Quantitative Detection of Hydrogen Gas Release during Slow Strain Rate Testing in Aluminum Alloys

Abstract

We have developed a new testing device which is capable of detecting hydrogen gas release during slow strain rate tensile testing (SSRT) under ordinary pressure. The device is composed of an SSRT machine equipped with a closed chamber with an inspection window that is connected to gas chromatography with a semiconductor hydrogen sensor. Local strain distribution in the specimen during the SSRT is monitored dynamically with a digital image correlation (DIC) method. Hydrogen was pre-charged to aluminum alloys by means of friction in water process. Using the device, it was shown that hydrogen was released particularly in the stage of plastic deformation and fracture. In addition, the hydrogen gas release at the moment of fracture was clearly increased when the alloys were hydrogen-charged and tested at a slow strain rate. When we calculated hydrogen gas release from the fracture surface in Al-Zn-Mg base alloys tested at 3.3×10-6 s-1, the hydrogen amount was estimated to be 6.24×10-10 mol /mm2 in a hydrogen-uncharged alloy, and 1.30×10-9 mol / mm2 in a hydrogen-charged alloy.