TEM study of PM 2000 steel

Abstract

Transmission electron microscopy (TEM) as well as corresponding analytical techniques, such as high resolution TEM (HRTEM), energy dispersive X-ray (EDX) analysis, electron energy loss spectroscopy (EELS) and elemental mapping via a Gatan imaging filter (GIF), have been used to study the complex precipitation morphology of the commercial Fe-Cr-Al based oxide dispersion strengthened (ODS) alloy PM 2000. Formation of homogeneously distributed Y-Al-O ODS particles from Y 2 O 3 added to the metal powder is shown. Besides these ODS particles, a large amount of complex Y-Al-O/Al 2 O 3 and Y-Al-O/TiC as well as pure Al 2 O 3 inclusions with sizes significantly larger than ODS particles have been identified. A typical feature is the growth of Al 2 O 3 and Y-Al-O particles on the surface of small Ti(C,N) nuclei. Some implications of the results obtained from the mechanical properties of PM 2000 steel are discussed.

Identification of Oxide Phases in Oxide Dispersion Strengthened PM2000 Steel

“…Average chemical composition (at.%) of these particles more than ten was about 60O, 37Al, 1Cr, 1Fe, 0.5Y, 0.5Ti, hinting that these aluminum oxides may be Al2O3 phase, as reported in ODS PM2000 steel by Klimiankou et al 12) As reported, yttrium aluminum perovskite, YAlO3 (YAP), yttrium aluminum hexagonal, YAlO3 (YAH), yttrium aluminum garnet, Y3Al5O12 (YAG), yttrium aluminum monoclinic, Y4Al2O9 (YAM), aluminum oxide, Al2O3, and titanium carbonitride, Ti(C,N) have been observed in ODS steel. [8][9][10][11][12] However, no any evidence of the presence of YAH or YAG or YAM or Ti(C,N) phase was found in the ODS PM 2000 steel in the present TEM investigation.…”

“…[8][9][10][11][12] In this paper, we reported the results for the identification of oxide phases in ODS PM2000 steel using electron micro-diffraction along with energy-dispersive X-ray (EDX) analysis.…”

Fabrication of Fe–Cr–Al Oxide Dispersion Strengthened PM2000 Alloy Using Selective Laser Melting

“…Typical oxide particle diameters found in conventionally processed PM2000 lie in the range ~10-40nm. [25] In contrast, the average size of oxide particles after consolidation of the PM2000 powder at a laser scan speed of 0.1ms -1 ranged between 54-61nm, indicating that the oxide had undergone some coarsening. High temperature coarsening of yttria-alumina oxides in ODS alloys has been shown to have a detrimental effect on the mechanical properties of the material, [26] contributing, for example, to the poor mechanical properties found in laser welded MA956 [5] and PM1000 joints.…”

Microstructural Evolution of Cr-Rich ODS Steels as a Function of Heat Treatment at 475 °C

“…The fact that no Y 2 O 3 particles were observed in any of the investigated steels is likely the result of the reaction of Al with Y 2 O 3 during the high-temperature pressing leading to the formation of Y-Al-O particles [7,12]. The exact composition and crystallographic structure of these Y-Al-O compounds depend on the local composition of the matrix.…”

“…Moreover, there is disagreement among different researchers regarding the composition and structure of these oxides in the as-recrystallized state. Some authors state that the dispersoids have a Y-Al-O composition [1,7,8], while others argue that they remain in their original form, as the Y 2 O 3 particles that were added into the matrix during the mechanical alloying process [9,10]. Possible structures of the oxide particles which can be found in ODS steels, according to the literature, are listed in Table 1.…”