A Comparative Study of the Impact of La2O3 and La2Zr2O7 Dispersions on Molybdenum Microstructure, Mechanical Properties, and Fracture

Tkachenko, S., Slámečka, K., Bednaříková, V. et al. A Comparative Study of the Impact of La₂O₃ and La₂Zr₂O₇ Dispersions on Molybdenum Microstructure, Mechanical Properties, and Fracture. J. of Materi Eng and Perform (2024). https://doi.org/10.1007/s11665-024-10300-4

Abstract

We report, for the first time, the effect of lanthanum zirconate (La₂Zr₂O₇) particles on the microstructure and mechanical behavior of an experimental molybdenum oxide dispersion-strengthened alloy. The focus was on the preparation of the novel Mo–La₂Zr₂O₇ composite using high-energy ball milling and spark plasma sintering and on the comparison of its microstructural and mechanical properties with pure Mo and Mo–La₂O₃ ODS alloy counterparts. Mechanical properties were assessed using a Vickers hardness test at room temperature and a three-point flexural test in the temperature range from −150 to 150 °C. The microstructure of the studied materials and their fracture behavior were evaluated using x-ray diffraction, energy-dispersive x-ray spectroscopy, and scanning electron and transmission electron microscopy. The strengthening effect of La₂Zr₂O₇ particles was found to be lower than that of La₂O₃ particles, resulting in a 30-35% lower yield stress and flexural strength of the Mo–La₂Zr₂O₇ alloy compared to the Mo–La₂O₃ alloy. The experimental Mo–La₂Zr₂O₇ alloy exhibited low plasticity and no distinct ductile-to-brittle transition temperature (DBTT) in the tested temperature range, unlike pure Mo and the Mo–La₂O₃ alloy, which had the DBTT of 63 and 1 °C, respectively. Fracture occurred mainly in a brittle intergranular manner in the entire testing temperature range, while the counterpart materials showed localized plastic stretching at grain boundaries and within grains at and above the transition region. The observed behavior was primarily related to lower strengthening and brittleness as well as less effective grain boundary purification.

   https://doi.org/10.1007/s11665-024-10300-4