The Dahlonega Nugget (Vol VII, no. 45)

Hew to the line -- keep the chips a flying. Covers week of October 17, 1896. You can also view this on https://archive.org/details/AWC_1897_2FEB/page/n11/mode/2uphttps://digitalcommons.northgeorgia.edu/cain/1044/thumbnail.jp

Optimizing superplastic response in lithium containing aluminum-magnesium alloys.

http://archive.org/details/optimizingsuperp00munrNAN

Surface engineering of corrosion, environmental fracture, cavitation & impingement resistant materials

There is a need for materials that are highly resistant to corrosion, environmental fracture, cavitation, and liquid droplet impingement, especially within the Navy. Several novel approaches to enhancing the cavitation and impingement resistance of ship and aircraft components are discussed. These approaches include: (1) new ultra-hard amorphous-metal coatings, applied with a hydrogen-fueled HVOF process; (2) coatings with extreme interfacial bond strength, produced with LLNL’s new laser-based HVLAD process; (3) nickel aluminide coatings with nano-diamond strengthening and hardening, applied with a combination of cold spray and post- deposition heat treatment with intense diode sources; (4) diode-assisted friction stir processing for the elimination of surface defects in large cast propellars; and (5) laser peening for the elimination of residual tensile stresses, and the associated fatigue and environmental cracking. This paper discusses several novel approaches to the development of such materials, through surface engineering, and the benefits that will be enjoyed if such a developmental effort is successful.Department of Energy (DOE)Contract DE-AC52-07NA2734

The Dahlonega Nugget (Vol. 1, nos. 1, 3); The Dahlonega Signal (Vol. 50, no. 23)

The Dahlonega Signal: A record of mining, agricultural, local, miscellaneous and general news. The Dahlonega Nugget: Published by W. G. McNelley and S. H. Williams Covers weeks of March 14, March 28, 1890. You can also view this on https://archive.org/details/AWC_1890_3MAR/page/n7/mode/2uphttps://digitalcommons.northgeorgia.edu/cain/1024/thumbnail.jp

Peak Stir Zone Temperatures during Friction Stir Processing

The stir zone (SZ) temperature cycle was measured during the friction stir processing (FSP) of NiAl bronze plates. The FSP was conducted using a tool design with a smooth concave shoulder and a 12.7-mm step-spiral pin. Temperature sensing was accomplished using sheathed thermocouples embedded in the tool path within the plates, while simultaneous optical pyrometry measurements of surface temperatures were also obtained. Peak SZ temperatures were 990 ⁰Cto 1015 ⁰C (0.90 to 0.97 TMelt) and were not affected by preheating to 400⁰C, although the dwell time above 900 ⁰C was increased by the preheating. Thermocouple data suggested little variation in peak temperature across the SZ, although thermocouples initially located on the advancing sides and at the centerlines of the tool traverses were displaced to the retreating sides, precluding direct assessment of the temperature variation across the SZ. Microstructure-based estimates of local peak SZ temperatures have been made on these and on other similarly processed materials. Altogether, the peak-temperature determinations from these different measurement techniques are in close agreement

Optimization of the Strength-Fracture Toughness Relation in Particulate-Reinforced Aluminum Composites via Control of the Matrix Microstructure

The article of record as published may be found at http://dx.doi.org/10.1007/s11661-998-0119-9The evolution of the microstructure and mechanical properties of a 17.5 vol. pct SiC particulatereinforced aluminum alloy 6092-matrix composite has been studied as a function of postfabrication processing and heat treatment. It is demonstrated that, by the control of particulate distribution, matrix grain, and substructure and of the matrix precipitate state, the strength-toughness combination in the composite can be optimized over a wide range of properties, without resorting to unstable, underaged (UA) matrix microstructures, which are usually deemed necessary to produce a higher fracture toughness than that displayed in the peak-aged condition. Further, it is demonstrated that, following an appropriate combination of thermomechanical processing and unconventional heat treatment, the composite may possess better stiffness, strength, and fracture toughness than a similar unreinforced alloy. In the high- and low-strength matrix microstructural conditions, the matrix grain and substructure were found to play a substantial role in determining fracture properties. However, in the intermediate- strength regime, properties appeared to be optimizable by the utilization of heat treatments only. These observations are rationalized on the basis of current understanding of the grain size dependence of fracture toughness and the detailed microstructural features resulting from thermomechanical treatments.United States Army Research OfficeArmy Research LabratoryUnited States Air Force Office of Scientific ResearchWright Materials LabratoryDWA Composite

Microstructure and corrosion behavior of the friction stir welded joints made from ultrafine grained aluminum

Joints made from ultrafine grained aluminium alloy 1050 are investigated in order to examine the corrosion behavior and microstructural changes between base materials and stir zones. Samples in the initial state, after four and eight passes of Incremental ECAP (I-ECAP) process were joined with similar plates using Friction Stir Welding. Initially refined microstructure after I-ECAP transformed to homogenous few micron sized grains structure in stir zones. AlFeSi particles present in the microstructure became fragmented during plastic deformation and welding process. The observed minor differences in corrosion resistance include slightly higher values of corrosion potentials but more complex pits' morphology for I-ECAP processed samples comparing to the stir zones