1.1　Background

Additive Manufacturing （AM） technology，commonly known as 3D printing，refers to the manufacture of a wide range of geometrically complex geometric parts through the obtained three-dimensional model data. This process involves printing successive layers of material，which need to be formed layer by layer. This technology was developed by Charles Hull in 1986 in a process known as stereolithography. Subsequent developments included powder bed fusion，fused deposition modeling，inkjet printing，and contouring. AM involves a variety of methods，materials and equipments After years of development，it has already had a huge impact on manufacturing and logistics processes. AM has been widely used in different industries such as construction，prototype manufacturing and biomechanics.Due to the advantages of reducing waste，freedom of design and automation，this technology is widely used in aerospace，medical and automotive industries.

Metal additive manufacturing is a process that combines powder metallurgy，solidification，CAD/CAM（Computer Aided Design/Computer Aided Manufacturing），rapid prototyping and other technologies and builds layer by layer. Common metal additive manufacturing technologies include Selective Laser Sintering（SLS），Laser Metal Deposition（LMD），Laser-based Powder Bed Fusion （L-PBF），Electron Beam Melting（EBM），Laser Cladding，Direct Energy Deposition（DED），etc. These processes use thermal energy to melt a polymer，metal，or ceramic material，and these molten materials are deposited and solidified into the desired shape.