Melting preparation and hot workability of Nb10Zr alloy

For the smelting preparation and thermal processing performance of the new Nb10Zr alloy, two arc smelting and thermal simulation tests are used to study the high temperature deformation characteristics of the alloy. The following conclusions are drawn through this research:

(1) The alloy is smelted twice in an electric arc furnace, and qualified Nb10Zr alloy ingots are prepared by controlling the impurity composition of the raw materials of the niobium sheet and the zirconium sheet and the smelting process. The overall composition of the alloy ingot is relatively uniform, and only micro-segregation occurs inside the alloy. The as-cast structure is a thin, long, short and thick dendritic rod-like structure. There is obvious segregation on the large dendritic grain boundary, which contains more undissolved rich In the zirconium phase, small equiaxed dendrites are distributed among large dendrites. The ingot was homogenized and annealed at 1300°C for 24 hours, the undissolved Zr-rich phase inside the dendrites and grains was dissolved, the segregation was significantly reduced, and the grain boundaries in the structure became clear.

(2) Use the hot rolling test to explore the high temperature processing performance of the Nb10Zr alloy, the temperature is 1323K, the pass deformation is 10%, 15% and 20%, the diameter of the rolling wheel is @550mm, and the linear speed of the rolling wheel is 30mm/min. The alloy billet is uniformly deformed without obvious edge cracking, and the alloy structure is of significant hot working streamline, and recrystallization occurs. According to the hot rolling test parameters, determine the thermal simulation test process parameters. The thermal simulation test temperature is 1273K, 1323K and 1373K, and the strain rate is 0.01 s-1, 0.1 s-1, and 1 s-1.

(3) Use Gleeble-1500 thermal simulation test machine to conduct isothermal constant strain rate compression test to study its high temperature deformation behavior. Therefore, it can provide a reference for rationally controlling the hot forming process of Nb10Zr alloy, improving its comprehensive mechanical properties, formulating a reasonable hot processing technology, and providing a theoretical basis for industrial production rolling. According to the thermal simulation experiment, the true stress-true strain curve of Nb10Zr alloy under hot compression is obtained, and finally the mechanical properties and stress-strain constitutive equations of Nb10Zr alloy during high temperature deformation are established.

(4) During the hot working process, there is a softening process of recovery or recrystallization. The alloy has low deformation resistance, low energy consumption, good plasticity and toughness, and a reduced tendency to fracture. This is due to the fact that there are more systems that slip at high temperatures, so that the slip surface and the direction of the slip are constantly changing, and the hot working deformation is not easy to produce texture, which can reduce the anisotropy of the alloy structure. After the Nb10Zr alloy is deformed by hot compression, the as-cast structure is stretched into a fibrous shape, and the recrystallized grains show a tendency to merge with each other and gradually grow up. The alloy structure has yielded and softened, and the alloy structure has undergone dynamic recrystallization. Through the comparison of the microstructure pictures after rolling with three different pass processing rates of 10%, 15%, and 20%, when the pass processing rate reaches 20%, the as-cast structure is completely broken, the alloy is deformed severely, the strain rate is large, and a large amount of deformation heat is generated , The driving force for tissue recrystallization is relatively large, and the tissue is completely recrystallized to form equiaxed grains. It is recommended that the pass rate of Nb10Zr alloy sheet rolling should be more than 20%.