FIBER PHASE-TRANSFORMATION AND MATRIX PLASTIC-FLOW IN A ROOM-TEMPERATURE TENSILE-STRAINED NITI SHAPE-MEMORY ALLOY FIBER-REINFORCED 6082-ALUMINUM-MATRIX COMPOSITE

Macroscopic tensile and in-situ neutron diffraction measurements are r eported from a 20.5 volume percent, 50.7 at% Ni-Ti fiber reinforced 60 82-T6 aluminum matrix composite subjected to a room temperature, 4% te nsile elongation. The austenite B2(110) diffraction intensity was esse ntially stable until approximately 0.9% strain, beyond which, the aust enite B2(110) diffraction intensity strongly decreased with increasing tensile strain. The martensite M(001) diffraction intensity strongly increased from a zero intensity intercept at approximately 2.3% strain to the conclusion of tensile straining. This report concludes that th e initial decrease in austenite B2(110) diffraction intensity locates the initiation of stress induced transformations in the NiTi reinforce ment, furthermore this feature corresponds with an elevated yield poin t region in the macroscopic tensile results. Therefore, it appears tha t the elevated yield point region is caused by a temporary inhibition of fiber stress induced transformations.