Low Temperature Brazing Between Pre-Metallized ZrO2 Ceramics and Medical Pure Titanium Using AuSn20 Filler Metal

ZrO2 ceramic was metallized by Sn-xTi (x = 2, 3 and 4 at.%) foils at 1000 degrees C for 30 min. As the Ti content was 3%, the continuous and homogeneously distributed Ti-O compounds layer formed at the interface. The metal-lization layer metallized Sn-3Ti foil consisted of Ti2O3 layer + Ti11.31Sn3O10/beta-Sn + Ti2Sn3+Ti6Sn5. During the metallization process, as the thickness of metallization layer increased, the Ti-O and Ti-Sn-O layers became continuous, Ti2Sn3 and Ti6Sn5 phases increased and aggregated obviously. Vacuum brazing using AuSn20 filler metal after pre-metallization were utilized to achieve the robust ZrO2/Sn-3Ti/AuSn20/Ti joints. The effect of the metallization layer thickness on microstructure and mechanical properties was systematically examined. The typical interfacial microstructure of ZrO2/Sn-3Ti/AuSn20/Ti joints brazed at 550 degrees C for 30 min was ZrO2/ Ti2O3+Ti11.31Sn3O10/beta-Sn + Ti6Sn5+AuSn2+AuSn4+AuTi5Sn3 layer/Ti. During brazing process, the Ti-O and Ti-Sn-O layers beside ZrO2 ceramic varied barely with the increasing of the thickness of metallization layer during brazing process. In the brazing seam, the AuSn2 phases and Ti6Sn5 phases attenuated whereas AuSn4 phases evidently increased with the thicker metallization layer. The AuTi5Sn3 layer nearby the Ti substrate thickened significantly varied with the thickness of metallization layer. Additionally, the ZrO2/Ti brazed joint with the maximum shear strength of 48.6 MPa was achieved by the metallization layer thickness of 150 mu m. Furthermore, fracture analysis demonstrated that the cracks initiated at the Ti-O layer and propagated along the AuSn2 phases and layered Au-Ti-Sn phases.