Papers by Keyword: Ferrous Alloys

Abstract: Post impact microstructural characteristics of 7.62 armour pearcing incendiary bullet was studied on AISI 4340 multilayerd welded joints. The potential application of AISI 4340 steel is found in the construction of combat vehicles using welding process. The welded joints are expected to offer better ballistic resistance like unwelded parent metals in combat vehicles. The traditionally used austenitic stainless steel welding consumables and the transformation effects of the welding process result in inferior ballistic performance of AISI 4340 steel welded joints. Published information revealed that a few attempts were made to successfully resist the bullets at multi layered weld metals by depositing a hard-facing interlayer between traditionally used austenitic stainless steel filler metals and a austenitic stainless steel buttering layer in between the parent metal and the hard – facing interlayer. This paper reports the pre-impact and post-impact microstructural characteristics of multi layered sandwiched joints made of a austenitic stainless steel root, a chromium carbide hard – facing middle layer and a low hydrogen ferritic capping front layer. The effect of the low hydrogen ferritic front layer on the ballistic performance after impact is studied in detail.

Abstract: Traditionally, the discovery of new materials has been the result of a trial and error process. This has resulted in an extremely time-consuming and expensive process. Models for guiding the discovery of new materials have been developed within the European Accelerated Metallurgy project. The application of statistical techniques to large materials datasets has lead to the discovery of unexpected regularities among their properties. This work focuses on mechanical properties. In particular, the interplay between yield strength, ultimate tensile strength and elongation. A methodology based on principal component analysis, and Kocks-Mecking modelling has led to a tool for finding optimal compositional and heat treatment scenarios. The model is first presented for wide ranges of alloys, and the application to the discovery of new magnesium and ferrous alloys is outlined.

Abstract: The use of a specially designed hypoeutectic cast iron as a potential raw material for the thixoforming process is described in this paper. Thixoforming technology normally uses aluminum-silicon alloys such A356 and A357 as raw materials. Iron-based alloys are less common, despite the lower cost of the raw material. The paper describes the semi-solid behavior and corresponding final microstructure of a hypoeutectic gray cast iron after thixoforming tests. The Fe-2.6wt%C-1.5wt%Si alloy was prepared via conventional casting in sand molds. Samples were heated to the semi-solid state at 1160 and 1180oC and held at these temperatures for 0, 30, 90 and 120s, and then subjected to compression tests. Two-platen compression tests were carried out in an instrumented eccentric press in order to determine the semi-solid behavior. The holding time in the semi-solid range simulates the industrial heating process that is time-controlled rather than temperature-controlled. The semi-solid behavior indicated that the semi-solid cast iron behaves like aluminum-silicon alloys, presenting a stress of up to 24MPa under 80% strain and a corresponding apparent viscosity of up to 1.5*105 Pa.s at 1180oC. The final microstructure after compression testing was essential in determining the material’s morphological evolution. Tests revealed that heating up to the semi-solid range followed by thixoforming changes the material’s graphite morphology from type A to B (or E), but does not significantly affect the interdendritic arm spacing between graphite lamellae. The resulting structure is composed of fine graphite and pearlite.

Abstract: The formidable and multivariate coal-mining conditions during the production often lead to various improper damage and inactivation of guide foot. Wear is the most severe problem. We do the research on optimization design of the materials by plasma cladding technic to improve the wear resistance: The Cr28MnV ferrous alloy overlay was deposited on the surface of 45# tempered steel backing. The martensitic structure with high strength, high hardness, and high abradability evenly distributed alloy carbide can be gained after cooling the overlay. The combined backing has a good obdurability which can satisfy the requirement of coal mine complex conditions after modifying treatment.

Abstract: The quantitative relationships are suggested that the applied stress decreases the nucleation barrier and activation energy of nucleation of martensitic transformation, and strain increases the nucleus sites. Taking Fe-20Ni-0.5C and Fe-25Ni-0.66C alloys as examples, their different martensitic morphologies in thermal-mechanical processing can be explained and the origin of such a difference may be revealed based on the above theoretical analysis. Accordingly, the control of martensitic morphologies in thermal-mechanical processing of ferrous alloys will become possible.