Annealing Gadolinium 1

[seanof1]

I am having to anneal Gadolinium (oxide and carbide mix) to a temp of 880c and i have a small portion of copper powder mixed in less than 3%. I have knoticed that when I anneal this mixture for 30min at that temp, all my mixture is grey in color and still in powder form. Yet when I take the proccess to one hour the entire powder has turned green in color and has formed into a semi-solid state. I can easly grind the material back down into a powder. Can anyone help me understand what is happaning and why the entire anealling material is turning a dark green when baked for one hour?

I can understand copper turning green; but why the entire batch is a uniform green through out the brick (no grey color present at all) since copper powder is comprising only 3% of the total mass. Am I changing the crystal structure enough at that low a temp for Gd? Could I be forming a metal-alloy with Gd and Cu?

If anyone can help that will be great.

 

[Maui]

You are either oxidizing the copper that is present or more likely forming a new alloy by exceeding the solidus temperature for this alloy composition. For a 3% Cu alloy of Gd the solidus temperature is 860C. Due to the rather poor thermal conductivity of the powder mixture, it may take a certain amount of time for the alloy to actually reach the solidus temperature.

http://www.EngineeringMetallurgy.com

 

[seanof1]

Would 860C also apply to Lutetium?

 

[blacksmith37]

Copper oxides are red and black ( +1 and +2 , as I remember). Green colors are various copper hydroxides, carbonates, S compounds, etc.
Beach sand is typically silica (white), but is turned "sand" color by a couple % iron oxide.