抄録
An investigation has been made on the precipitation of AlN in vacuum melted iron wires, contAlNing 0.003, 0.036 and 0.072 pct Al, solution-treated at 1 200°C, cold reduced to 70 pct and isothermally annealed in the range 500°C to 700°C. To determine the behaviour of AlN in αiron, the technique of low frequency internal friction measurement was employed. Separation of the Snoek peaks observed by this technique allows accurate determination of the amounts of dissolved carbon and nitrogen in solution. The results obtAlNed were summarized as follows:
(1) In specimens initially contAlNing 0·003 pct Al, purified and nitrided to 0·018 or 0·052 pct and subjected to a solution treatment, increased the amount of dissolved nitrogen during isothermal annealing at 600°C after cold reduction. In specimens carburized to 0·012 or 0·019 pet, the dissolved carbon tended to decrease to the solubility limit by the same heat treatment.
(2) It made a little difference in the behaviour of AlN precipitation during isothermal annealing whether AlN particles were completely dissolved in γiron by a solution treatment at 1200°C or undissolved partially. In both cases, when annealed at 600°C, however, AlN precipitation occured during the recovery and in the early stage of recrystallization and the recrystallization was retarded.
(3) On annealing the nitrided specimen at 700°C, recrystallization preceded the precipitation of AlN.
It was found that pre-precipitation clustering of AlN at dislocations and subboundaries in deformed by αiron preheat-treatment for 20 hr at 500°C prior to 700°C annealing did significantly affect the recrystallization process due to promoting AlN precipitation and decreasing the recrystallization rate.
