What is a memory alloy?

Memory alloy is a martensitic phase change alloy with regular atomic arrangement and less than 0.5% volume. The alloy is deformed by external forces. When the external force is eliminated, the original shape can be restored at a certain temperature. Because it has more than one million recovery functions, it is called a "memory alloy". Of course, it can't think and remember like the human brain, more accurately it should be called "memory shape alloy". In addition, memory alloys have the advantages of non-magnetic, abrasion resistance, corrosion resistance, and non-toxicity, so they have been widely used. Scientists have discovered dozens of alloys with different memory functions, such as titanium-nickel alloys, gold-cadmium alloys, and copper-zinc alloys.

Application of memory alloy:

Early applications include pipe joints, temperature control devices (such as temperature control traps), integrated circuit leads, automotive parts, etc.

Industrial applications:

(1) Unidirectional shape recovery uses unidirectional shape memory effect. Such as pipe joints, antennas, loops, etc.

(2) External bidirectional memory recovery. In other words, it uses the one-way shape memory effect and external force to perform repeated actions as the temperature rises and falls, such as thermal sensors, robots, and binding posts.

(3) Internal bidirectional memory recovery. In other words, the two-way memory effect is used to do repeated actions of temperature rise and fall, such as heat engine, thermal sensor, etc. However, this application has fast memory decay, poor reliability, and is not commonly used.

(4) Apply hyperelasticity. Such as springs, terminals, glasses frames, etc.

Medical applications:

Tini alloy has good biocompatibility, and there are many medical examples of its shape memory effect and superelasticity. Such as thrombus filters, spinal rods, orthodontic filaments, cerebral aneurysm clips, bone plates, intramedullary needles, artificial joints, contraceptives, heart repair components, artificial kidney micropumps, etc.

Prospects of high-tech applications:

The 20th century is an era of mechatronics. Sensor integrated circuit drive is the most typical mechatronic control system, but it is complicated and huge. The shape memory material has the dual functions of sensing and driving, which can realize the miniaturization and intelligence of control systems such as holographic robots and millimeter-level ultra-micro manipulators. The 21st century will be the era of materials electronics. Apart from temperature, the movement of the SMA robot is not affected by any environmental conditions. SMA robots are expected to play an important role in high-tech fields such as reactors, accelerators, and space laboratories.