Niobium hafnium alloy has good processing property and high temperature performance, can be made into thin plates, bars, forging rings and complex shape parts, is widely used in rocket nozzles and other aerospace fields. The observation of the microstructure of Nb-Hf alloys is of great significance to guide the casting, machining and forming of materials. In the existing literature, there is no report on the method of metallographic observation of Nb-Hf alloys. Because the niobium hafnium alloy material is not easy to cut, the sample preparation by conventional mechanical polishing method has a long period and poor effect, and the structure with ideal contrast can not be obtained by conventional niobium etching agent.
In view of the shortcomings of the above existing techniques, a method for the observation of the metallographic structure of Nb-Hf alloys is provided, which can effectively improve the rapid sample preparation and corrosion problems of Nb-Hf alloys materials, and make the metallographic structure of Nb-Hf alloys clearly visible.
In order to solve the above technical problems, the technical solution adopted by the invention is: a method for observing the metallographic structure of niobium hafnium alloy, which is characterized in that the method includes the following steps:
(1) the observation surface of niobium hafnium alloy sample is machined into a plane, and then ground on a metallographic grinding machine. After grinding, the sand particles on the sample are washed away;
(2) The Nb-Hf alloys sample washed out of sand grains in Step (1) is immersed in the polishing solution for chemical polishing, and then washed clean with water; The polishing solution is a mixture of H2SO4, HNO3 and Hf at a volume ratio of 5∶1 ~ 2∶1 ~ 2;
(3) The chemically polished niobium hafnium alloy sample in Step (2) is placed on the polishing machine. Cr2O3 solution and diamond powder with particle size of 2.5μm are used for mechanical polishing, and then the mechanically polished niobium hafnium alloy sample is immersed in the corrosion solution for 10s ~ 15s. The corrosion solution is a mixture of H2SO4, HNO3, Hf and H2O at a volume ratio of 2∶1 ~ 2∶1 ~ 2∶8 ~ 10;
(4) The sample of niobium hafnium alloy etched by the etching solution in step (3) is observed under a microscope.
