塑性予ひずみを与えたAl<SUB>3</SUB>Niウィスカ/Al系複合材料中の格子ひずみの中性子回折による測定

Abstract

The time-of-flight (TOF) analysis method in neutron diffraction has been applied to the study of residual stress states associated with the mechanisms of back-stress hardening and diffusional recovery in a short fiber-reinforced metal matrix composite. The composite examined was an experimental model system, Al3Ni whisker-reinforced aluminum, produced by directional solidification of the Al-6.2 mass%Ni eutectic alloy. It was cold-swaged and then annealed, so that very long (essentially continuous) whiskers changed into short fiber morphologies. Incremental strain amplitude tension-compression tests were carried out at room temperature and 500°C up to the total strain of 0.3% with final unloading from the tension side. Neutron diffraction experiment was subsequently performed to measure residual lattice strains in the deformed specimens, together with the as-annealed one as the reference material. A couple of detectors were properly arranged so as to make simultaneous measurements of lattice spacings in both the axial and transverse directions of the specimens. From the set of diffraction data, residual lattice strains and hence, residual stresses in both the axial and transverse directions were fully determined for the alminum matrix in the specimens deformed at room temperature and at 500°C; however, the corresponding residual stress states for the Al3Ni whiskers were indeterminable because of incomplete diffraction data due to the effect of preferred orientation of the Al3Ni whiskers. The results are discussed in light of independent calculations of residual stresses based on a micromechanics-based analysis of the stress-strain data in tension-compression tests.