Leslie G. Bland

Assessing the Corrosion of Commercially Pure Magnesium and Commercial AZ31B by Electrochemical Impedance, Mass-Loss, Hydrogen Collection, and Inductively Coupled Plasma Optical Emission Spectrometry Solution Analysis

The corrosion of commercially pure magnesium (Mg) and AZ31B-H24 with simultaneous measurements of electrochemical impedance (EIS) and hydrogen gas evolved over a 24 h immersion period was studied i...

A Compilation of Corrosion Potentials for Magnesium Alloys

A compilation of the reported corrosion potentials for Mg alloys and selected intermetallic compounds is presented. This study presents a galvanic series for Mg alloys based on a collection of data...

Metallurgical and Electrochemical Characterization of the Corrosion of AZ31B-H24 Tungsten Inert Gas Weld: Isolated Weld Zones

The corrosion behavior of a magnesium (Mg) alloy, AZ31B-H24, joined by tungsten inert gas welding was investigated. The corrosion rates and morphology were characterized for each weld zone in isola...

Ultrasonic Backscattering Measurements of Grain Size in Metal Alloys

Grain size is a key property that is carefully controlled during processing to create specific mechanical properties and reliability in final components. Achieving specific grain sizes is especially important in aircraft engines where temperatures can range from 260°C at the bore to 704°C at the rim, creating fatigue cracking in the bore and creep damage in the rim region. These competing failure mechanisms led to nickel alloy disks possessing fine-grains, ~5 microns in the bore and coarse-grains, ~80 micron in the rim. We created an automated ultrasonic measurement tool which calculates grain size from ultrasonic backscattering measurement. The tool unifies the entire process including controlling the ultrasonic scanner, data acquisition, experimental and theoretical backscattering calculations, numerical optimization to obtain grain size, and visualization. We tested our tool on IN718, Waspaloy, Rene 88 and Alloy 10. Our automated “Ultrasonic Metallography Tool” produced a map of the grain size where the color scale is the grain size. The authors believe this is the first time such a map has been generated automatically from ultrasonic backscattering measurements. Our results compare favorably with traditional metallography agreeing to within 2 microns for some alloys.

Acoustic scattering to measure dispersed oil droplet size and sediment particle size

The use of sound waves in oceanographic environments is well established including active sonar applications for mapping seafloors, for submarine detection, and for passive listening. Acoustic waves have been used for many years to study the ocean, including detecting and identifying objects in the water column, and the measuring the seafloor and sub seafloor properties. One of the key parameters of the acoustic field is the amplitude of the wave which scatters from the seafloor or from objects in the water column. The amplitude, time of flight, and frequency response can be used to map the seafloor, measure current flow, or to detect and classify objects in the water column. In addition to these standard uses, acoustics can also be used to size particulates including sediment, oil droplets and gas bubbles in the water. Our particular application for this work is to detect, classify, and size sediment particles and separately, oil droplets suspended in the water column using knowledge of the acoustic backscattering and attenuation. Specifically, we have measured and separated the absorption, single scattering and multiple scattering contributions to attenuation measurements. Our results show that the absorption dominates the attenuation at low ka values <;<; 1 and multiple scattering and particle-particle interactions dominate at higher ka values when ka >;~1 with a transition between theses ranges depending on the concentration of the suspensions. The physics has been proven out on silica particles in water and work is ongoing on suspended sediment and suspensions of oil droplets.

Mitigation of Corrosion on AZ31B-H24 Tungsten Inert Gas Welds in Chloride Environments via Laser Surface Modification

Laser surface modification (LSM) was performed on autogenously welded samples to homogenize the weld microstructure and mitigate poor corrosion performance. Characterization of weld zone corrosion ...