Critical Temperature Range in Standard and Ni-bearing Spheroidal Graphite Cast Irons
Describing the conditions for reaustenitization of spheroidal graphite cast irons is of interest for their heat-treatment after casting, e.g. for manufacturing austempered ductile irons. Differential thermal analysis has been used to characterize the direct eutectoid transformation and the reverse transformation, i.e. the reaustenitization. This has been applied to a standard and a Ni-bearing alloy, with a ferritic matrix for the former, both a ferritic and a pearlitic matrix for the latter. The results are discussed in relation with the stable and metastable three phase fields. While earlier description of the direct eutectoid transformation is confirmed, the one for reverse eutectoid has been found more complex and is amended.
Solid state transformations in ductile iron—influence of prior austenite matrix microstructure
The decomposition of austenite after different cooling rates has been studied for unalloyed and alloyed ductile iron. The influence of the austenite microstructure was evaluated. Jominy like tests were carried out on samples shaken out from the mold at temperature below the eutectoid range, and on samples austenitized conventionally. The hot shaken out samples show greater hardenability than conventionally reheated samples. This is caused by the much larger grain size displayed by the austenite during the post-solidification cooling. The matrix microstructure was evaluated along the length of the Jominy samples. Different growth patterns of ferrite were identified. A continuous transformation diagram for ductile iron was proposed.
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.