Alpha is another word that gets used for transparency in graphics

to bring up the material attributes you can either do it from the hypershade
or you can select the object with the material
hold down right click, and let go on "Material Attribute..."

you'll see under Common Material Attributes a value for Transparency (circled in red), just move the slider (circled in green) from one end to the other and just right click on the square (in this screen shot its the black box in the middle of my coloured circles) and hit Set Key

then just go to another frame, and do the same


of course, using this method means you will see the entire object appear all at once.
it wasn't too clear from your original post if this was what you were after or not