Non-equilibrium solute partitioning in a laser re-melted Al–Li–Cu alloy

Aluminum–lithium alloy AA2199 was rapidly solidified through the application of a laser re-melting process to determine the relationship between laser pulse energy and microsegregation during solidification. It was determined that laser pulse energies of the order of 0.125–0.5 J s resulted in a fine cellular solidification structure. Through comparison of the measured cell spacing with that predicted by the Kurz–Giovanola–Trivedi (KGT) model it was possible to estimate that solidification front velocities (SFV) of between 3 and 25 cm s^?1 occurred during solidification. The SFV calculated from the KGT model was then input into the continuous growth model for solute trapping developed by Aziz to predict the deviation from equilibrium partitioning during solidification for all pulse energy levels employed. The chemical profile of lithium within the re-melted samples was measured using X-ray photoelectron spectroscopy and compared with that expected for equilibrium segregation. Measurement of the lattice parameter via X-ray diffraction revealed that the solute trapping phenomenon resulted in the formation of a super-saturated solid solution, as is evident through a reduction of the lattice parameter from 4.0485 Å for the starting material to 4.0399 Å in the material re-melted with a pulse energy of 0.125 J.     

Heat and mass transfer to spheres in high-temperature surroundings

An experimental investigation of the combined natural and forced convective effects was carried out which involved the measurement of the rate of evaporation of water from porous stationary spheres (1/4, 3/8 and 1/2-in. in diameter) under steady conditions in an electrically-heated stainless steel chamber. The spheres were suspended in a stream of super-heated steam at atmospheres ranging from 50 to 1000°K. Both the opposing and aiding flow cases were investigated. The Reynolds number varied from 0 to 1489 and the turbulence intensity was less than 1%. The parameter [(Gr)/(Re²)] was found to be of fundamental importance in correlating the results. The rates of heat transfer in the mixed flow region for the opposing flow case was higher than for aiding flow. The transition between the two mechanisms was found to be gradual but very complex in the case of opposing flow.     

Failure of a Fusion Welded Ball Joint as a Result of Modification in MnS Direction

A failure investigation was performed on a ball joint from an ATV front suspension system. The location of the fracture was the bearing ball/stud interface, which is a fusion-welded joint, and occurred after approximately 20 h of field-testing. The two parts are made out of carbon steel and were previously heat-treated. Many elongated MnS inclusions were found in the stud material, and these inclusions were parallel to the symmetry axis. Even though these inclusions were not significantly sized, their number was important. Macroscopic evidence showed that the joint failed in a ductile mode under centered tensile overload. Microscopic examination showed that MnS orientation changed in the fusion joint area. The inclusions had been redirected during the welding process and laid parallel to the fracture surface. This reorientation caused a significant decrease in the effective cross section of the joint and overload fracture occurred.     

A naturalistic study of the impact of acute physical activity on feeling states and affect in women.

This field study used experience sampling procedures to examine the relationship of feeling states and affect to acute bouts of physical activity in women. Participants (N?=?86) completed brief affect and feeling state measures (a) in response to random stratified pager tones and (b) before and after acute bouts of vigorous physical activity for 6 weeks. Analysis of averaged difference scores revealed that acute vigorous physical activity was associated with significant improvements in affect and feeling states, particularly in feelings of revitalization. Moreover, within-subject analyses indicated that the effects were moderated by preactivity scores, with the greatest improvements seen when women felt worst before activity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Materials characterization using high-resolution scanning-electron microscopy and x-ray microanalysis

Low-voltage field-emission scanning-electron microscopy offers the possibility to characterize a wide range of materials. Electron optics in an electron beam column have improved in recent decades and now probe diameters of 1–10 nm can be obtained, allowing a wide range of applications to be explored. This article discusses the applications of low-voltage microscopy, including the characterization of nanoparticles, super-lattice structures, and carbon nanotubes.     

Experimental milling moment model in orthogonal cutting condition: to an accurate energy balance

The control of cutting energy parameters is essential to optimize the cutting condition during the milling process. Our previous works (Cahuc et al., Int J Adv Manuf Technol 18(9):648?C656, 2001; Darnis et?al. 2000) have shown the existence of the six components of the cutting mechanical actions. Thus, the influence of geometric and kinematic parameters on the six components must be quantified. Based on the experimental approach explained in our last works (Albert et al., 2008a, b), this study proposes an energetic criterion characterizing the cutting moment in orthogonal cutting condition. Then, the energy balance has to take into account the cutting moment, highlighting the utility of this criterion. Therefore, the cutting moment model proposed allows an accurate evaluation of the energy balance and the mechanical actions (forces and moments) applied to the workpiece. Consequently, the cutting parameters can be chosen in order to optimize the cutting power consumption.     

Quantitative x-ray microanalysis of spherical inclusions embedded in a matrix using a SEM and Monte Carlo simulations

The current schemes of quantification of x-ray microanalysis in the SEM [ZAF and σ(ρZ) methods] are valid for specimens of homogeneous composition. The determination of the chemical composition of small inclusions using these techniques is impossible because the volume of x-ray emission is not of homogeneous composition. A scheme of quantification to determine the composition of small inclusions embedded in a matrix has been developed using Monte Carlo simulations. This scheme is similar to that developed by Kyser and Murata (1974) for the quantification of thin foils deposited on a substrate using x-ray microanalysis in the SEM.