Zinc melting problem

[natanrajch]

Hello,
Ive been trying to make a small Zn/Al disc. So, I started with some Zn tablets and a little piece of Aluminum cable (3% wt or so), and put them in a graphite crucible (fully covered), then heated it in an oven to 800ºC and waited for an hour.

After that, all I get is a poor sintered of the zinc tablets. And one time Ive got nothing but a soft white appearence (oxide i guess)

The melting point of the Zinc is 420ºC, and the aluminum has it at 660ºC. Im working with just a few grams of material

Should I wait more time? should i heat it more? Is there any evident fact im missing here?

THANKS!

[DMF_TomB]

if you melt zinc high enough temperature it will vaporize.
.
many metals like aluminum bronze iron alloy. the copper and iron are dissolved at far lower temperatures than their regular melting point. i have added 1/8" diameter rod by holding it in the molten metal and slowly it will dissolve the end in contact with molten metal.. or take thin wire and roll in up and submerge it in the molten metal.
.
often it is easier to just buy zinc aluminum alloy already made up in ingots. often melting scrap you will pick up porosity from hydrogen from water, fuel, combustion gases that are difficult to remove unless you have chlorine bubbler or degassing setup.
.
try
Foundry Casting Metals
for zinc aluminum ingots in small quanties

[natanrajch]

Thanks DMF!

I had already bought some Zamac (that is, the commercial alloy) and it melted perfectly.
The thing now is that I wanted to obtain a disc with less Aluminum (Maybe 1% wt.), and to avoid the magnesium impurity. This is why im struggling with metallic Zinc and Al.

The oven I use is electric, so there wont be any problem with fuel gases. It seems there is some kind of a problem with me instead... you know, I thought "Get it to the melting point... and it will melt"

Do you recommend me melting the Zinc first and then adding the Aluminum?
Is it better to mantain the crucible covered or itll be the same?

thanks in advance

[Dennis H]

At 703 degrees C the zinc will oxidize. Put both the zinc and the AL in the crucible. cook it at 621 C. When the zinc melts it will start to "digest" the AL. If possible stir it the AL will go in. It just takes a little while.