The aluminum/alumina couple has inherently a wetting angle of roughly 110° i.e. it is non-wetting. Additions of Mg (yet at a higher level than in the A356) are known to reduce the wetting angle somewhat, yet not to the point where a particle bed would be internally wetted. There is, however, the observation that Al-Mg melt in combination with nitrogen atmosphere can lead to pressureless infiltration (cf. Lanxide process). As to your specific problem, i.e. to mix alumina into semisolid A356, the success will strongly depend on the particle size of alumina that you are using: for large particles (i.e >40 µm), shear forces exerted by stirring may be sufficient to break up the particle clusters (those clusters being the most difficult to wet). This being said, it obviously depends on how vigourously you mix your melt with the powder. Depending on what the further process steps are you may consider producing premixed ingots by pressure assisted infiltration (with relatively high particle contents) which are subsequently diluted in larger quantity of alloy. The reasoning behind being that once a cluster is infiltrated it may much more easily be broken apart.

Hi, since Al2O3 has a smooth and glassy surface therefore reinforcement of this particle is not a simple work, theorectically it need a rough surface to increase the wettability properties maybe you need to find special treatment on this inert and hard surface of Al2O3. Anyone has any idea on this....

Dear Zawati

thanks alot, but can you tell me more about this and anything in your mind

Normally wettability depends on the suface energy of the liquid , solid and the interface . Therefore, It can be impoved by preheating the powders and adding some metallic elements such as Mg, Cu and Ti with the matrix material. Surface coating of the Alumina particle with these mettalic element will workout greatly

Dear S. Balasivanandha Prabu

thanks alot for your answering

it was so complete and comprehensive

The aluminum/alumina couple has inherently a wetting angle of roughly 110° i.e. it is non-wetting. Additions of Mg (yet at a higher level than in the A356) are known to reduce the wetting angle somewhat, yet not to the point where a particle bed would be internally wetted. There is, however, the observation that Al-Mg melt in combination with nitrogen atmosphere can lead to pressureless infiltration (cf. Lanxide process). As to your specific problem, i.e. to mix alumina into semisolid A356, the success will strongly depend on the particle size of alumina that you are using: for large particles (i.e >40 µm), shear forces exerted by stirring may be sufficient to break up the particle clusters (those clusters being the most difficult to wet). This being said, it obviously depends on how vigourously you mix your melt with the powder. Depending on what the further process steps are you may consider producing premixed ingots by pressure assisted infiltration (with relatively high particle contents) which are subsequently diluted in larger quantity of alloy. The reasoning behind being that once a cluster is infiltrated it may much more easily be broken apart.

Dear Ludger

thank you

Dear Esmaeil,

in order to get basic ideas please check our works on novel aluminium brazing technique:

ISBN: 978-3-86359-089-5

Dear Andreas

thanks but can you say about this numbers?

Change the surface tension with a "coupling" agent, perhaps.

Dear Hong Li

thanks alot

can you tell me some references for your topic?

Dear Esmaeil,

several effects can improve the wettability. The mentioned (and related) work shows the influence of thermal effects and pressure, but for bulk Al2O3. However it can give you ideas, in what direction you can think. In general it is worth trying to enhance the high temperature dissolution of Al2O3 in presence of Aluminium.

thanks Andreas

I recommend to read the following article. It's very useful for your work.

Sajjad Amirkhanlou, Behzad Niroumand, Development of Al356-SiCp cast composites by injection of SiCp containing composite powders, Materials and Design 32 (2011) 1895–1902.

Please find the attachment.

Mr.Jamaati

thanks alot

I studied this article in the past.

I am also facing the same problem. Will preheating Al2O3 will solve the problem? If so to what temperature? Can any one suggest please...

or

If Mg is added will it solve the problem?

How much Mg has to be added? Any clue from any one?

dear jayaraman

Hi,

Will preheating Al2O3 will solve the problem? Relatively... in some articles mentioned but in this work, i used Al and Cu powder with Al2O3 ( Ball milled ) that improved wettability of ceramic particles with molten Al... 

If Mg is added will it solve the problem? when we use the Mg powder for enhancing the wettability, we must use the inert atmosphere, but i don't have these instruments.

Two ways to solve the problems. As mentioned by Prof. Ludger Weber and other researchers, Mg addition will certainly will improve the wettability. The same time, preheating Al2O3 will also try to improve the wettability. Preheating the ceramic particles will increase the surface energy of the ceramic particles. It is better to use inert gas during the process to solve this issue