Investigation of material and mechanical properties of Al alloy and Al based MMC parts produced by DMLS for industrial application

Additive Manufacturing (AM) is the process of joining materials layer upon layer to produce parts from CAD model. Direct Metal Laser Sintering (DMLS) is an AM process in which metallic parts can be produced. The knowledge of material and mechanical properties are important for producing lightweight and functional parts. Hence, this thesis focuses on characterizing material and mechanical properties of a lightweight alloy processed by DMLS, and using it as metal matrix for producing composites in DMLS process. AlSi10Mg was selected as lightweight alloy and it is similar to an A360 cast alloy in chemical composition. The morphology and size distribution of the AlSi10Mg starting powder was investigated by using Field Emission Scanning Electron Microscope (FESEM) and laser granulometry, respectively. Chemical composition of the AlSi10Mg powder was analyzed by using Inductive Coupled Plasma test. Material characterization of AlSi10Mg specimen produced by DMLS was carried out by using optical microscope, FESEM and X-ray Diffraction technique (XRD). Thereafter, mechanical properties such as hardness, tensile strength and Charpy impact energy were evaluated. Effect of different post processing operations on mechanical properties of AlSi10Mg parts were also investigated. Due to the very fine microstructure of the AlSi10Mg parts produced by DMLS process, nanoindentation measurements were performed. Investigation of process parameters and their effect on final density and hardness of AlSi10Mg specimens based on Design of Experiments (DOE) approach was carried out. Regression analysis was also conducted. Effect of the heat treatment (e.g. precipitation hardening T6) on the AlSi10Mg parts was also investigated. Composite materials offer better properties comparing to traditional materials. The Metal Matrix Composite was produced by DMLS process. The matrix was of AlSi10Mg and 10 wt% SiC was used as ceramic reinforcement. The microstructure of the composite was studied by using optical microscopy and FESEM. Evaluation of mechanical properties of the composite specimens was carried out. Finally, the production of a complex shape lightweight structure by DMLS was studied.