【Haichuan Teahouse】In space, what happens if two pieces of the same type of metal come into contact?
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In space, if two pieces of the same type of metal come into contact with each other, they tend to stick together quite easily. This phenomenon occurs due to cold welding between the metals. Most of the welding methods we see in everyday life involve using high temperatures to melt metal; once the melted metal solidifies, it fuses together, thus achieving welding – methods such as electric welding, gas welding, and friction welding. Cold welding can be carried out at room temperature, which is what gives it its name “cold”.
So how are two metal plates in full contact welded together? This is mainly due to the diffusion of metal atoms. When it comes to diffusion, we quickly think of gases and liquids, as these two types of substances are fluids, and it is easy to observe the diffusion of such substances in everyday life. In fact, diffusion also occurs in solids, only it is not as noticeable as in gases and liquids, so it is difficult for us to observe. In a vacuum, atoms between two metals in full contact diffuse into each other and merge, thereby forming new metal bonds that cause the two metals to be \"welded\" together. Some scientists have specifically studied the phenomenon of cold welding, using nanogold wires in a vacuum environment; they found that it takes only about two minutes for the two nanowires to stick together.
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