Huizhou Pengchengrui Technology Co., Ltd.

Nickel titanium alloy can be easily kneaded, but stainless steel is very hard?

Core reason: Nickel titanium is a shape memory alloy that undergoes martensitic transformation deformation; Ordinary stainless steel undergoes slip plastic deformation, and the deformation mechanisms of the two are completely different.

1. Nickel titanium alloy (titanium nickel): phase transformation deformation, like plasticine

Nickel titanium alloy exhibits martensitic phase at low temperatures:

When external forces come, they do not directly pull and displace metal atoms, but instead cause twinning rearrangement inside the crystal. The crystal only undergoes a "flip and rearrangement" of its internal structure, without a large number of atomic bonds breaking or being displaced.

>Performance: It can be bent, kneaded and twisted into Fried Dough Twists by a large margin. After the external force is removed, the crystal will return to its original shape as long as it is heated (or heated).

⚠️ Attention: It is not made arbitrarily without limit. If the bending angle is too large or repeatedly bent beyond the limit, nickel titanium will also break, but the allowable deformation is much greater than that of stainless steel.

Deformation amount: Nickel titanium martensite can achieve reversible deformation of 8% -10%.

Nickel-titanium alloy tube

2. Stainless steel: ordinary plastic deformation, easily damaged by hard bending

Stainless steel (304/316) does not have this phase transition mechanism.

When bending, it can only rely on dislocation sliding: atomic layers in the crystal move and slide against each other.

-Small angle bending: can bounce back (elastic deformation)

-Bend a little bigger: Atoms undergo permanent displacement, resulting in plastic deformation. Once bent, they will bend and will not bounce back on their own;

-Continuing to fold violently: a large number of dislocations accumulate, causing cracks and direct fracture.

The reversible elastic deformation of ordinary stainless steel is only about 0.2%, and it will permanently deform when bent slightly, and then break when folded back.

Simple and popular analogy

-Nickel titanium martensite: like a stack of playing cards, external force only tilts and positions the cards as a whole. Removing the external force, when heated, the playing cards automatically straighten out. The deformation is significant and the damage is minimal.

-Stainless steel: like a stack of hard paper, it can bounce back even when bent a little bit; If the bend is too large, the paper will fold with creases (dislocation damage), and if it is folded a few more times, it will tear directly.

Supplement small knowledge points

1. Nickel titanium is not soft in any state: when the temperature is above the phase transition point, it becomes austenitic and is also very hard, similar to ordinary spring steel, and cannot be kneaded casually. We see nickel titanium wire that can be kneaded and is in a martensitic state.

2. Medical stents and orthodontic archwires are made of nickel titanium: they return to their predetermined shape at body temperature; The surgical knife and catheter sheath are made of stainless steel, which has high strength but cannot be bent at large angles.

Not all nickel and titanium can remember, as their composition and heat treatment determine the phase transition temperature.

one-sentence summary

>Nickel titanium achieves large deformation through twinning phase transition within the crystal; Stainless steel can only slide by atomic displacement, and even slight deformation can leave permanent damage, so stainless steel cannot be kneaded arbitrarily.

Huizhou Pengchengrui Technology Co., Ltd. specializes in producing high-performance nickel titanium alloy pipes. The pipe material has excellent superelasticity and shape memory performance, can be repeatedly bent and kneaded to restore its original shape, and has good corrosion resistance and biocompatibility. Precision cold rolling process, high dimensional accuracy, complete specifications, supports customization according to demand. Widely used in medical intervention, aerospace, intelligent equipment and other fields, it controls the entire process from raw materials to finished products, providing customers with stable and reliable nickel titanium pipe solutions.