| Powder metallurgy and pressure processing technology were used as the main method, hydrogen reduction molybdenum powder was chossed as raw material and suppressed by cold isostatic press and sintering at low-temperature and then deformed and densified by rotary forging. A good performance of fine-grained pure molybdenum bar and a preparation of low-cost, small grain, high-performance molybdenum bar new method were achieved.Based on fine-grained molybdenum blank sintered at low temperature, the densification was explored by rotary forging. The capacity of hot deformation, the mechanism of hot deformation and laws of densification and the mechanism and laws of strengthening of low-temperature sintering fine-grained molybdenum blank were studied. Microstructure, property and changes and the effect on microstructure and property by hot deformation and follow-up of heat treatment were researched.The results showed that the relationship between pressing pressures and pressed densities of Mo powders under isostatic cool pressing accords fully with huang's formation theory.The results showed that, ordinary Mo powder sintering at 1600℃, for 2 hours, can achieve fine-grained molybdenum blanks. Sintered density can reach 8.4 g/cm~3 and the tensile strength reached 380 MPa. A follow-up rotary forging process can be carried out with pack added to blank.The relative density of ultra-fine Mo powder sintering at 1400℃for 2 hours, can reach 9. 4 g/cm~3, the tensile strength reached 550 MPa. Directly rotary forging can be carried out without pack.The results showed that the deformation temperature and pressure were two of the main influential factors of processing conditions for fine-grained molybdenum blank by hot deformation, and the parameters of rotary forging die also significantly affect the rotation of the forging process and the property after the forging. To choose the right deformation temperature, the compression ratio, the total compression ratio, design and reasonable rotation parameters of forging die were the key issues.The fine-grained molybdenum blank of low density was deformed and densified by a large compression ratio rotary forging to increase the density and strength. The properties were regulated by heat treatment finally. So that grain was lengthened and fibrosised by rotary forging. Internal boundary impurities segregation decreased significantly. The effect on performance by the compression ratio of hot forging was studied. It showed that strength and elongation increased with the increase of deformation after the rotary forging. |
