Nickel-titanium shape memory alloy sheet with gradient grain structure

Abstract

The invention provides a nickel-titanium shape memory alloy sheet with a gradient grain structure. A sheath is used for rolling deformation, and pressure stress is applied to the rolled plane of the nickel-titanium shape memory alloy sheet in the rolling process by means of a sheathed sheet; initiation and propagation of cracks in the rolling deformation process are restrained, so that sufficientplastic strain is accumulated at the surface layer and middle layer of the nickel-titanium shape memory alloy sheet synchronously; then, continuous bending deformation is performed, and the plastic strain distribution differentiation of the surface layer and middle layer of the sheet is achieved; finally, nanometer-sized grains are formed on the surface of the prepared nickel-titanium shape memoryalloy sheet through recrystallization annealing treatment, while micrometer-sized grains are formed at the middle layer of the sheet; and the production cost of the nickel-titanium shape memory alloysheet can be reduced obviously, and high-temperature oxidation of the sheet is avoided.

Description

technical field [0001] The invention belongs to the technical field of alloy materials, in particular to nickel-titanium shape memory alloy materials. Background technique [0002] As a functional material, nickel-titanium shape memory alloy has a shape memory effect, that is, nickel-titanium shape memory alloy is in a certain shape in the austenite phase and cooled to the martensitic transformation start temperature ( M s ) to begin to transform into twinned martensite, deform the nickel-titanium shape memory alloy in the martensitic phase state, and then heat it to the austenite transformation initiation temperature ( A s ) above, austenite transformation begins to occur, when the temperature rises to the end temperature of austenite transformation ( A f ) above, the nickel-titanium shape memory alloy will completely recover to the original shape of the austenite phase. [0003] Due to the shape memory effect of nickel-titanium shape memory alloy, it has been widely u...

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Problems solved by technology

Nanoscale grain size NiTi shape memory alloys have good biocompatibility but correspondingly poor shape memory, study shows

NiTi shape memory alloy with micron grain size has good shape memory effect but poor biocompatibility

[0004] At present, the preparation of nickel-titanium shape memory alloy bone plates is mostly based on nickel-titanium shape memory alloy plates, but these are plates with a single grain size, because the widely used plate processing methods (synchronous rolling, asynchronous rolling and Angle rolling, etc.) can only achieve the preparation of a single grain size plate, but cannot prepare a nickel-titanium shape memory alloy plate with a gradient grain structure with nano-sized grains on the surface and micron-sized grains in the middle layer

In addition, due to the high deformation resistance of nickel-titanium shape memory alloys at lower temperatures, significant strain hardening, and low plasticity, the processing and preparation of nickel-titanium shape memory alloy sheets is mostly carried out under medium-high temperature conditions. The multiple heating treatments of the plate have the problem of high temperature oxidation of the plate, and the production cost is high

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