Influence of joining time and temperature on the flexural strength of joined boron carbide ceramics

摘要

The influence of the joining time and temperature on the flexural strength of B₄C ceramics joined using an Al sheet was investigated. The B₄C ceramics were joined over a temperature range 600–1400°C for 2–72 h in vacuum (10?2–10?4 Pa) and in an Ar atmosphere. A joining interlayer with a dense structure was found in the B₄C joint formed at 1000°C after 2 h in vacuum, and mainly Al was present in this joining interlayer. On the other hand, some voids existed in the joining interlayer in the B₄C joint formed after 72 h. In addition, Al was not present in this interlayer owing to its reaction with B₄C as well as the evaporation of Al. Four-point bending tests of the B₄C joints formed at 1000°C in vacuum for periods ranging from 2 to 72 h were performed at room temperature. The average four-point bending strengths of the B₄C joints formed after 2 h at 700–1100°C were close to that of the B₄C base material, and the B₄C ceramics were considered to have successfully bonded. However, the joint strength decreased with an increase in the joining time, and the B₄C ceramics did not bond at temperatures over 1200°C in vacuum. On the other hand, the B₄C ceramics did bond at 1200–1400°C in Ar.