Microstructure and high-temperature mechanical properties of second-phase enhanced Mo-La2O3-ZrC alloys post-treated by cross rolling

Excellent high-temperature mechanical properties and high recrystallization temperature are crucial for molybdenum (Mo) alloys in practical applications. The microstructure and high-temperature mechanical properties of Mo-0.8%La2O3-2%ZrC alloys prepared by traditional powder metallurgy technology associated with cross rolling post treatment were investigated. Results showed that the Mo1950-rolled alloys had a fine grain size of about 1.65 mu m due to hot cross rolling and high tensile strengths of 988 MPa and 189 MPa at room temperature and 1400 degrees C, respectively. SEM and TEM examinations indicated that although most of the large La2O3 and ZrC particles were distributed along the grain boundaries, some nano-sized particles were well dispersed in intragranular zones. Particularly, dislocations were found to intercepted by the second phase particles in tensile samples, which could effectively enhance both the tensile strength and recrystallization temperature. Dislocation, grain refining, and second phase particles were all found to play important roles in strengthening the alloys below the recrystallization temperature, while second phase particle strengthening was the only strengthening mechanisms above the recrystallization temperature. (C) 2019 Elsevier B.V. All rights reserved.