How are metal composite materials bonded together

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Metallic composite materials refer to composite materials formed by the metallurgical bonding of two or more different metals; common examples include titanium-steel composites, copper-steel composites, titanium-zinc composites, titanium-nickel composites, nickel-steel composites, copper-aluminum composites, and nickel-copper composites. Due to their ability to leverage the advantages of individual constituent materials, enable optimal allocation of these materials, save precious metal resources, and meet performance requirements that cannot be achieved with single metals, metal composite materials are being widely used in an increasing number of fields. When encountering metal composite materials for the first time, one is bound to have doubts: how are different metals \"bonded\" together? The common metal composite methods are as follows; let’s take a look. The explosion welding method utilizes **as an energy source, and through the high-speed detonation and shock waves generated by it, different metals are welded together over large areas. The rolling compounding method involves using the rolling force of a rolling mill to cause plastic deformation in the surfaces of the two metals that are to be combined. This leads to the cracking of the metal surfaces, and the fresh metal exposed at these cracks comes into contact with each other; under pressure, a metallurgical bond is formed between the metals. Based on the temperature during rolling, the rolling combination methods can be divided into hot rolling and cold rolling. ☆ The hot rolling compounding method involves using the rolling force of a rolling mill at a certain temperature to roll the metals to be compounded, thereby achieving a metallurgical bond. Hot-rolling compounding is the main method for producing composite sheets; it offers advantages such as simple processing procedures and high production efficiency. It also allows full utilization of the rolling capacity of the rolling mills as well as the plastic deformation capability of the materials at high temperatures, resulting in a high bonding strength at the metal-composite interface. ☆ Cold rolling compounding: Cold rolling compounding was developed on the basis of hot rolling compounding. Due to the lower temperature used in this process, it is possible to avoid phase transformations and microstructural changes in the metal materials that could hinder bonding, as well as the formation of brittle intermetallic compounds. Composites produced by cold rolling exhibit stable properties, and it is possible to achieve the rolling combination of various materials; however, the deformation rate of the matrix metal during the rolling process can reach 60%–70%. Explosion-rolling composite method: The explosion-rolling composite method involves using explosion bonding technology to weld two or more metal sheets that are to be combined together, in a proportion that ensures the desired thickness, thereby creating a composite slab. This slab is then hot-rolled or cold-rolled, depending on the specific conditions and requirements, to achieve the desired thickness for the final composite sheet. Powder metallurgy method: The powder metallurgy method involves spreading evenly mixed metal powders on the surface of a base metal and compressing them, followed by high-temperature sintering in a protective atmosphere. Finally, machining is carried out to produce the finished composite material. Diffusion bonding: Diffusion bonding involves bringing two metals into close contact and holding them at a certain temperature and pressure for a period of time, allowing the atoms at the interface to diffuse into each other and form a metallurgical bond. Centrifugal casting is a method in which molten alloy is poured into a rotating mold made of base metal. Under the effect of centrifugal force, the molten alloy adheres to the inner walls of the mold; after rapid cooling and solidification, it fuses tightly with the base metal. Casting composite method: The casting composite method involves subjecting the base metal to surface pretreatment and preheating it to a certain temperature, after which it is immersed in a casting mold cavity filled with the coating metal liquid; or the base metal is placed in the casting mold cavity and then the coating metal liquid is poured into it. Once the liquid metal solidifies and cools, a composite material is formed. Continuous casting-rolling composite method: This method combines the traditional casting process with the rolling process. High-temperature molten metal is continuously poured onto the surface of the base steel plate, allowing the liquid metal to be rolled simultaneously on the rolling mill while it is still in a semi-solid state, together with the solid base metal. The rolling force exerted by the mill, along with the high-temperature diffusion of the liquid metal, enables a metallurgical bond to form between the two metals.