Wires of Fe-0 .09wtO oAI-O.O I wt O oN alloy were cold-drawn by 68.6 % reduction in area after solution treatment of J 250°C X J hr and quenching into ice water.A large decrease in electrical resistivity was observed in a tem/)erature range from 450° to 620°C in 10°C-JO min isochronal annealing, which was attributed to the /n-ecip itation of AI N . This temperature range was about ] OO°C lower than that in unstrained specimen. The dissolution qf Cottrell atmospheres, which had beenJarmed by strain aging at low temperatures was not observed bejare the precipitation of AI N.T he precipitation process q{ AIN in a deformed matrix obeyed the law of fmt order kine tics after a cerlain /)eriod of time in isothermal annealing below about 580°C. T he activation ene~I!Y obtained for the jirst order process was 58 kcal jmol, which suggested that the rate of the precipitation of AI N in a dejarmed matrix was controlled b)1 the diffusion of aluminum in Q -U'On. .T he precipitates qf AI N of cubic lallice structure were occasionally found in the early period ofJJI"eci/)itation /)rocess, but AI N precipitated mainly in the hexagonal lattice structure.R eclystalliZfltion was inhibited strongly by the jine precipitates q{ AI N formed along dislocations, whichever the c,:rstalline structure was.
Sy n op sisHigh purity I'c AI~N alloys were prepared lIsing ::.one-refined iron ( > .9.9,,9.9~ 0), and the /Jrecipitation process of AIN was studied. T wo kindf of s/Jecimens were /Jre/Jared; one was as quenched q!ler a so/uliontrealment at I 25() Cfor i hr and anolher was as cold-worked after quenching . ,-!fter Ihese s/Jecimens were annealed isochronally . the change in electriail resistivily was measured in liquid nitrogen. .-1 large decrease in resistivi(y was !ound in Ihe tem/Jerailire range from -IO{), to 70()O C, and the large decrease shifled to a lower tem/Jerature when Ihe s/)ecimen was coldworked. The as qllenched specimens were isothermally annealed at several temperatures between 6()() and 7()() C . Ihe range where Ih e Imge decrease of the resistivity was noted in the isochronal annealing. The changes in electrical resislivi!.), and internalfriction were measllred, and /JI'eci/Jitates were examined b), the extraction replica method. 77te results oblailled were as follows:(I) Actir'ation energy of the /Jreci/Jilatioll /JI'ocess is 53 kcal mol.(2)i n this /Jrocess an incubation /leriodfor lIucieatioll exist., '. The ap/Jarent order of the chemical reaelioll ( r ) for Ihis /JI'ocess. derived from -dn jdt=n rK, is about unity. (-I) The normalized resistivity change coincides wilh the 1I0mwli;:ed change in. the nitrogen. Snoek peak. (5) !l10st of the /mcifJitates are of the hexagonal structllre. alld the /neci/Jitates of cubic structure are observed in rare cases in the initial period where a large decrease is seen in electrical resistivi!.)" From these results , it was concluded that the lGlge decrease in resistivity was to be attributed to the /Jreci/Jilation of A IN, that the rate of the fHocess was controlled b), dijJilSioll of aluminum atoms in a -iron. and that the process could be eX/JI'essed b), an equation of chemical reaction, Al + N -+AIN , with unequal initial cOllcentrations of reactants. The last conclusion was confirmed b), eX/Jerimellls on a lower aluminum content 0110)' ( Fe~0.02AI~ N).
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