| Abstract:The influence of homogenization annealing on ingot casting organization of Ti50Ni50-xCux alloys were studied, as well as the influence of Cu content, cold deformation, heat treatment, annealing temperatures and annealing time on microstructure and properties of Ti50Ni50-xCux alloys were studied by optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), conventional mechanical performance test, friction and wear test, internal friction test.The conclusions were as follows:(1) The as-cast organization of Ti50Ni50-xCux alloys exists serious segregation situation, such as rich Ti phase, the enrichment of Cu element in grain boundary. The matrix phase of alloys is TiNi0.8Cu0.2and the second phase like Ti2Ni and NiT also exist in the alloy. The size of the second phase Ti2Ni which contains rich Ti would decrease. And the phenomenon also occur in the boundary when refer to the enrichment of Cu element.(2) For solid solution state,25%+400℃/1h cold deformation annealed and cold deformation of35%+400℃/1h annealed state Ti5oNi45Cu5alloy, the microstructure are acicular martensite at room temperature. The grain sizes of alloys decrease, and the phase transformation temperatures also decreased in sequence. The martensite phase transformation process of alloy do not change at different annealing temperatures. The B2-B191phase transformation were happened when heating or cooling in the range of-50℃～150℃. For cold rolled state Ti50Ni50-xCux alloys, the phase transition characteristics temperatures were decrease after rising annealing temperature.(3)The tensile strength of Ti5oNi45Cu5alloy annealed at500℃/1h after25%cold deformation is918MPa and the elongation is13.4%, which satisfie the requirement of mechanical properties. And Ti50Ni45Cu5alloy in this state has the the highest recovery rate and wear resistance. In the meantime, the wear resistance of Ti50Ni50-xCux alloys increased with the increase of Cu contents.(4) The abrasion mechanism of Ti5oNi45Cu5alloy annealed in the process of friction and wear are:abrasive wear, adhesive wear and peeling wear. There are micro-cracks and wear pit in the wear surface, and there are granular and layered wear debris. The high wear resistance of Ti5oNi45Cu5alloy annealed due to the stress induced martensitic phase transformation and the rearrangement of martensite variant with the stress.(5) In the process of continuous variable temperature, the internal friction peak of Ti50Ni50-xCux alloys decrease when increase the vibration frequency and strain amplitude, but the peak position remains the same. At the same time, the internal friction peak and the peak position increase with the increase of the heating rate. The internal friction of alloys annealed after cold deformation are higher than alloy in solid solution state. The internal friction increased with the increase of annealing temperatures. |
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