Can I use Araldite to stick PLA to metal frame?
Araldite is a brand that refers to a range of structural epoxy, acrylic and polyurethane adhesives. Among the vast number of products marketed under the name are also "metal repair" paste and what seems to be silicone based glues. Depending on what Araldite you have on hand, all of these types can be useful for PLA and any other 3D-printing material, as I had elaborated here. I suggest grabbing either an epoxy or PU variant or some kind of silicone for this use. You should make sure several things though if you go with epoxy or PU:


make a small sample print and clamp down one side, then put a small weight on the other side. Apply the glue in the center of it. If it sags considerably during the bonding, the heat of the glue curing is warm enough to soften the print. If this happens, you should take precautions to prevent it from deforming during the bonding, e.g. not apply too much pressure onto the bond.
The MOSFET can get rather hot. Make sure that the clamp holding the MOSFET still holds the item as it gets hot, as PLA starts to get malleable enough to deform under stress at 50 °C and usually fails quickly at about 100 °C. 


Silicone-based glues depend on an area to force ratio to stick but offer a flexible bond that is somewhat thermal resistant and very gap filling.