Effect of cold compression on precipitation and conductivityof an Al–Li–Cu alloy
Transmission electron microscopy has been used to investigate the effect of increasing the degree of deformation applied by cold compression on the ageing kinetics and electrical conductivity response of an Al–Li–Cu alloy containing Mg and Ag. When cold compressed greater than 3%, the increased dislocation density accelerates the widespread precipitation of the T1 phase resulting in an enhanced age hardening response. The lengthening rate of T1 precipitates is also reduced in this cold compressed condition owing to the reduced local solute supersaturation, a result of the widespread precipitation of T1 plates. Cold compression by less than 3% does not increase the age hardening response, and the precipitation of GP zones/θ″ appears to be suppressed. Precipitation of the T1 phase is also not significantly enhanced compared with that of the more than 3% cold compressed conditions. The anomalous decrease in electrical conductivity is associated with the nucleation and growth of the T1 phase. Strain fields around T1 precipitates combined with the increased volume fraction of  T1 are thought to be the cause of the anomalous conductivity behaviour.
Nondestructive detection of the T1 phase in AlLi alloys
Aluminium-lithium alloys have attracted the interest of aerospace industries for some time now since the use of such alloys reduces the weight of an airframe by roughly ten percent. The production of these alloys, however, requires precise thermal and/or thermomechanical treatments to insure required material properties. Recently, a strong research interest has developed in the use of sensors for monitoring the state of the material during processing and in-service. On Al 2219, combined eddy current (as a measure of electrical conductivity) and hardness measurements were found to be particularly sensitive to the changes occurring during the aging of such alloys. The electrical conductivity, in general, increases with aging. The explanation for this is that the alloying additions in solid solution are very effective in scattering the conduction electrons. As precipitation occurs the resistivity per solute atom decreases, which in turn increases the conductivity. On the other hand, the hardness increases due to precipitation hardening, at least up to peak hardness conditions. Loss of coherency with the matrix and growth of particles reverse the latter trend. In the authors' efforts to characterize the thermal history and the mechanical properties of Al-Li alloy 2090 by NDE techniques, they have noted a strongmore » deviation from the general rule that the conductivity increases with aging. This deviation occurs on samples aged at 200/sup 0/C for extended periods. Noteworthy is the fact that Al 2219 does not show such a conductivity anomaly with aging. In an attempt to understand this phenomenon, Transmission Electron Microscopy (TEM) was used to determine the morphology and crystal structures of the phases present in appropriate samples.« less
Annual review article: Is it time to rethink the gender agenda in entrepreneurship research?
This article develops a critique of contemporary approaches to analysing the impact of gender upon entrepreneurial propensity and activity. Since the 1990s, increasing attention has been afforded to the influence of gender on women’s entrepreneurial behaviour; such analyses have highlighted an embedded masculinity within the entrepreneurial discourse which privileges men as normative entrepreneurial actors. While invaluable in revealing a prevailing masculine bias within entrepreneurship, this critique is bounded by positioning women as a proxy for the gendered subject. This is a potentially limiting analysis that does not fully recognise gender as a human property with myriad articulations enacted throughout entrepreneurial activity. To progress debate, we engage more deeply with the notion of gender as a multiplicity, exploring the implications of such for future studies of entrepreneurial activity.