Fabrication And Characterization Of Mg-W Functionally Graded Materials With Density Gradient

Flier-plates with graded wave impedance can be regarded as a new kind of functionally graded material (FGM), which create quasi-isentropic loading to target materials. Mg-W functionally graded materials was selected for gain flier-plates of lower wave impedance in front interface and higher wave impedance in back interface, and fabricated by spark plasma sintering technology. The processing, densification mechanism and performance of Mg-W composites will be studied.The Mg-W composites with tungsten fraction of 0～92wt% was fabricated at the condition of 600℃-30MPa-5min and the relative densities are above 98.5%. The relative density of 93wt%W/Mg composites can reach to 98.3% through grain composition (6.92μtm: 0.95μtm=3: 1).The results indicate that Mg and W are mechanically mixed because there is no metal compound created. The sintering processing is different when the fraction of tungsten varies. The sample shrinks sharply during the initial stage because of the sintering of Mg and shrinks slowly during the upper stage when the fraction of W is lower. When the sample shrinks slowly during the initial stage and shrinks sharply during the upper stage because some of the Mg particles fuse when the fraction of W is high.The sample generates spark discharge which can bring much high temperature between the powder particles because of much interspace while the temperature can reach high in the particle-contacting surface. Some Mg particles can fuse because of the high temperature. So the Mg-W composites can be fully dense due to the spark discharge between the powder particles, the high temperature generated in the particle-contacting surface and pressure.The wave impedance of Mg-W composites ranges from 8. 01 to 27. 9x 10~6kg/m~2s. Sound wave velocity range from 4.4～2.6mm/μtm and agree with the calculated data. With the increasing of tungsten, the micro-hardness range from 54.2GPa to 206GPa and 3-point-bending strength range from 73MPa to 356MPa.The Mg-W functionally graded material with density gradient which is fully dense, good planeness and no macro-crack was successfully fabricated by powder lamination and SPS technology. The W element increases along the thickness and the density range from 1.74 to 10.55 g/cm~3.