M. Karlik

Precipitation in the Fe–28Al–4Cr intermetallic alloy with Ce addition ☆

Abstract Annealing experiments were carried out in order to determine the temperature range for the existence of Cr–Fe–(C) and Ce-containing particles found in the structure of a hot-extruded Fe–28Al–4Cr–0.1Ce (at.%) alloy. The carbon content in the Cr–Fe–C particles ranges from 15 to 30 at.%., the Cr:Fe ratio in the matrix and grain boundary variant of the particles is 7:3, and 6:4, respectively. Cr–Fe particles without carbon were also found. The matrix Cr–Fe–(C) precipitates form as rods or rhomboidal platelets, the grain boundary particles are thin platelets of irregular shape. All Cr–Fe rich particles are completely dissolved after annealing for 2 h at 950°C, and they reappear when the quenched alloy is heated in the temperature range from 300 to 800°C. At 700°C the precipitate is already formed after 5 min of annealing. The Ce-containing particles, mostly 1–10 μm in diameter, present a broad range of compositions. Nevertheless, more than half of the analyzed particles were identified as the Fe 17 Ce 2 compound. The Ce-containing particles do not dissolve even after annealing for 6 h at 1175°C.

Atomic structure of grown-in antiphase boundaries (APB2) in the Fe-28Al-5Cr (at.%) alloy

Abstract Thermal grown-in antiphase boundaries (APBs) of the next-nearest neighbour (APB2) type in the Fe-28Al-5Cr (at.%) alloy were studied in the edge-on orientation by means of high resolution electron microscopy. The interfaces are thin and sharp. The domain walls are rugged, small facets (ledges) 0.5–5 nm long situated in the (100) and (111) planes were observed. Two different structures of the APB2 interface with opposite fault vectors were found. Their atomic arrangements are interpreted by contrast simulations, using two models of stacking of the Al and Fe planes in the boundary.