Nitinol alloy is a shape memory alloy. Shape memory alloy is a special alloy that can automatically restore its plastic deformation to its original shape at a certain temperature. Its expansion rate is more than 20%, 1*10 power of 7, damping characteristics are 10 times higher than ordinary spring, its corrosion resistance is better than the current good medical stainless steel, so it can meet all kinds of engineering and medical application needs, is an excellent functional material. In addition to the shape memory function, memory alloy also has the excellent characteristics of wear resistance, corrosion, high damping and high elasticity.