1990 Volume 30 Issue 12 Pages 1124-1129
In order to join Al2O3 with iron, an Fe-M2O3 composite (I) as an interlayer was applied. Here, M2O3 represents for Y2O3, Al2O3 and Y2O3·Al2O3. The Al2O3/I/Fe joint was prepared by hot-pressing. In the case that M2O3 is Y2O3, Al2O3/I/Fe joining can be completed through formation of a series of reaction sublayers: at the interface of the Al2O3/I, a chemical reaction sublayer, next to Al2O3, including iron, aluminium and oxygen is formed; and then next to it has a second sublayer of yttrium, aluminium and oxygen matrix mixed with dispersed iron as a different phase, the Fe-M2O3 interlayer and subsequently the I/Fe interface, where the inter-diffusion of iron has occurred. The thickness of second sublayer changes with the Y2O3 content. This layer plays a role in relieving thermal stress caused by a different thermal strain of Al2O3 and iron bulks, but the increase of its thickness makes the joint easier to break. With increase in Y2O3 content in Fe-Y2O3 interlayer, the layer tends to agglomerate, which results in the weakening of the joint. To bring the thickening of the reaction layer and the agglomeration under control, Fe-Y2O3·Al2O3 interlayer was found to be effective. For analysis of the boundary region, electron probe microanalysis (EPMA) was used. Tensile strength and thermal expansion for Fe/I/Fe, Al2O3/I/Al2O3 joints and Fe-Y2O3 composite sintered materials were measured.