Actually there are two questions, but they are in the same framework.
I want to do some study may or may not related to the vacancy concertration of mangesium alloy. If I dip a large specimen into a salt bath, say 400℃, and I can monitor the real time temperature of the specimen until it got to 400℃, after that how much time shold I keep the specimen there to get it's concentration as high as the equilibrium? In minutes or hours?
On the other hand, when I get the specimen out of the bath and hold it in the room temperature air to get specimen temperature falling naturally, there must some kind of lag of it's real value compared with the equilibrium state, and it is reasonable that the lag differs if the colling rate vary. I read the paper Interaction between solute magnesium atoms and vacancies in aluminium, it says “air-cooling or furnace-cooling giving no trapping of vacancies, on the contrary, brine-quenching appears to trap probably all the vacancies, ”. I'd like to have more details on this subject.
Looking forward any discussion on it.
Are you interested in Mg alloys or Al alloys containing Mg ? The vacancy behaviour in the two systems are very different. Mg traps vacancies in Al alloys so there is some intereactions related effects
There is a good paper on vacancies in pure Mg that may help you ACTA METALLURGICA, VOL. 22, (1954) p 657. There is some work on vacancy solute interactions in Mg based systems using first principles by C Wolverton and his group. Please have a look these papers may help answer your questions
What the mass of specimens are used in your expetiments? Evidently you should keep the specimen as long as the equilibrium of points defects (including vacancy concentration) is established. It should take into account a value of the diffusion coefficient at high temperature and based on it to calculate the holding time. Perhaps you can try to quench your sample to room temperature thus a set of the defects (formed at high temperature) will be saved at room one.
Thank you C.L. Mendis.
I am interested in Mg-9Al, and I noticed the vacancy-trapping effect of Mg in Al alloys, so maybe this question got a little bit messy.
Your recommendation is deeply appreciated, the right paper to read. Also thanks for the group you refered, details on solute-vacancy binding may give more than what I need.
The Acta mentioned and file are here for other people interested in this quesiton.
Hampshire J M, Hardie D. Hardening of pure magnesium by lattice defects[J]. Acta Metallurgica, 1974, 22(5): 657-663.
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