Cast Intermetallic Alloys and Composites Based on Them by Combined Centrifugal Casting—SHS Process
This work aims to establish a scientific and engineering background in the production of cast multicomponent alloys and metalmartix composite (MMCs) via Self-Propagating High Temperature Synthesis (SHS, combustion synthesis) which is a novel process technique regarding fast and low-cost production ability. We carried out the search for reactive systems and process parameters that would ensure preparation of cast multicomponent materials in a single process. The principles and methods of the SHS thermite-type reaction processes have been investigated under high-gravity values applying loads up to 1000 g with special centrifuge set-up. In this way we expected to improve the yield of target product, remove gaseous byproducts, diminish the grain size in the product, and make product composition more uniform. The obtained results can be expected to make a theoretical background for industrial-scale manufacturing of heat-resistant intermetallic alloys, master alloys, catalysts, MMCs etc.
Production of cast electrodes from SHS-alloy based on NiAl in a metal shell, plasma rotating electrode process and getting composite microgranules for additive technologies
Implementing the latest additive technologies such as selective laser melting (SLM) and electron-beam melting (EBM), as well as direct metal laser sintering (DMLS) requires source materials (powders, or microgranules) of a specified chemical or granulometric composition. This paper describes a brand new technological process of obtaining composite microgranules that consists of three main stages: (1) synthesizing a NiAl-based intermetallic alloy of a specified chemical composition by centrifugal SHS metallurgy, (2) single-stage metallurgic processing (vacuum induction melting or inert-medium melting) of synthesized SHS materials (cast-charge materials, CCM) to be subsequently cast in a specially prepared steel tube for crystallizing; (3) centrifugal atomization (PREP) of the obtained steel-shell electrodes to make spherical composite microgranules. A NiAl-Cr-Co-Hf nickel-aluminide-based multi-component cast alloy was synthesized by that technology. We obtained the kinematic-viscosity dependency for this SHS alloy. Series of studies was conducted to optimize the vacuum-induction melting, and the melt was cast in a specially prepared steel crystallizer. We thus melted a double-layer electrode for plasma-rotating electrode process. The electrode was atomized to produce spherical microgranules and to study their morphology.
Submicron polymer structures with X-ray lithography and hot embossing
This article describes the process chain for replication of submicron structures with varying aspect ratios (AR) up to 6 in polymethylmethacrylate (PMMA) by hot embossing to show the capability of the entire LIGA process to fabricate structures with these dimensions. Therefore a 4.7 μm thick layer of MicroChem 950k PMMA A11 resist was spin-coated on a 2.3 μm Ti/TiOx membrane. It was patterned with X-ray lithography at the electron storage ring ANKA (2.5 GeV and λc ≈ 0.4 nm) at a dose of 4 kJ/cm3 using a Si3N4 membrane mask with 2 μm thick gold-absorbers. The samples were developed in GG/BDG and resulted in AR of 6–14. Subsequent nickel plating at 52°C resulted in a 200 μm thick nickel tool of 100 mm diameter, which was used to replicate slit-nozzles and columns in PMMA. Closely packed submicron cavities with AR 6 in the nickel shim were filled to 60% during hot embossing.