I want to know that i can do heat treatment Al2O3 particles ( 900 deg for 2 hrs ) without inert gas ?
because i don't have this instruments for inert gas in the furnace.
hell Esmaeil, definitely not. The alumina is already oxidized so you can heat treat the powder in hot air. Use the powder immediately after that or put it into a closed container to avoid takeup of water from ambient air.
Hi Esmaeil, since my last answers I get some new info about your process. Alumina is heated with Al metal in argon atmosphere, but degassing is really slow process so it is better (if controlled atmosphere in furnance is not available) place hot alumina in argon (dessicator, box or basin) for cooling. Melting of alloy + alumina should be in argon before reduction with Mg (it was oxidized by Al2O3 to MgO), and MgO build on alumina surface spinel layer MgAl2O4 (slowly begun from 850oC but better at 950-1030oC) wich is wetted by Al in presence of magnesium nitride. To have magnesium nitride in alloy, argon should changed after spinel formation on nitrogen.
Boron activation is also suitable for Mg-containing Al-alloys ( maybe for A356) . In old US patent it is described as ammomium borate solution pretreatment and calcination (~1100oC). Elemental boron is also effective (0.1%) but I dont know cost effective sources of elemental boron ( ferroboron is cheap but Fe impurities lead to crisp alloy)
Addition of 1% hafnium to Al led to same strength as for best composites with Al2O3 nanopowders, but current Hf price is 1000000$/tonne :-)
Mg and N would help wettability if at least 900C is reached, moisture in Al2O3 should be taken out of Al2O3 by this heating process...previous drying might not be needed...
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