Chemical reaction assisted transient liquid phase bonding of alumina in combination with cold isostatic pressing

Abstract

A new method of transient liquid phase (TLP) bonding of alumina specimens has been developed using a mixture of aluminium powder and silica powder as insert materials. A chemical reaction of aluminium with silica occurs in the inter layer to produce alumina and silicon. Some of the specimens were subjected to cold isostatic pressing (cipping) before bonding to improve the bonding strength. Specimens with an interlayer of powder mixture were joined for Al/SiO₂ ratios of 1 : 0.84 and 1 : 0.42, but did not join for an interlayer with a theoretical ratio of 1 : 1.67. When specimens were subjected to cipping before bonding, bonds were far stronger than bonds without cipping in a temperature range from room temperature to elevated temperatures above the melting point of aluminium. In the mechanical test (bending test), fracture occurs at the boundary between the alumina matrix and the interlayer at room temperature, and in the interlayer at temperatures above the melting point of aluminium.