| The key to get a high quality joint is to relieve the thermal residual stress because of the physical properties difference between ceramic and filler metals, so as to avoid joint cracks and improve the joint strength. In this paper, an in-situ Ti B whisker reinforced method is developed by using Zr B2 itself and additional boron powder as B source. By regulating the distribution of Ti B whisker, the stress in the joint is changed. The microstructure of the joint is analyzed, and the mechanical properties of the joint is evaluated by finite element simulations and mechanical tests.When using Zr B2-Si C ceramic itself as boron source, a Ti Bv whisker reinforced reaction layer is generated in the interface and the Ti B whisker is perpendicular to the interface. The thickness of the layer increases with increasing temperature.When reaching a critical value, Ti B whisters dissolve and(Ti,Zr)B2 phase is generated after futher raising the temperature. A joint filled with Ti B whiskers is formed when a proper bonding temperature and Ti foil thickness are found.The acidic suspention in the electrophores is formulated and the boron powder electrophoretically deposited on Ti foil is achieved. When using addional boron powder as B source, multi-layer Ti foils with boron are used as intermediate layers.The thickness of Ti Bv whisker reaction layer increases in the interface, and Ti B whisker reaction layers is formed in the joint. Most of the Ti B whiskers in the joint have small aspect ratio, the rest of them with larger aspect ratio are generated through the reaction layers. Holes are found at the reaction layers in the joint at lower temperature while disappear with increasing temperature. The content of boron in the joint has a tendency to diffuse to the interface and the thickness of the reaction layers in the joint decreases.The Zr B2-Si C ceramic is successfully bonded to Nb with Ti foils with boron powder. The microstructure of the ZS/Nb joint in lower temperature is ZS/Ti B+(Ti,Zr)2Si+(Ti,Nb)SS/Ti B+Nb while it is ZS+(Ti,Nb)SS/Ti B/β(Ti,Zr,Si)SS+(Ti,Nb)SS/Nb B+(Ti,Nb)SS/Ti B+Nb(Ti,Nb)B2/Nb B+Nb when the temperature rises to 1300 ℃.Ti B whiskers dispersed in the joint and mainly distribut along grain boundaries. The content of Ti B whiskers increases with the increase of the boron addition to a certain extent. Holes appeare when boron addition is too much resulting in the decrease of the joint strength.The stress distribution in the joint is simulated by finite element method.Results show that the generation of Ti B whiskers don’t change the stressdistribution at the interface. Shear tests are employed to evaluated joint strength.Ti B whiskers absorb large amounts of energy and the crack deflection which improves the joint shear strength. The strength of ZS/ZS joints reinforced by Ti B whisker array reaches 203 MPa and ZS/Nb joints reaches 175 MPa. |
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