The problem of using alpha texture

in this picture,the orange part is a model and the white is another model.The orange part use material that include alphaMap,but when i set a alphaMap for the white part ,it looks like lost,like this:

What exactly do you expect to see when you do this?

It looks to me that the white part is blending with the orange behind it in the second picture, which is what you would expect a partially transparent object to do.

like this:

it’s three model that the white model is behind the orange,and the other one behind the white.i set a alphaMap for orange inorder to see the whitle,and set a alphaMap for white inorder to see the model behind white.but when i set a alphaMap for the white,the white model disappear and the third model behind the orange