Metallurgy Commons^™

Influence Of Fraction Of High Angle Boundaries On The Mechanical Behavior Of An Ultrafine Grained Al-Mg Alloy, R. Kapoor, N. Kumar, R. S. Mishra, C. S. Huskamp, K. K. Sankaran

Materials Science and Engineering Faculty Research & Creative Works

The mechanical behavior of ultrafine grained AA5052 processed through different techniques-rolled, annealed, friction stir processed (FSP) and equal channel angular pressed (ECAP)-were compared and correlated with microstructure. the microstructure was characterized using electron back scattered diffraction to obtain the boundary spacing, the fraction of high angle boundaries and to estimate the dislocation density from local misorientations. Both FSP and ECAP conditions had ultrafine boundary spacing, but the fraction of high angle boundaries was larger for the FSP condition. Tensile deformation carried out at 297K, and 10-3s-1 showed a lower work-hardening rate and recovery rate for FSP as compared to the …

Friction Stir Processing Of Commercial Grade Marine Alloys To Enable Superplastic Forming, Christopher B. Smith, Arun Mohan, Rajiv S. Mishra, Murray Mahoney, Mike Miles, Scott M. Gillis, Lee M. Cerveny, Gerald Opichka

Materials Science and Engineering Faculty Research & Creative Works

The use of friction stir processing (FSP) on marine grade aluminum sheet has been investigated with the objective of locally enhancing the material properties. This can potentially allow low-cost commercial grade aluminum to be used in superplastic forming applications or further enhance the formability to allow more complex geometries to be formed. FSP has been demonstrated to enable super plasticity (uniform elongations >250%) in 5083-H116 over a range of friction stir processing conditions. © (2010) Trans Tech Publications.

An Analysis Of Strength And Ductility Of Ultrafine Grained Al Alloys, R. Kapoor, P. S. De, R. S. Mishra

Materials Science and Engineering Faculty Research & Creative Works

This paper brings together and compares data of various ultrafine grained (UFG) Al alloys processed through different routes. in general, the trend of decreasing ductility with increasing strength was observed for the UFG alloys. as compared to the coarse grained (CG) alloys, the UFG alloys show a lower ductility, a lower extent of work-hardening and a lower uniform elongation. Unlike the CG alloys, which show a large fraction of uniform to total elongation, in UFG alloys this fraction varies with processing technique. It is shown here that aging of some UFG Al alloys improves ductility. Further, it is shown that …

Factors Controlling Ductility In Ultrafine Grain Aluminum Alloys Under Monotonic And Cyclic Loading, Partha Sarathi De

Doctoral Dissertations

"Ultrafine grained (UFG) Al processed by severe plastic deformation (SPD) methods are characterized by high strength and a limited uniform ductility. Friction stir processing (FSP), an offshoot of friction stir welding has emerged as a new technique to produce UFG alloys. FSP-UFG Al alloys show a distinctly different behavior with higher uniform elongation and improved high cycle fatigue life as compared to other SPD processed variants. The objective of this work was to study the microstructural basis for such mechanical behavior in FSP-UFG Al alloys.

To study the mechanical behavior of FSP Al alloys, a subsize bending fatigue and uniaxial …

Characterization Of Diamond Thin Films And Related Materials, Travis K. Mckindra

Doctoral Dissertations

"Thin carbon films including sputtered deposited graphite and CO₂ laser-assisted combustion-flame deposited graphite and diamond thin films were characterized using optical and electron microscopy, X-ray diffraction and micro-Raman spectroscopy. Amorphous carbon thin films were deposited by DC magnetron sputtering using Ar/O₂ gases. The film morphology changed with the oxygen content. The deposition rate decreased as the amount of oxygen increased due to oxygen reacting with the growing film. The use of oxygen in the working gas enhanced the crystalline nature of the films. Graphite was deposited on WC substrates by a CO₂ laser-assisted O₂/C₂H₂ combustion-flame method. Two distinct microstructural areas …

Dependency Of Machinability In Gray Cast Iron On Nitride-Induced Age Strengthening, Jared Teague

Doctoral Dissertations

"Work of previous researchers has suggested that room temperature age strengthening in gray cast irons improves machinability. Verification and quantification of the machinability improvement is important to industry. Improved machinability will reduce overall manufacturing costs and reduce raw material consumption by decreasing the rate at which tools are replaced. Experimental work was performed to determine a connection between improved machinability in gray cast iron and changes in machining mechanics. An industrial tool wear study verified that age strengthening improved machinability by reducing tool wear to less than one-quarter of the unaged value. Laboratory tests on iron castings from the same …

Understanding Corrosion Of Ni₃(Si,Nb) Alloys In Hot Sulfuric Acid, Jen-Hsien Hsu

Doctoral Dissertations

"The Sulfur-Iodine thermochemical cycle has been proposed as a method for producing large quantities of hydrogen gas from water. However, the extreme operating environments involved limit the possible materials for construction.

Through proper heat treatment and composition control, the modified patented Ni₃(Si,Nb) alloy keeps high temperature strength to greater than 750⁰C and can be deformed by cold rolling more than 50% using multiple passes and intermediate anneals. The corrosion resistance is reproducible and maintains less than 5 mpy for a broad range of boiling sulfuric acid concentrations, including 70 wt%.

In the boiling 70 wt% sulfuric acid corrosion tests, kinetic …

Fluid Flow Related Phenomena And Inclusion Motion In Continuous Casting Strands, Yufeng Wang

Doctoral Dissertations

"To improve the efficiency of the continuous casting process and the quality of its products, this dissertation mainly investigated fluid flow related phenomena and inclusion motion in continuous casting. Mathematical simulation was performed for this purpose. Both a slab caster and a billet caster were investigated. In the study of the slab caster, the application of electromagnetic brake field on the slab mold was evaluated. The results indicated that the magnetic force decelerated the high speed steel jet, stabilized the top fluctuation, and prevented the bias flow inside the mold. The other study of this slab caster involved the fluid …