Abstract
Two series of Fe-0.01, 0.03, and 0.1% Al-0.015% N alloys with either 0.01 or 0.002% C, were usedto study the states of AlN precipitates and their effects on the yield point of x-iron. Results obtained areas follows.
(1) AlN is mostly precipitated in the temperature range between 800 and 900°C during isothermalafter solution treatment.
(2) Carbon content affects the amount, shape, size, and dispersion of AlN precipitates.
(3) Variation of yield point is well explained by the individual contributions of AlN precipitates andof dissolved nitrogen.Investigation on ductility and work hardening of extra low carbon Fe-Al-0.01% N alloys with Al contentsvarying from 0.005 to 1% leads to the following conclusions.
(4) The behavior of dissolved nitrogen as revealed by internal friction suggests that the reversion of AlNprecipitation occurs.
(5) In the same heat tretament that will cause the intergranular brittle fracture, ductility can be improvedby fixing the more amount of nitrogen. In the ductile states, the contribution of AlN precipitates toductility is the greater, the smaller their effect on hardening is.
(6) Grain size is the main factor influencing work hardening; nitrogen in solution or fine AlN particlesincrease the work hardening rate, while grown precipitates and quenched-in dislocations decrease it.
