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Full-Text Articles in Engineering

Identification And Characterization Of The Iron-Zinc Intermetallics Formed In Galvanneal Steel, Richard Frederick George Grant Apr 1995

Identification And Characterization Of The Iron-Zinc Intermetallics Formed In Galvanneal Steel, Richard Frederick George Grant

Physics Theses & Dissertations

The demand to improve the corrosion resistance of steel sheet, particularly for use within the automotive industry, has led to a dramatic increase in the use of coated steels in place of cold-rolled sheet steel. Galvanneal steel results from the post annealing of the zinc-coated steel sheet, in which iron and zinc are interdiffused to form an iron-zinc alloy coating. Within this alloy coating, four main iron-zinc phases, Zeta, Delta, Gamma-1, and Gamma may be present. Manufacture of the most suitable coating requires identifying which phases form during the galvannealing process, an understanding of the properties of each phase and ...


Stability Of A Eutectic Interface During Directional Solidification , Seung Hoon Han Jan 1995

Stability Of A Eutectic Interface During Directional Solidification , Seung Hoon Han

Retrospective Theses and Dissertations

Directional solidification of eutectic alloys shows different types of eutectic morphologies. These include lamellar, rod, oscillating and tilting modes. The growth of these morphologies occurs with a macroscopically planar interface. However, under certain conditions, the planar eutectic front becomes unstable and gives rise to a cellular or a dendritic structure. This instability leads to the cellular/dendritic structure of either a primary phase or a two-phase structure. The objective of this work is to develop a fundamental understanding of the instability of eutectic structure into cellular/dendritic structures of a single phase and of two-phases;Experimental studies have been carried ...


A Metallurgical Approach Toward Alloying In Rare-Earth Permanent Magnet Systems , Daniel James Branagan Jan 1995

A Metallurgical Approach Toward Alloying In Rare-Earth Permanent Magnet Systems , Daniel James Branagan

Retrospective Theses and Dissertations

A metallurgical approach was developed toward alloying in rare earth permanent magnet systems to allow for microstructural enhancement and control during solidification and subsequent processing. Compound additions of Group IVA, VA, or VIA transition metals (TM) along with carbon were added to the Nd[subscript]2Fe[subscript]14B system (2-14-1). Transition metal carbides will form in the quintary Nd-Fe-B-TM-C system if the phase stability of the precipitates in the specific multicomponent system is higher than the phase stability of all other phases involving the additive elements and the constituent elements. Transition metal carbide formation was found in the Group IVA ...


Ultrasonic Measurement Of Drawability (R-Values) Of Low Carbon Steel Sheets , Kaveh Forouraghi Jan 1995

Ultrasonic Measurement Of Drawability (R-Values) Of Low Carbon Steel Sheets , Kaveh Forouraghi

Retrospective Theses and Dissertations

The present research was designed to evaluate an ultrasonic technique for measuring the drawability of low carbon steel sheets nondestructively. This technique, which uses electro magnetic acoustic transducers (EMAT's) is embodied in a fully automatic ultrasonic device called Ultra-Form, which was developed by Iowa State University in 1990. EMAT transducers generate the ultrasonic pulses in the sheet (without any need for a coupling medium) whose velocities are then related to the microstructural factors (crystallographic texture) that control drawability in rolled sheets. Drawability (usually interpreted by measuring r-values of low carbon steels) is an important property indicative of the formability ...