Engineering topics
Publications and source records attributed to Lenel, F. V..
Discussion of the effects of capillarity-induced stresses on dislocations during early stage sintering. A special version of Hirth's (1963) theoretical calculation procedures modified to describe dislocation nucleation on planes meeting the sintering body's neck surface obliquely is shown to predict plastic flow at stress levels know to exist between micron size metal particles in the early stages of sintering.
The effect of solute additions on the steady-state creep behavior of coarse-grained dispersion-strengthened aluminum alloys was studied. Recrystallized dispersion-strengthened solid solutions were found to have stress and temperature sensitivities quite unlike those observed in single-phase solid solutions having the same composition and grain size. The addition of magnesium or copper to the matrix of a recrystallized dispersion-strengthened aluminum causes a decrease in the steady-state creep rate which is much smaller than that caused by similar amounts of solute in single-phase solid solutions. All alloys exhibited essentially a 4.0 power stress exponent in agreement with the model of Ansell and Weertman. The activation energy for steady-state creep in dispersion-strengthened Al-Mg alloys, as well as the stress dependence, was in agreement with the physical model of dislocation climb over the dispersed particles.
Steady-state creep rates were measured for two preparations of a dispersion-strengthened alloy of silver with 1 mol % gallium oxide. One preparation, an internally-oxidized type, had a grain size 40 times that of the other preparation, which was a consolidated-powder type of alloy. The temperature and stress dependence of the steady-state creep rate differs widely for the two alloys and must be attributed to the difference in grain size. The activation energy for steady-state creep of the internally-oxidized coarse grained material is near that for self-diffusion of silver, which strongly indicates a creep process controlled by dislocation climb.
Gallium oxide particles effects on Ag-Ga matrix single crystals critical resolved shear stress
Temperature rise of micron sized silver particles on carbon film due to electron beam heating, setting up heat balance equation
Plastic deformation of internally oxidized dispersion strengthened silver magnesium alloys, noting hardening effect dependence on oxidation temperature
High temperature steady state creep rate analysis of pure Ag and internally ionized Ag-Mg alloys
Hardness and lattice parameter increase effect on oxidation temperature of internally oxided Ag-Mg and Ag-Al alloys
Zinc-base alloy creep resistance and structure in extruded wire prepared by powder metallurgy
Oxidation rate effect on microstructure, hardness and lattice parameters of internally oxidized silver-magnesium alloys
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Aluminum oxide particle growth in nickel matrix
Temperature dependence of the yielding behavior of sap-type dispersion strengthened alloys
Creep of a recrystallized aluminum sap-type alloy
Criteria for yielding of dispersion-strengthened alloys
Recrystallization of cold-drawn sintered aluminum powder
A dislocation model is presented in order to account for the yield behavior of alloys with a finely dispersed second-phase. The criteria for yielding used in the model, is that appreciable yielding occurs in these alloys when the shear stress due to piled-up groups of dislocations is sufficient to fracture or plastically deform the dispersed second-phase particles, relieving the back stress on the dislocation sources. Equations derived on the basis of this model, predict that the yield stress of the alloys varies as the reciprocal square root of the mean free path between dispersed particles. Experimental data is presented for several SAP-Type alloys, precipitation-hardened alloys and steels which are in good agreement with the yield strength variation as a function of dispersion spacing predicted by this theoretical treatment.