Influence of processing conditions on strut structure and compressive properties of cellular lattice structures fabricated by selective laser melting

Abstract

a b s t r a c tAlSi10Mg cellular lattice structures have been fabricated by selective laser melting (SLM) using a range of laser scanning speeds and powers. The as-fabricated strut size, morphology and internal porosity were investigated using optical microscopy (OM), scanning electron microscopy (SEM) and X-ray microtomography (micro-CT) and correlated to the compressive properties of the structure. Strut diameter was found to increase monotonically with laser power while the porosity was largest at intermediate powers.Laser scanning speed was found to thicken the struts only at slow rates while the porosity was largest at intermediate speeds. High speed imaging showed the melt pool to be larger at high laser powers. Further the melt pool shape was found to vary cyclically over time, steadily growing before becoming increasingly instable and irregularly shaped before abruptly falling in size due to splashing of molten materials and the process repeating. Upon compressive loading, lattice deformation was homogeneous prior to the peak stress before falling sharply due to the creation of a (one strut wide) shear band at around 451 to the compression axis. The specific yield strength expressed as the yield stress/(yield stress of the aluminium  relative density) is not independent of processing conditions, suggesting that further improvements in properties can be achieved by process optimisation. Lattice struts failed near nodes by a mixture of ductile and brittle fracture.

Net-shape manufacturing using hybrid selective laser melting/hot isostatic pressing

“…The influence of laser process parameters and the build direction on the microstructure and the density of the SLM parts have been investigated by many workers. Parts made by SLM, show microstructural and mechanical properties different from those found in conventionally manufactured parts (Read et al, 2015, Qiu et al, 2015, Mumtaz and Hopkinson, 2009, Wong et al, 2007, Mumtaz and Hopkinson, 2010, Chantarapanich et al, 2014, Simhambhatla and Karunakaran, 2015, Li et al, 2016.…”

Processing of Al–12Si–TNM composites by selective laser melting and evaluation of compressive and wear properties

“…The SLM process offers a high degree of freedom and theoretically parts with any geometry (complex shapes and structures) and can be produced without restrictions, which are otherwise difficult or nearly impossible to produce using conventional manufacturing processes. [5][6][7][8] This process is also believed to lower the production time of complex parts, to maximize material utilization, and is considered to be environmentally friendly. 9 Most of the SLM research is focused on the following alloys: (i) pure iron, stainless steel, and different tool steel grades in the directions of parameter optimization, structure optimization, and evaluation of mechanical properties [10][11][12][13] ; (ii) Al-based alloys, like Al-12Si and AlSi10Mg, mainly focused on parameter optimization and evaluation of various properties [14][15][16] (iii) Ti6Al4V (for high strength aerospace applications), pure titanium and beta titanium alloys (bulk and porous scaffolds for bio-medical applications) focusing on the parameter optimization and evaluation of related bio-medical, corrosion and mechanical properties [17][18][19][20] ; (iv) Ni-based alloys like nitinol, inconels, and waspaloys (for high temperature properties and shape memory effects) mainly focused on parameter optimization and high temperature properties [21][22][23][24] and (v) Co-based alloys (CoCrMo as dental implants) focused on the microstructure and biomedical properties.…”

To enhance mechanical properties of parts produced from AlSi10Mg powder with use of SLS/SLM methods by densification of the product surface layer

“…Materiał ten charakteryzuje się wysoką przewodnością cieplną (ok. 200 W/m·K) i niewielkim ciężarem właściwym (2,67 g/cm 3 ). Jest to typowy stop odlewniczy o dobrej wytrzymałości i twardości, dzięki czemu może być stosowany do wykonywania podzespołów mechanicznych przenoszących duże obciążenia.…”

“…W związku z małą gę-stością (ok. 2,7 g/cm 3 ), dobrą przewodnością cieplną oraz relatywnie dobrą obrabialnością (a zwłaszcza spawalnością) stopy Al-Si z powodzeniem wykorzystuje się m.in. w przemyśle: narzędziowym (wkładki formujące z konformalnymi kanałami chłodzącymi) [1, 2], elektronicznym i maszynowym (radiatory oraz wymienniki ciepła), lotniczym (lekkie i wytrzymałe konstrukcje ażurowe) [3,4]. Ze względu na rosnącą popularność materiałów na bazie Al-Si stopy te coraz częściej wykorzystuje się podczas wytwarzania elementów metodami przyrostowymi (takimi jak selektywne spiekanie/topienie laserowe -SLS/SLM).…”