Precipitation in an Al-300 ppm Fe Alloy

Abstract

Precipitation in deformed and undeformed Al-300 ppm Fe alloy has been investigated by means of resistivity measurements and transmission electron microscopy. The undeformed specimens were solution-heat-treated at 913 K for 3.6 ks, quenched in iced water and then aged at the temperatures between 393 and 848 K, while the deformed specimens were cold-drawn for resistivity measurement or cold-rolled for TEM observations after the same solution heat treatment, and then aged. Resistivity in the undeformed specimens decreased in two stages, while in the deformed specimens, resistivity decreased in two or three stages depending on aging temperatures. Time-Temperature-Precipitation (TTP) diagram for the undeformed specimens consisted of one C-curve which corresponded to precipitation of stable Al 3 Fe. The TTP diagram for the 65% cold-drawn specimens was separated into two C-curves: the curves in high and low temperature ranges corresponded to precipitation of Al 3 Fe and Al 6 Fe, respectively. The precipitation of metastable Al 6 Fe was observed only in the cold-rolled specimens. Acceleration effects of cold drawing on Al 3 Fe precipitation were hardly recognized.

Age Hardening in Ultrafine-Grained Al-2 Pct Fe Alloy Processed by High-Pressure Torsion

“…More so, it was not possible to make a clear distinction which was the dominant phase at the peak hardness because both phases were present at the initial state after casting. It was reported for solid solutions of Al-0.05 pctFe [47] and Al-0.03 pctFe [48] alloys that precipitation from recrystallized structures is mostly Al 3 Fe, whereas in the deformed structures by cold rolling, Al 6 Fe always precipitates first. A similar conclusion was reported for precipitation from supersaturated solid solutions obtained by RQ.…”

“…Precipitation kinetics in this study may be evaluated using the following equation and compared with past reports for the recrystallized and cold-worked Al-Fe alloys: [47,48] x…”

The development of alumina-forming austenitic stainless steels for high-temperature structural use

“…6 AFA 3-3 (3Al/0.6Nb/26Ni) was more oxidation resistant at 900°C in air than AFA 3-2 (3Al/0.6Nb/0.1Ti/20Ni), with comparable aluminum and nio- results from MC carbide formation. 3 Preliminary computational thermodynamic calculations suggest that in the 4 wt.% aluminum alloys, MC carbide precipitation may reach an optimum at the 1.5 wt.% niobium level. 7 Based on the trends observed, niobium ranges of ~1-3 wt.% are of primary interest for applications requiring a balance of creep and oxidation resistance, with the higher niobium levels in this range favoring oxidation and the lower levels favoring creep resistance.…”

“…[3][4][5][6][7] The alloys were manufactured by arc-casting (200 g or 1 kg castings) which were then solution heat treated in the 1,200-1,250ºC range, cold worked 40-70%, and recrystallized at 1,200-1,250ºC to control alloy grain size (nominally ~50 µm to 150 µm size range). Surprisingly, niobium additions appeared to be the key to oxidation resistance, 4 particularly in water-vapor containing environments.…”

“…The studies reported [1][2][3][4][5][6][7] were made on small laboratory-scale arc-melted castings. Efforts are being initiated to determine if similar properties can be achieved in AFA alloys made by more commercially viable methods in larger scale castings.…”