An Effective Strengthening Strategy of Nano Carbide Precipitation and Cellular Microstructure Refinement in a Superalloy Fabricated by Selective Laser Melting Process

An effective strategy to strengthen a superalloy processed by selective laser melting (SLM) is proposed. The aim is to increase the yield strength of Inconel 718 fabricated by SLM to beyond 1400 MPa, which has never been achieved before. In this study, various NbC additions (0.0%, 0.5%, 1.0%, and 5.0% by weight) were added in the powder bed of Inconel 718, and two types of post-SLM heat treatments were investigated, i.e., solution heat treated plus aging (STA) and direct aging (DA). With NbC addition, smaller depth of melt pool and finer dendritic cells were obtained. Both STA and DA promoted the precipitations of γ’ and γ”. STA eliminated the cellular dendrites and induced grain growth while DA retained the as-built cellular dendrites, grain size, and nano-carbide from NbC addition, rendering a significant 326.2 MPa increase in yield strength. In this work, 0.5% NbC addition exhibited a record-high yield strength of 1461 MPa and ultimate tensile strength of 1575 MPa for Inconel 718 processed by laser manufacturing process according to literature data to-date.

Ultrafast laser manufacturing of nanofluidic systems

In the last decades, research and development of microfluidics have made extraordinary progress, since they have revolutionized the biological and chemical fields as a backbone of lab-on-a-chip systems. Further advancement pushes to miniaturize the architectures to nanoscale in terms of both the sizes and the fluid dynamics for some specific applications including investigation of biological sub-cellular aspects and chemical analysis with much improved detection limits. In particular, nano-scale channels offer new opportunities for tests at single cell or even molecular levels. Thus, nanofluidics, which is a microfluidic system involving channels with nanometer dimensions typically smaller than several hundred nm, has been proposed as an ideal platform for investigating fundamental molecular events at the cell-extracellular milieu interface, biological sensing, and more recently for studying cancer cell migration in a space much narrower than the cell size. In addition, nanofluidics can be used for sample manipulation in analytical chemistry, such as sample injections, separation, purifications or for quantitative and qualitative determinations. Among the nanofabrication technologies, ultrafast laser manufacturing is a promising tool for fabrication of nanofluidics due to its flexibility, versatility, high fabrication resolution and three dimensional (3D) fabrication capability. In this paper, we review the technological advancements of nanofluidic systems, with emphasis on fabrication methods, in particular ultrafast laser manufacturing. We present the challenges for issues concerning channel sizes and fluid dynamics, and introduce the applications in physics, biology, chemistry and engineering with future prospects.

Experimental investigation on the effect of platform heating on the dynamic mechanical properties of selective laser manufacturing of AlSi10Mg alloy

Additive manufacturing (AM) is one of the emerging promising technology technologies of manufacturing prototypes. The process of AM is based on melting powder by an energetic beam layer by layer to create a three-dimensional body. One of the lightweight alloys that is being used for AM is AlSi10Mg. The process of manufacturing is controlled by several tens of parameters most of which are determined by the machine manufacturer. One of the important parameters is the building platform temperature. In the present study we took samples from different heights of the building platform and measured the dynamic mechanical properties of each sample. It was noted that after a stress relief treatment (SRT) the difference in the static and dynamic mechanical properties along the building direction changed differently. The dynamic mechanical properties of samples that were fabricated in proximity to the building platform did not change after the SRT, while the mechanical properties of the samples that were fabricated far from the platform changed dramatically and became like those that were fabricated near the building plate.