Proceedings of the Third International Conference on Metals & Hydrogen I02

Proceedings of the Third International Conference on Metals & Hydrogen I02

Detection of Hydrogen Trapped at Intermetallic Particles in an Aluminum Alloy by Secondary Ion Mass Spectrometry and Thermal Desorption Analysis

Junichiro Yamabe (1)1(2)2(3)3 , Tohru Awane (2)2(4)4 , Yukitaka Murakami (5)5

  • (1) 1

    International Research Center for Hydrogen Energy, Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka 819-0395, Japan

  • (2) 2

    Research Center for Hydrogen Industrial Use and Storage (HYDROGENIUS), Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka 819-0395, Japan

  • (3) 3

    Hydrogen Materials Laboratory (HydroMate), Research Promotion Division of Energy and Environment, National Institute of Advanced Industrial Science and Technology (AIST), 744 Moto-oka, Nishi-ku, Fukuoka 819-0395, Japan

  • (4) 4

    Kobe Material Testing Laboratory Co., Ltd., 47-13 Nii-jima, Harima-cho, Kako-gun, Hyogo 675-0155, Japan

  • (5) 5

    Emeritus Professor, Kyushu University

Abstract

Hydrogen trapped at intermetallic particles (IPs) in an aluminum alloy, 6061-T6, was visualized by secondary ion mass spectrometry (SIMS) and the desorption energy of hydrogen (Ed) trapped by the IPs was identified by thermal desorption analysis (TDA). Hydrogen trapped in metals often causes a degradation so-called hydrogen embrittlement (HE). However, it is very difficult even with SIMS to visualize the exact hydrogen trapped in metals, because hydrogen background (HBG) exists even in high vacuum chambers and also on sample surface, mostly in the form of H2O. To avoid the interference of the HBG, we performed a unique continuous pre-sputtering (pre-digging) by SIMS into a sample in combination with silicon sputtering prior to the SIMS measurement of the sample. We succeeded in visualizing the exact signal of hydrogen trapped by IPs at the subsurface layer of the sample charged in high-pressure hydrogen gas. The TDA also clarified that the value of Ed was 200 kJ/mol or higher, which was extremely higher than the values of Ed for lattice interstice, dislocations, and vacancies. High hydrogen concentration was trapped at IPs in the subsurface layer in contact with the hydrogen gas. This trapping nature causes an extremely low effective hydrogen diffusivity of the 6061-T6, of the order of 10-14 m2/s even at 200oC. It may eventually give a high HE resistance for this alloy.

Keywords

  • hydrogen trapping
  • aluminum alloy
  • intermetallic particle
  • secondary ion mass spectrometry
  • thermal desorption analysis
  • hydrogen embrittlement

Introduction


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