Microstructure characterization of W-Ni-Fe heavy alloys with optimized metallographic preparation method

Tungsten heavy alloys (WHA) have been widely adopted in many engineering applications due to their excellent physicochemical properties. Microstructure characterization is a very powerful method ranging from testing materials properties to detecting material failures and defects. However, the microstructure of WHA was not well characterized with the sample prepared by conventional method of etching with strong acids, bases or oxidant after polishing for the coarse surface. To solve the problem, the exact characterization of W-Ni-Fe heavy alloys microstructure was conducted using the sample prepared by optimized polishing method. A series of experiments were conducted to find the suitable polishing conditions including polishing pad, abrasive slurry and slurry pH. The results show that a smooth and clear microstructure sample was obtained by polishing with alkaline colloidal silica and IC polishing pad, which contained few defects compared with that obtained by conventional method of etching after polishing. The microstructure of W-Ni-Fe heavy alloys was analyzed by XRD, EDS tests and EPMA detection. The slipping phenomenon was observed in nanoindentation test using the prepared sample for the first time and the mechanism of satisfactory microstructure sample preparation was illustrated.