Aluminium Castings in LM4

I have a set of aluminium castings to make the side valve 'Whippet' engine which have been cast in LM4 alloy.

I am sure these are usable as is, but seem a bit on the 'soft' side and I was hoping to harden them up in some (easy) way

Has anyone used this quite common casting alloy and done any heat treatment to it?

Alan

There is quite a bit on google. The heat treatment gives you LM-4 TF, it consists of;

Solution treatment, 6 to 16hrs at 505 to 520*C followed by quenching in hot water.

Precipitation treatment, 6 to 18hrs at 160*C then allow to cool in air.

I'm not that sure if there would be a great advantage, but you would have to study the information, I don't think it makes much difference to the hardness of the metal, it proberbly improves the grain structure of the metal. Ian S C

The copper content of LM4 allows it to precipitation harden. The copper precipitates inhibit the movement of dislocations which means that the metal will be harder and tougher. If you have equipment that will allow you to closely follow the recipe that Ian has given I'm sure that would be beneficial, otherwise I would recommend leaving it in the as cast state. Some natural age hardening is likely to occur over time anyway.

Rod

Thanks guys, I did do an internet search and found what you have, I was after something simple! as I dont have the facilities to carry out this process.

I shall use them as is and go carefull with the machining to avoid pickup and possible problems with tapped holes.

Alan