Ni Alloy Wire Research Articles

Functional Properties of Nanostructured Ti-50.0 at % Ni Alloys

Abstract Ti-50 at % Ni alloy wire is subjected to cold-rolling (true strain e=0.3-1.9) and post-deformation annealing (200–700°C range). For all levels of cold work, the maxima of recovery strain and stress are obtained after annealing in the 350–400°C range. For the moderately-to-high cold-worked material (e=0.3-0.88), this annealing leads to polygonization, while for the severely cold-worked one (e=1.9), to the material nanocrystallization (grains of 50–80 nm in size). Nanocrystallized alloy generates 30 % higher recovery stresses (up to 1450 MPa) and 10% higher completely recoverable strains (more than 8 %) as compared to the polygonized alloy, while having comparable mechanical properties in tension.

K-0401 抵抗溶接されたTi-50.9at%Ni合金線材の形状記憶特性(S08-1 機能特性・変態)(S08 形状記憶合金の製造・加工技術と機能発現)

Since the resistance welding technique is widely applied for joining in several metals and alloys, this may be also applicable for Ti-Ni alloys. It is also known in Ni-rich Ti-Ni alloys that the shape memory and mechanical properties depend on heat-treatment through microstructural change. In this study, the resistance-welding was applied for Ti-50.9at%Ni alloy wires with 1mm in diameter. In order to clarify the effect of heat treatment, various heat treatments were performed before and after the resistance welding. Mechanical characteristics such as fracture stress and strain were investigated by tensile tests. The fatigue life was evaluated using rotary-bending fatigue tests. Microstructural observation for welded zone and heat affected zone (HAZ) was also carried out by optical microscope and transmission electron microscope (TEM). It was found that the fracture stress of some resistance-welded wires exceeded 1GPa. Optical microscope and TEM observation revealed that microstructure near welded zone was affected by heat treatment, resulting in change of mechanical properties.

A simple inductive contactless switch

When a small coil wound around a fine core of low coercivity square-loop Fe-6 wt. % Ni alloy wire is excited with a 100-kHz ac current it develops a peak voltage much greater than that obtained from a coreless coil. This effect can be used to sense motion of the core in and out of the coil or alternatively to sense motion of an external biasing magnet. Either way one has a position sensor which is extremely simple and which could be useful in a variety of applications, such as high-reliability keypad switches, proximity switches, and switches for use in hazardous or corrosive atmospheres.

Magnetic sensors using Fe-Cr-Ni alloys with square hysteresis loops

Voltage-generating magnetic sensors using new square-loop Fe-Cr-Ni magnetic alloy wires are described. Typical magnetic properties of the sensor wire are Br ∼15 kG, Br/Bs ∼0.99, and Hc ∼2–30 Oe. These alloys are corrosion resistant, easy to manufacture into desired wire shape and sensor geometry, and are of low material and processing cost. One exemplary sensor consists of an Fe-20%Cr-4%Ni alloy wire of 0.1–0.5 mm in diameter, 3.7 cm in length, and a sense coil of 1000–2000 turns wound around the alloy wire. With an external ac drive field of 20–200 Oe at various frequencies, voltage pulses with a peak amplitude in excess of 30 V are generated. This sensor may be used as a proximity/displacement sensor, current sensor, rotation/frequency sensor, and other triggering, switching, and security devices.