Once a small amount of carbon, nitrogen, and oxygen is introduced into the body centered cubic (BCC) metal during preparation or service, it will cause significant hardening and embrittlement, but its microscopic mechanism has always been a mystery. Recently, the research team of the School of Materials of Xi'an Jiaotong University has solved the mystery of oxygen embrittlement of body-centered cubic metal niobium. The related results were published in the top journal of metal materials entitled "Mechanism of hardening and damage initiation in oxygen embrittlement of body-centred-cubic niobium" Acta Materialia.
Paper link: https://www.sciencedirect.com/science/article/pii/S1359645419301168
Metals with BCC structure have the advantages of high melting point, high strength, and resistance to radiation, and are widely used in industry. Take metal niobium (Nb) as an example. As a typical refractory metal, it has the advantages of high melting point, good thermal strength, low density (compared to other refractory metals), and good processability. Wide application prospects, widely used as key heating parts such as flame nozzles of space launch equipment. However, intense oxygen absorption under high temperature conditions will cause hardening, embrittlement and oxidation of niobium, which brings great challenges to the application of niobium alloys.
Block tensile sample and fracture morphology
Over the years, researchers from various countries have used various methods to try to elucidate the oxygen embrittlement mechanism of body-centered cubic metals, but progress has been slow. In order to solve this problem, researchers at the Center of Micro-Nano of Xi'an Jiaotong University have combined the research methods of macro-mechanical behavior with micro-nano-scale in-situ mechanical performance analysis and atomic-scale simulation to systematically study the mechanics of solute atomic oxygen on niobium The effect of deformation behavior clarifies the influence of solute atomic oxygen on the agglomeration of point defects, screw dislocation movements and permanent damage nucleation process in metal niobium, reveals the microscopic mechanism of metal niobium hardening and embrittlement caused by solute atomic oxygen, and builds the metal Clear physical image of niobium oxyembrittlement. The newly discovered micro-mechanism of oxygen embrittlement by researchers has important reference value for clarifying the hardening and embrittlement behavior of other body-centered cubic refractory metals during deformation and irradiation.
Nanomechanical tensile test and submicron scale Nb and Nb-O under TEM
The random force field caused by oxygen on the screw dislocations can strengthen the formation and hardening of interactive entanglement and point defects
This work was co-funded by the National Key Research and Development Program, the National Natural Science Foundation of China, and the 111 Program of the State Administration of Foreign Experts Affairs. Professor Jia Chunlin, Professor Mi Shaobo and Lu Lu engineers from Xi'an Jiaotong University provided useful discussions on the characterization of solute atomic oxygen.