The influence of rare earth (RE) elements on the microstructure and mechanical performance of an extruded ZK60 Mg alloy was studied. Two types of RE elements were added to a ZK60 material and then extruded at a ratio of 18:1. The first new alloy contained 2 wt% Y while the second one was produced using 2 wt% Ce-rich mischmetal. The microstructure, the texture, and the dislocation density in a base ZK60 alloy and two materials with RE additives were studied by scanning electron microscopy, electron backscattered diffraction, and X-ray line profile analysis, respectively. It was found that the addition of RE elements caused a finer grain size, the formation of new precipitates, and changes in the initial fiber texture. As a consequence, Y and Ce-rich RE elements increased the strength and reduced the ductility. The addition of these two types of RE elements to the ZK60 alloy decreased the work hardening capacity and the hardening exponent mainly due to grain refinement.

Copper (Cu) is a promising material to be used in applications that need high thermal or electrical conductivity, corrosion resistance, and formability. One of its essential disadvantages is low mechanical properties such as hardness, strength, and wear resistance. These issues are more important when a part is in contact with another part. To tackle these problems, it is attractive to make surface composites by using reinforcements such as ceramic particles or fibers. It is possible to use vast kinds of methods such as ultrasonic mechanical coating and laser cladding to fabricate surface coating. However, these methods are generally expensive and difficult to perform. Friction stir processing (FSP) is one of the novel and applicable methods to fabricate composites on the surface of different materials like Cu, Al, and Mg. FSP is a solid-state deformation technique that uses a non-consumable tool, and simultaneous effect of friction, heat, and loading plasticizes the material, and by mixing the base metal and reinforcement can make a composite. So far, numerous studies have been carried out on the microstructure and properties of Cu-surface composites produced by FSP. In the present paper, the effects of FSP parameters (for example, rotation speed, traverse speed, number of passes, tool profile), and reinforcement particles’ state (size, amount, type) on the microstructure, mechanical properties, wear resistance, corrosion behavior, friction coefficient, and conductivity of Cu-surface composites, as well as the grain refinement and hardening mechanisms are reviewed.