Microstructural evolution of NiTi shape memory alloy (SMA) with a nominal composition of Ni50.9Ti49.1 (at %) is investigated on the basis of heat treatment and severe plastic deformation (SPD). As for as-rolled NiTi SMA samples subjected to aging, plenty of R phases appear in the austenite matrix. In terms of as-rolled NiTi SMA samples undergoing solution treatment and aging, Ni4Ti3 precipitate...

Near-equiatomic Ni-Ti, known for its shape memory behavior, can decompose to martensitic phases and/or second phase compounds. This phase competition is investigated in NixTi100-x (49<x<55) in as-quenched (AQ) and shock-loaded states. Dynamic loading was done with direct drive laser pulses of nanosecond duration; shocked samples were recovered for analysis. Unexpectedly, the lowest-Ni alloy (x ...

Concentration gradients surrounding Ni4Ti3 precipitates grown by appropriate annealing in a Ni51Ti49 B2 austenite matrix are investigated by electron energy loss spectroscopy (EELS) and energy filtered transmission electron microscopy (EFTEM). Concentration gradients of approximately 1.0-2.0 at.% in Ni within the surrounding B2 matrix can be detected by both EELS and EFTEM, revealing a Ni deple...

Hydroxyapatite coatings were deposited for 1, 2, and 3 h on NiTi substrates using plasma-assisted radio frequency sputtering. The matrix consisted of B2 B19’ phases Ti2Ni, Ni3Ti, Ni4Ti3 intermetallic compounds. surface coating was monoclinic hydroxyapatite. Increasing the deposition time to made it possible form a dense hydroxyapatite layer without visible defects. phase contrast maps showed th...

NiTi shape memory alloy (SMA) has been widely used in many fields for its superelastic and behaviors. The compressive fatigue life of is very high, but the tensile bending relatively low. In this study, pre-strain laser shock peening (LSP) introduced to solve these challenges. Different heterogeneous nanostructured (containing B2, B19′ phases, precipitates including Ni3Ti Ni4Ti3) gradient resid...

The present study utilizes molecular dynamics simulations to the athermal and stress-induced martensitic transformation of B2 B19' phase in a Ni-Ti alloy effect precipitates on transformation. demonstrate existence an intermediate B19 between martensite austenite phases. Nickel-Titanium shape memory with is studied by introducing Ni3Ti, NiTi2 Ni4Ti3 individually using atomistic simulations. res...