its called billet when it comes from the factory, some people choose to machine the billet into shape, some mold it. not sure why, but the casting process make it weaker than billet thats been machined. at least thats what ive always been told.
maybe some aluminum person will see this and explain for us! lol.. if you break a cast piece and look at the inside it looks grainy? maybe the process that the companies use to cast causes that? i now every hobby ive been into the same logic applies... billet is always better.


here.. maybe this explains it? the process is very strict when it comes out of a factory as billit.

"Alcoa’s billets are produced to provide the best performance at the extrusion press in terms of speeds, surface finish and mechanical properties. Before casting, the molten metal is treated to ensure it is clean and free of excessive hydrogen contamination. Alcoa extrusion ingot is virtually free of dross, porosities, metallic inclusions, oxides or other undesirable contamination and discontinuities. The chemical trace elements are controlled to a very low contamination level. The internal microstructure is modified through a controlled thermal treatment known as homogenizing process. The main objectives for homogenizing the billets are: minimize the detrimental effect of the “as cast” Fe phases, eliminate grain or micro- segregation and break up the intermetallic constituents producing a well refined easier to extrude microstructure."


maybe when a 3rd party casts a piece the process isnt as good?

in that link you provided theres some intersting facts.. but it doesnt answer our question...

cast alloys use a different number system, there will be a decimal point.

The Aluminium Association (AA) has adopted a nomenclature similar to that of wrought alloys. British Standard and DIN have different designations. In the AA system, the second two digits reveal the minimum percentage of aluminium, e.g. 150.x correspond to a minimum of 99.50% aluminium. The digit after the decimal point takes a value of 0 or 1, denoting casting and ingot respectively [4]. The main alloying elements in the AA system are as follows:

* 1xx.x series are minimum 99% aluminium
* 2xx.x series copper
* 3xx.x series silicon, copper and/or magnesium
* 4xx.x series silicon
* 5xx.x series magnesium
* 7xx.x series zinc
* 8xx.x series tin
* 9xx.x series miscellaneous


wrought/aerospace alloys.

* 7075 aluminium
* 6061 aluminium
* 6063 aluminium
* 2024 aluminium
* 5052 aluminium

notice theres no cast numbers there? so why wouldnt the aerospace program use cast aluminum? probably because its inferior...

7000 series are alloyed with zinc, and can be precipitation hardened to the highest strengths of any aluminium alloy. what we want are 7075 parts, no decimal point.