Radiation damage to aluminum and aluminum alloys.

摘要

An evaluation of proton and neutron damage to aluminum and various aluminum alloys has been performed. The proton studies were conducted at energies of 200-MeV, 800-MeV, and 23.5 GeV. The proton studies consisted of evaluation and characterization of proton irradiated window/target materials from accelerators and comparison to non-irradiated archival materials. The materials evaluated for the proton irradiations included 99.9999 wt% aluminum, 1100 aluminum, and 5052 aluminum. The neutron damage research centered on 6061 T-6 aluminum which was obtained from a control rod follower from the Brookhaven National Laboratory's (BNL) High Flux Beam Reactor (HFBR). This material had received thermal neutron fluence up to {dollar}spsim{dollar}4 {dollar}times{dollar} 10{dollar}sp{lcub}23{rcub}{dollar} n/cm{dollar}sp2{dollar}. It is shown that the large increases in tensile strength with decreasing elongation and notch impact resistance can be attributed to the development of a precipitate of amorphous silicon in the alloy matrix. This precipitate is produced radiogenically and approaches 8 wt%. The precipitate can be transformed into a crystalline structure with applied heat treatment. The nucleation of this amorphous phase is discussed and the spherical shape of the silicon precipitate is evaluated. The effects of thermal-to-fast neutron flux ratios are also discussed. The increases in tensile strength in the proton irradiated materials is shown to be the result of atomic displacements. These displacements cause interstitials which aggregate into defect clusters which result in radiation hardening of the materials. The size and effects of displacement cascades are considered relative to the hardening of the aluminum alloy. Production of gas (helium) in the grain boundaries of proton irradiated 99.9999 wt% aluminum and the potential for liquid metal embrittlement are reviewed. The metallurgical and mechanical property evaluations for the research consisted of electron microscopy (both scanning and transmission), X-ray diffraction, tensile testing, microhardness testing, Charpy impact testing and single-sided notch tensile testing.