Which process involves injecting metal into a mold under high pressure?

The process that involves injecting metal into a mold under high pressure is die casting. This method is specifically designed for creating metal parts with high precision and intricate shapes. In die casting, molten metal is forced into a mold cavity, typically made of steel, which allows for fast production rates and excellent surface finishes. The high pressure ensures that the molten metal fills all areas of the mold quickly and completely, reducing the likelihood of defects such as air pockets or incomplete fills.

Die casting is particularly effective for producing complex parts with tight tolerances and smooth surfaces, making it a popular choice in industries such as automotive and consumer electronics. The use of high pressure differentiates die casting from other metal forming processes, which may utilize gravity or lower pressures to shape the metal. This is why die casting is the correct answer in this context.