Fracture morphology and microstructure analysis of Mo–La nozzles for solid rocket motor

The ablated Mo–La nozzle samples were obtained through the ground thermal test of solid rocket motor. The metallographic structures of the samples before and after ablation was compared and analyzed. The mechanical properties of Mo–La materials were tested at room temperature and 1000 ℃. The results show that the Mo–La nozzles used in solid rocket motor with working time of 2.1 s have the complete inner profile shape, no significant change in size, and good ablation resistance. The metallographic structure before and after ablation reminds the grain recrystallization, especially at the high working temperature position in the middle of nozzle and nozzle, and the morphology changes obviously from the slender fiber to the equiaxed grain. The molybdenum is toughened by the lanthanum oxide particles, the necking and dimple appear on the fracture surface of alloy samples at 1000 ℃ and room temperature, the dimple depth is greater at high temperature, and the tensile strength and elongation decrease.