AA319 - Mechnical Properties

[HBair]

We have recently begun T-6 heat treating a AA319 sand casting and have realized part to part variation in YS and UTS. We have looked at all sources of heat treatment variation such as solution time and temp, quench speed, quench temperature, aging time temp and part orientation. To date, we have not found correlation which may explain mechanical property variation.

Not being overly familiar with foundry practices, can anyone provide information that would assist us in quantifying/confirming that this variation is not a result of the casting processes. What should we be looking at to confirm that the casting quality is consistent? Outside of chemistry, what casting parameter would influence mechanical properties?

 

[NickE]

One phrase describes the variation you're seeing.....

"Solidification Rate"

IE: Teh solidification rate usually governs the scale of the dendritic structure. Usually higher solidification rates produce shorter denrite arm spacings which translate into smaller grain size which translates into higher strengths before heat treat.

Admittedly I'm just expounding from the basics.

I would think that you might wnat to check into your green sand process. Variations in mold density will translate into variations in solidification. Also section size and gating/risering will tend to alter solidification.

other than grain structure differences have you looked at porosity and inclusion content? They will affect as cast properties I'm not sure about the effects after heat-treat....


Good Luck



Nick
I love materials science!