STRESS-INDUCED R-]B2 TRANSFORMATION AND PSEUDOELASTICITY ASSOCIATED WITH TWINNING IN A TI-NI ALLOY INCLUDING ALIGNED PARTICLES OF TI3NI4

A Ti-51 at%Ni alloy including aligned particles of Ti3Ni4 precipitate formed by aging under an applied stress exhibits an anomalous transfor mation, i.e., stress induced R(martensite)-->B2(parent) transformation . Confirmation of this transformation was made by tensile tests combin ed with simultaneous resistance measurements. This alloy also exhibits pseudoelasticity associated with twinning when tensile test is made a t a temperature sufficiently below its transformation temperature, i.e ., in the R-phase slate. The stress induced R-->B2 transformation and the pseudoelasticity in the R-phase state are due to the internal stre ss field formed by the aligned particles of Ti3Ni4.