Preliminary Discussion on Differences in Determination of Hydrogen in Aluminum and Aluminum Alloy by Different Heating Methods

There was "secondary hydrogen" phenomenon in aluminum and aluminum alloy determination by pulse inert gas melting method (hereinafter referred to as the pulse method), which meant, there was still a significant hydrogen release after reheating the measured sample. Domestic scholars tended to believe that the interference caused by the release of hydrogen from graphite crucibles, while Russia scholars tended to believe that the heating time was too short to completely release hydrogen. In order to compare the different views, hydrogen in aluminum and aluminum alloy was determined by pulse method and thermal desorption method. The results were as follows: there was still obvious hydrogen released when the samples which were analyzed by pulse method were tested again by thermal desorption method, which meant "secondary hydrogen" phenomenon. The hydrogen in aluminum reference materials GBW (E) 020030certified value （0.19±0.04） μg·g⁻¹ , GBW (E) 020030acertified value（0.24±0.06） μg·g⁻¹ , and GBW (E) 020031a certified value （0.25±0.05） μg·g⁻¹ which were certified by the pulse method, were tested by thermal desorption method, and the results were 0.38, 0.58, and 0.71 μg·g⁻¹ , with the release peaks of the former two located at approximately 450, 380 ℃, respectively; The AlSi samples from different batches were simultaneously analyzed by pulse method and thermal desorption method, with results of 0.13, 0.16, 0.16 μg·g⁻¹ for pulse method and 0.70, 0.53, 0.48 μg·g⁻¹ for thermal desorption method, respectively. The release peaks of the former two were mainly located at 350 ℃ and 580 ℃. As shown by the above results, the testing results of thermal desorption method were generally higher than those of pulse method. Considering that the former used quartz tube heating, did not involve graphite crucible and slowly heated up, and the analysis time was measured in hours, it was preliminarily believed that the viewpoint that the heating time was too short to completely release hydrogen, was more convincing. However, considering the widespread use of pulse method for determination of hydrogen in aluminum alloys in China, more detailed comparison and verification were still needed in order to obtain more convincing conclusions.