Microstructure and mechanical properties of aluminium alloy cellular lattice structures manufactured by direct metal laser sintering

Abstract This study thoroughly investigated the microstructure and mechanical properties of AlSi10Mg periodic cellular lattice structures with a wide range of volume fractions (5–20%) and unit cell sizes (3–7 mm) fabricated via direct metal laser sintering (DMLS). It was found that the arc-shaped melt pools are overlapping with each other and comprising near fully dense struts (relative densities≥99%) of the as-built lattice structures. The melt pools of the struts are characterized with very fine cellular-dendritic microstructure. Two distinctive zones in the melt pool can be distinguished: the boundary of melt pool possesses the coarse cellular/dendritic microstructure with the cell size or dendrite arm spacing ranging of 2–4 µm, while the interior of melt pool exhibits the much finer cellular microstructure consisting of the 400–700 nm cells mainly filled with the α-Al matrix and some embedded rod-type Si-phases, and the network boundaries predominantly generated by the aggregates of approximately 20 nm Si particles. Both compression strength and microhardness decrease with the increase in the unit cell size when the volume fraction is fixed. This is mainly because the thinner struts of the smaller unit cell size lattice structures were cooled faster by their surroundings and then exhibit a higher cooling rate, leading to finer microstructure. The compression strength increases with increasing the volume fraction, and an equation based on the Gibson–Ashby model is established to estimate the compression strength of DMLS-produced AlSi10Mg gyroid cellular lattice structures with the 3 mm unit cell size.

[1]  Y. Birol.  Microstructural evolution during annealing of a rapidly solidified Al–12Si alloy , 2007 .

[2]  J. Kruth,et al.  Fine-structured aluminium products with controllable texture by selective laser melting of pre-alloyed AlSi10Mg powder , 2013 .

[3]  J. Kruth,et al.  Micro-CT-based improvement of geometrical and mechanical controllability of selective laser melted Ti6Al4V porous structures , 2011 .

[4]  T. Nieh,et al.  Effect of Cell Size on the Dynamic Compressive Properties of Open-Celled Aluminum Foams , 2002 .

[5]  Ahmed Hussein,et al.  Evaluations of cellular lattice structures manufactured using selective laser melting , 2012 .

[6]  O. Uzun,et al.  Hardness and microstructural characteristics of rapidly solidified Al–8–16 wt.%Si alloys , 2004 .

[7]  M. Ashby,et al.  Cellular solids: Structure & properties , 1988 .

[8]  P. S. Leung,et al.  A novel method for manufacturing sintered aluminium heat pipes (SAHP) , 2013 .

[9]  K. Benyounis,et al.  Rapid solidification of M2 high-speed steel by laser melting , 2009 .

[10]  Eleonora Atzeni,et al.  From Powders to Dense Metal Parts: Characterization of a Commercial AlSiMg Alloy Processed through Direct Metal Laser Sintering , 2013, Materials.

[11]  M. Ashby,et al.  Metal Foams: A Design Guide , 2000 .

[12]  J. Kruth,et al.  Mechanical Properties of AlSi10Mg Produced by Selective Laser Melting , 2012 .

[13]  E. Brandl,et al.  Additive manufactured AlSi10Mg samples using Selective Laser Melting (SLM): Microstructure, high cycle fatigue, and fracture behavior , 2012 .

[14]  H. Maier,et al.  In situ characterization of the deformation and failure behavior of non-stochastic porous structures processed by selective laser melting , 2011 .

[15]  Jan Bültmann,et al.  High Power Selective Laser Melting (HP SLM) of Aluminum Parts , 2011 .

[16]  Wesley J. Cantwell,et al.  The quasi-static and blast loading response of lattice structures , 2008 .

[17]  M. Ashby,et al.  The topological design of multifunctional cellular metals , 2001 .

[18]  Lewis Mullen,et al.  Selective Laser Melting: a regular unit cell approach for the manufacture of porous, titanium, bone in-growth constructs, suitable for orthopedic applications. , 2009, Journal of biomedical materials research. Part B, Applied biomaterials.

[19]  J. Shang,et al.  Preparation of three-dimensional shaped aluminum alloy foam by two-step foaming , 2008 .

[20]  Liang Hao,et al.  Evaluation of light-weight AlSi10Mg periodic cellular lattice structures fabricated via direct metal laser sintering , 2014 .

[21]  Moataz M. Attallah,et al.  Microstructure and tensile properties of selectively laser-melted and of HIPed laser-melted Ti–6Al–4V , 2013 .

[22]  H. Wadley,et al.  Compressive behavior of age hardenable tetrahedral lattice truss structures made from aluminium , 2004, Acta Materialia.

[23]  Christopher J. Sutcliffe,et al.  Selective laser melting of aluminium components , 2011 .

[24]  Ryan B. Wicker,et al.  Characterization of Ti–6Al–4V open cellular foams fabricated by additive manufacturing using electron beam melting , 2010 .

[25]  L. Gibson,et al.  Size effects in ductile cellular solids. Part II : experimental results , 2001 .

[26]  Ryan B. Wicker,et al.  Open-cellular copper structures fabricated by additive manufacturing using electron beam melting , 2011 .

[27]  Konda Gokuldoss Prashanth,et al.  Microstructure and mechanical properties of Al-12Si produced by selective laser melting: Effect of heat treatment , 2014 .

[28]  Robert F. Singer,et al.  Processing of Metal Foams—Challenges and Opportunities , 2000 .

[29]  Zhihua Wang,et al.  Studies on the dynamic compressive properties of open-cell aluminum alloy foams , 2006 .

[30]  Christopher B. Williams,et al.  Additive manufacturing of metallic cellular materials via three-dimensional printing , 2011 .