JPS6247445A - Pseudoelastic alloy - Google Patents

Abstract

PURPOSE:To obtain superior pseudoelastic characteristic and further to provide the above characteristic even at the temp. below zero by substituting Ru for a specific portion of Ni in a TiNi alloy containing specific amounts of Ni. CONSTITUTION:In the TiNi alloy consisting of 51-52at% and the balance Ti, 0.5-2% Ru is substituted for a part of Ni. When this alloy is used for making springs, they provide perfect pseudoelastic characteristic at the temp. below zero.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a pseudoelastic alloy, and particularly to a pseudoelastic spring made of a TiNiRu alloy.

(Prior Art) It has been known that rT1Ni alloy exhibits a remarkable shape memory effect accompanying the reverse transformation of thermoelastic martensitic transformation, and it is also known that it also exhibits a so-called pseudoelastic effect. There is.

By the way, the pseudoelastic effect means that when a stress load is applied at a temperature higher than the reverse transformation completion temperature (hereinafter abbreviated as Af) of piNi alloy, 2. The martensitic phase is induced, causing an apparent plastic deformation of several to 10%, but upon unloading, the stress-induced martensitic phase returns to the parent phase and the shape is completely restored. It is the property of returning.

T1Ni alloy has excellent biocompatibility, is easier to deform than conventional wire, and is easy to attach to the human body due to the above-mentioned pseudoelastic effect, so it has recently been used for medical purposes. It is attracting attention as a spring material for straightening wires, catheters, etc.

Currently, piano wire,
Helical coil panel made of stainless steel wire etc. is used. The functions required of catheter guidewires are torque transmittance and flexibility at temperatures close to body temperature (35° C. in the evening). Furthermore, since the catheter is inserted into a blood vessel, it is required to exhibit a straight line within a range of at least 1 to 1.5 m.

By the way, special A9-20291 'l ~ culm old iyo T1N
It has been shown that the i-alloy wire satisfies the functions required for the above-mentioned catheter in the temperature range of 0°C to 40°C and can be used as a guidewire. Generally, the guide wire of a catheter is used at body temperature (z35° C.), so the above-mentioned 'piNi alloy also satisfies its function.

(Problem to be solved by the invention) On the other hand, it is not possible to immerse the guide wire in physiological saline cooled to below 0°C. It is difficult to obtain perfect pseudoelastic properties below ℃, therefore, 'I! i
Ni alloy does not satisfy the functions required for the above-mentioned guide wire and is not suitable for use.

Therefore, in an atmosphere below 0°C (refrigerator, etc.).

T1Ni alloy cannot be used as a spring material.

The object of the present invention is to provide a spring made of a pseudoelastic alloy that has perfect pseudoelastic properties at temperatures below 0°C.

(Means for Solving the Problem) The present invention provides a TiNi alloy consisting of 51 to 52 at% Ni and the remainder Ti, in which a portion of the Ni is replaced by 0.5 to 52 at% Ru.
It is a pseudoelastic alloy characterized by 2 at% substitution.

The composition of the pseudoelastic alloy according to the present invention is expressed by the following formula.

This is the following circular.

Ti,. . -xNiX-yRuy However, 51≦X≦52 0.5≦y≦2.0 (Example> The present invention will be explained below using examples.

TiN shown in the table below obtained by high frequency vacuum melting
After each iRu alloy was homogenized at a temperature of 900°C for 2 hours, it was shaped into diameters of 9mm by hot hammer and hot roll.
Processed to 5 m. Thereafter, intermediate annealing is performed at a temperature of 700 to 800°C, cold working is performed to a diameter of 1.3 mm, and then the diameter is 1.3 mm without annealing. The wire was cold-worked to Ottm (working rate: 40%) to obtain a wire.

The strands obtained as described above were heat treated at a temperature of 400° C. for 30 minutes to obtain alloy wire 2. One of these obtained alloy wires, a Ti49Ni50.5R"0.5 alloy wire (alloy wire with the composition of alloy number 2 shown in the table above), was subjected to temperature changes to examine the relationship between stress and strain. The results are shown in Figure 1 (,).
~V) is shown in the stress-strain diagram. Figures 1(a) to (4)
As shown in Figure 2, the Ti49" 50.5RuO,5 alloy wire exhibits a shape memory effect at temperatures below -21°C, but on the other hand, at temperatures above -12°C, it exhibits a complete pseudoelastic effect (Ti The relationship between stress and strain was investigated by varying the temperature of the alloy wire (with the composition of -51 at% Ni + alloy number shown in the table above).The results are shown in Figure 2 (a) -
Shown in (f). ′ which is clear from Figure 2 (,) to (f)
Thus, the r T 14yNi s1 alloy wire exhibits almost complete pseudoelasticity only after the temperature exceeds 14° C. (ie, exceeds 10° C.).

Figures 3 (,) and (b) show the relationship between the residual strain (chi) and temperature (°C) after loading and unloading of alloy wires (alloy numbers 1 to 5) having the composition shown in the above table, respectively, and the yield. Stress (kg/W
The relationship between m2) and temperature C°C is shown.

As is clear from FIGS. 3(a) and (b), the alloy wire containing 0.25 at % Ru (alloy wire A3) has only a small effect of adding Ru, and cannot obtain a pseudoelastic effect. Further, in the case of an alloy wire in which the total amount of Ni and Ru is 51 at% or less, pseudoelastic properties cannot be obtained at a temperature of 0° C. or less.

The total amount of Ni and Ru is up to 52 at% due to Ni.
+Ru) 52 at% alloy has difficulty in workability.

On the other hand, the reason why the Ru addition range is limited to 0.5 to 2.0 at% is because the effect of Ru addition is poor if it is less than 0.5 at%.
Even if it is added in excess of 2 at%, it is difficult to notice any significant addition effect.

Considering that Ru is expensive, the upper limit is set to 2. Oat% closed.

In this way, the above-mentioned pseudoelastic alloy has a higher deformation stress (yield stress) than the T1Ni alloy, and also has pseudoelastic properties even at temperatures below 0°C. It can be expected to be used as a spring material at low temperatures.

(Effects of the Invention) As explained above, the two pseudoelastic alloys according to the present invention exhibit good pseudoelastic properties at room temperature like the T1Ni alloy, and also exhibit good pseudoelastic properties at temperatures below 0°C. effective.

[Brief explanation of the drawing]

Figure 1 (,) to (1) are each T'49N' 50
．． Stress-strain diagram showing the relationship between stress and strain for 5RuO, 5 alloy wire at a constant temperature, Figure 2 (,) ~ (f
) is a stress-strain diagram showing the relationship between stress and strain for a Ti-51at%Ni alloy wire at a constant temperature, Figure 3 (
, ) and (b) are diagrams showing the temperature dependence of residual strain and yield stress of alloy wires having the compositions shown in the table, respectively. Agent (7783) Patent Attorney Noriyasu Ikeda Elongation (1%) 1-layer (%) V4 shape stress (Kg/'mm2) Residual strain (%)

Claims (1)

[Claims] 1. In a TiNi alloy consisting of Ni at 51-52 atomic concentration (at%) and the balance being Ti, 0.5-52 of the Ni
A pseudoelastic alloy characterized in that 2.0 atomic concentration (at%) is replaced with Ru.