The Precipitation of AlN in Austenite and the Hardenability of Boron-Treated Steels
1978 Volume 64 Issue 8 Pages 1153-1161
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1978 Volume 64 Issue 8 Pages 1153-1161
The aluminum nitride precipitation in austenite and its effect on the hardenability of low-carbon-1/2 moly bdenum boron-treated steels has been investigated. The results are as follows:
(1) The precipitation of BN occurs under non-equilibrium condition in the case of shorter austenitizing time and consequently lowers hardenability. Such non-equilibrium BN precipitates transform to AlN with increasing the austenitizing time, resulting in the recovery of hardenability.
(2) The recovery of hardenability is due to the increase of the soluble boron content accompanied by the formation of AIN.
(3) The orientation relationship between AlN and austenite is given as:
[0001] AlN// [110] γ-Fe growth direction
(1120) AlN// (111) γ-F
(1100) AlN// (112) γ-Fe
The degree of misfit is very small along the [0001] AlN (// [110] γ-Fe) direction, leading to the preferential growth of AIN along this direction.
