Microstructure and mechanical properties of Al-12Si and Al-3.5Cu-1.5Mg-1Si bimetal fabricated by selective laser melting

An Al-12 Si/Al-3.5 Cu-1.5 Mg-1 Si bimetal with a good interface was successfully produced by selective laser melting(SLM). The SLM bimetal exhibits four successive zones along the building direction: an Al-12 Si zone, an interfacial zone, a texture-strengthening zone and an Al-Cu-Mg-Si zone. The interfacial zone(< 0.2 mm thick) displays an increasing size of the cells composed of eutectic Al-Si and a discontinuous cellular microstructure, resulting in the lowest hardness of the four zones. The texturestrengthening zone(around 0.3 mm thick) shows a remarkable variation of the hardness and <001>fiber texture. Electron backscatter diffraction analysis shows that the grains grow gradually from the interfacial zone to the Al-Cu-Mg-Si zone along the building direction. Additionally, a strong <001> fiber texture develops at the Al-Cu-Mg-Si side of the interfacial zone and disappears gradually along the building direction. The bimetal exhibits a room temperature yield strength of 267 ± 10 MPa and an ultimate tensile strength of 369 ± 15 MPa with elongation of 2.6 ± 0.1%, revealing the potential of selective laser melting in manufacturing dissimilar materials.