Flux-Free Brazing of Aluminum Alloys under Ultra-Low Oxygen Partial Pressure through a Zirconia Oxygen Pump

Abstract

Flux-free brazing of aluminum alloys was carried out under high purity nitrogen gas with ultra-low oxygen partial pressure prepared by zirconia oxygen pump. The flux-free brazability of the aluminum alloys was improved by adding a small amount of magnesium into the sample, which was more effective in the core alloy than in the brazing filler alloys. Higher heating rate of the sample increased the fillet length. When the oxygen partial pressure of atmospheric gas was much reduced to the order of 10 ¹25 Pa using a zirconia oxygen pump, a long fillet, comparable to that formed by flux brazing, was obtained. The reason for the improved brazability was discussed from the viewpoint of the fine segmentation of the oxide caused by the combined effects of reduction of the oxide, thermal expansion at melting the filler alloy, and gas phase formation reaction from the molten filler alloys.

Formation and Detection of Hydrogen by Oxygen Discharge Using Oxygen Pump-Sensor

“…Specifically, hydrogen was measured in situ using an oxygen pump sensor containing yttria-stabilized zirconia, which is a solid electrolyte. These measurements showed that even a small amount of hydrogen can be accurately measured [37][38][39][40][41].…”