1.2　Motivation

In the past two decades，the components used in AM technology have gained significant technological advantages. Reliable industrial lasers with lower costs，cheap and high-performance computing hardware and software，and metal powder material technology have made them the most advanced processing. The reliability of the method has now reached a very high level of acceptance，as evidenced by the rapid growth of commercial system sales. AM metal processing technology developed in national laboratories，universities and industrial research laboratories.Although some applications have reached the technical readiness for fully certified production，it is necessary to have a more thorough understanding of raw materials，processes，structures，and properties to produce defect-free，reasonable and reliable AM components.