Mg in aluminium alloy reduce weattabilty. Add Mg in such an amount, which does not affect the matrix properties. 

It seems to me that the answer about Mg is wrong..., more likely the correct answer is Ti... So try to use Ti or Zr...

You can fire powder at high temperatures to form oxide layer around particles.

Or you can try electroless metal (Cu or Ni) plating.

you can improve the wet ability by preheating the boron carbide before mixing with the molten Al. If possible reduce the particle size of boron carbide and preheat, surely you get good result.

plz. see the following paper

MECHANICAL AND STRUCTURAL BEHAVIOR OF ALUMINUM

MATRIX COMPOSITE REINFORCED BY B4C UNDER

DIFFERENT PROCESSING TEMPERATURE AND VOLUME

FRACTION OF REINFORCEMENT

K. Shirvani Moghaddama, H. Abdizadehb*, and H.R. Baharvandic

aM.Sc. Islamic Azad University of South Tehran, Tehran, Iran

bSchool of Metallurgy and Materials Engineering-University of Tehran, Tehran, Iran

c Malek Ashtar University of Technology, Tehran, Iran

*[email protected]

would you please illustrate your problem clearly? is it related in wetability of particles or about the distribution of them due to the stirring process??? you may send me your question directly via [email protected] 

I really appreciate your valuable comments, here are some extra notes:

Adding Mg will improve the wettability by enhancing some reactions at interface; however, Mg oxidation even in presence of Ar gas makes it difficult to add powder through vortex. I know powder oxidation and pre-heating can be helpful, however, I’m not sure about tools and facilities. I mean, practically, temperature of the powder (~773 K) will be suddenly reduced as we bring it out of furnace.

Sodium has a dramatic influence on surface tension of Alumnium. Only few ppm Sodium in the surface area decrease surface tension of Al. Way to bring in Sodium could be over NaOH or NaCl (depending on wht is requirement ofr final material). NaOH interacts with Al melt boilding some Al oxide and Na.

To check is the impact of final metrial properties, usually Sodium based impurities are not desired.

Please refer our following publication 

1. V. Auradi*, Rajesh G. L & S. A. Kori, Preparation and Evaluation of Mechanical Properties of 6061Al- B4Cp Composites Produced via Two-Stage Melt Stirring, Materials and Manufacturing Processes, Taylor and Francis, DOI:10.1080/10426914.2014.892617.

If you do not like to add any new elements, simply increase the superheat of the liquid and keep stirring the melt.

Increase in the temperature will increase the wettability (decrease the contact angle).

Check this paper:

http://www.sciencedirect.com/science/article/pii/S0167577X07008087

Use pottasium hexa flouro titanate (K2TiF6)

1-2 % by weight addition of Mg can improve the wettability

Do mention your Base alloy. Try for two step stir casting i.e. adding the reinforcement just below the melt temperature of aluminium (Semi solid melt) stir for effective time and then continue to increase the melt temperature with stirring.

The problem with the wettability of aluminium is the formation of the oxide layer. The hexaflurotitanates of potassium and sodium used as a flux will dissolve the oxide but will still protect aluminium from oxidation. The risk of doing this is that there is danger of aluminium reacting with B4C.

(1) Preheat the particles

(2) Adding wettability agents such as K2TiF6 

(3) Adding the particles within the freezing range of the aluminum alloy (Known as compocasting or slurry casting)

(4) Coat the particles with some metallic elements having higher melting point