Precipitation of AlN in High Purity Fe-Al-N Alloy

Abstract

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).

Texture Control in a Fe-Al-N Alloy by Thermomechanical Processing

“…Preferred (Ill ) texture is usually associated with retardation of recrystallization and with elongated or pancake-shaped grain structures. !,9,lO) On the basis of these empirical rules, as well as studies on ch emical analysis,13) internal friction , 7 ,13-15) electrical resistivi ty, 4,16,17) or electron microscopy,12,14,17-20) extremely fine precipitates of AIN or their "pre-precipitation clusters "14) are considered to be responsible for the recrystallization texture. Ujiiye et at.…”