What is memory metal???
Memory metal is an alloy that can be arbitrarily shaped at lower temperatures and then heated back to its original shape, possessing memory properties. Therefore, we call it a "memory metal".
Memory metal, bend a straight iron wire into a right angle (90 °), and once released, it will recover a bit, forming an angle greater than 90 °. To straighten a bent iron wire, it must be folded over 180 degrees before releasing it, so that it can return to the straight state exactly.
For example, the crystal structure of nickel titanium alloy is different between above 40 ℃ and below 40 ℃, but when the temperature changes above or below 40 ℃, the alloy will shrink or expand, causing its morphology to change. Here, 40 ℃ is the "abnormal temperature" of nickel titanium memory alloy. Various alloys have their own abnormal temperatures.
The abnormal temperature of the high-temperature alloy mentioned above is very high. At high temperatures, it is made into a spiral shape and remains in a stable state. When it is forcibly straightened at room temperature, it is in an unstable state. Therefore, as long as it is heated to the abnormal temperature, it immediately returns to its original stable spiral shape.
