Date of Award

8-29-2018

Degree Type

Thesis

Degree Name

M.Sc.

Department

Mechanical, Automotive, and Materials Engineering

First Advisor

Green, Daniel

Rights

CC-BY-NC-ND

Abstract

Extensive research has been carried out in the field of additive manufacturing technologies to characterize the mechanical properties of various alloys, but only a limited understanding of the effects of different process parameters and of ex-situ post processes has been gained so far, limiting the robustness of the designs, as the process can be characterized by a significant variability of the results. Data in the literature show how the performance of additively manufactured parts can be improved by ex-situ heat treatments which reduce defects and residual stresses in the part, yielding properties comparable with those of cast or wrought materials. The present study is aimed at providing the characterization of the mechanical properties of the AlSi10Mg alloy manufactured with Selective Laser Melting (SLM), comparing the effects of different process parameters and of a post-process stressrelieving heat treatment on the final mechanical properties of the material. The printed specimens were subject to an array of examinations including chemistry, density, hardness and tensile tests. An inspection of the fractured surfaces with a Scanning Electron Microscope (SEM) was also carried out to better understand the test results. The experiments showed that SLM-manufactured parts can achieve mechanical properties comparable with those of traditional cast parts, however the parts present a marked anisotropy depending on the build direction, with elongation being up to 43.2% lower in specimens grown along the Z-axis compared to those grown on the XY-plane. A reduction in anisotropy, together with a minimum increase of 80% in elongation was achieved after stress-relieving. Fractographic analysis showed a ductile intergranular fracture surface, but it also highlighted how tensile results are highly influenced by internal defects.

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