The microstructure and mechanical properties of Al-containing 9Cr ODS ferritic alloy

In this study, a 9Cr oxide-dispersion strengthened (ODS) alloy with additional corrosion resistant element Al was fabricated by mechanical alloying (MA) and hot pressing (HP) to explore the impact of Al on the microstructure and mechanical property of a 9Cr ODS alloy. It is found that the Al completely dissolved into the Fe–Cr matrix after milling for 30 h. The minor phases in the Al-containing 9Cr ODS ferritic alloy were investigated by a high-energy X-ray, and were identified to be orthorhombic-YAlO3 (YAP), bcc-Y3Al5O12 (YAG), monoclinic-Al2Y4O9 (YAM), and hexagonal-YAlO3 (YAH). These phases were further confirmed by selected area diffraction pattern (SADP), energy dispersive spectroscopy (EDS), and high resolution transmission electron microscopy (HRTEM). In addition, their volume fractions were also calculated from the integrated intensities. According to the analysis of the particles and their formation sequences, the larger particles (greater than 100 nm) are identified as mainly YAG and Al2O3 particles, while the particles with small size (less than 30 nm) are likely primarily YAM, YAH, and YAP particles. The yielding strength (YS) and ultimate tensile strength (UTS) at RT are 563 MPa and 744 MPa, respectively, while the YS and UTS at 700 °C are 245 MPa and 276 MPa, respectively. Although the addition Al in ODS alloys decreases the strength at RT, the values at high temperature are similar to those obtained for 9Cr ODS alloys strengthened by fine Y–Ti–O particles. Synchrotron X-ray diffraction line profile of the 9CrAl ODS alloy; (Ferrite matrix phases, along with minor phases, orthorhombic YAlO3 (yttrium aluminum perovskite, YAP), bcc Y3Al5O12 (yttrium aluminum garnet, YAG), monoclinic Al2Y4O9 (yttrium aluminum monoclinic, YAM), and hexagonal YAlO3 (yttium aluminum hexagonal, YAH) were recognized.). [Display omitted] •The Al-containing 9Cr ODS ferritic alloy was firstly fabricated by MA and HP.•The precipitates were identified as YAM, YAH, YAP, and YAG.•The volume fractions of precipitates were calculated by integrated intensity.•The YS and UTS at 700 °C are 245 MPa and 276 MPa, respectively.