Rapid production of AZ91 Mg alloy by extrusion based additive manufacturing process

ABSTRACT

AZ91 magnesium alloy parts were successfully produced using a novel extrusion-based additive manufacturing process. The green parts were built in two different orientations and subjected to debinding and sintering treatments. The as-built alloy showed a heterogeneous microstructure made up of α – Mg matrix, Al₈Mn₅ second phase particles, MgO layers and Mg₁₇Al₁₂continuous precipitates. After solution treatment followed by aging, Mg₁₇Al₁₂ discontinuous precipitates were observed. The sintered samples showed a yield strength and ultimate tensile strength of 79 and 207 MPa, respectively, in the horizontal configuration. Analysis of the fracture surfaces revealed that a continuous network of magnesium oxide layer around the powder particles act as preferential path for crack propagation.

KEYWORDS:

• Additive manufacturing
• magnesium
• AZ91
• microstructure
• DSC
• electron microscopy

Acknowledgements

The Helmholtz-Zentrum Geesthacht, where feedstock preparation, debinding and sintering was carried out by co-author J. Schaper, is highly acknowledged.The Italian Ministry of Education, University and Research is acknowledged for the support provided through the Project “Department of Excellence LIS4.0 - Lightweight and Smart Structures for Industry 4.0.”

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Notes on contributors

A.S. Vishwanath

A.S. Vishwanath completed M.Sc in Materials Engineering and Nanotechnology at Politecnico di Milano in 2020.

K. Rane

K. Rane received his master’s degree from College of Engineering Pune in 2011. He completed his doctorate in Mechanical Engineering from Indian Institute of Technology Bombay, Mumbai in the year 2015. Dr. Rane conducted post-doctoral research in modeling and optimization of advanced manufacturing processes for three years at Politecnico di Milano, Milan, Italy.

J. Schaper

J. Schaper studied Mechanical Engineering Flensburg University of Applied Sciences with his Master's thesis focusing on binder development for Metal Injection Moulding of Magnesium followed by his PHD in the same field of research. Since receiving his PHD in 2019 he is responsible at Element22 GmbH (Kiel, Germany) as Project Manager for additive manufacturing of Titanium using sinter based AM technologies.

M. Strano

Prof. M. Strano is associate professor at the Dipartimento di Meccanica, Politecnico di Milano since 2014. His research activities include the design and optimization of advanced manufacturing processes such as sheet metal forming, cryogenic machining, extrusion-based additive manufacturing, etc. He is the author of about 125 publications in the field of manufacturing systems and processes.

R. Casati

Prof. R. Casati is chair of the Metallurgy course for Materials Engineering and Nanotechnology students at the Politecnico di Milano. His research deals with the evolution of microstructure and mechanical behavior of metallic materials during manufacturing and service. In recent years, his scientific activity has focused on alloys and composite materials produced by powder metallurgy and additive manufacturing processes.