Thank you very much Alkim ,It makes a lot of sense. But still on the first question , below are the results from the two samples .less than 0.3% of the composition is not accounted for from the analysis .Is that enough impurity to make such a huge difference ?

Al --88.441 --89.443
Si --0.1040 --0.099
Fe --0.2160 --0.185
Cu --0.0122 --0.0099
Mn --0.0070 --0.005
Mg --0.0005 --0.0005
Cr --0.0026 --0.002
Zn --0.0020 --0.0036
Ti --10.345 --9.5798
Ni --0.0173 --0.0116
Pb --0.0170 --0.015
V --0.0636 --0.0084
B --0.5331 --0.419
SUM --99.762 --99.782

Alkim
#4
Feb19-13, 11:57 AM
P: 98
Diffnt suppliers, same composition (AlTiB) yielding 2 different Grains

It is hard to answer whether those 0.3 % are important or not without having any additional information about your system, concentrations, applikcation, etc. Depending on that, 0.3 % could be considered a huge amount or just insignificant traces. What's more, the problem could be even in the apparently small differences in the analysis of the two materials. If you are sure the problem is in the new material you can just reject it as a row material. However, if you do need to clarify the real cause for the difference and you can allow it I recommend you to consider obtaining expert help from a university or a technological center.
selseg
#5
Feb19-13, 12:02 PM
P: 27
Thank you very much Alkim ,I will do just that
Alkim
#6
Feb19-13, 12:34 PM
P: 98
You are wellcome. By the way, I have just found this article. A quick look at it has made me think that probably it is a matter of granulometric distributuion. Try to have a look at both materials using a microscope (after etching the samples with an acid if necessary). The difference in their lusters might be an indication of different particle sizes.

Regards


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