Stresses are developed internally in metals when a change in density and strength arises from a phase transformation. It is shown that plastic flow, generally confined to the weaker phase, results from the accommodation of strain due to the transformation front. The form of the plastic flow is considered in terms of the extreme cases of yield and creep behaviour. It is deduced that, for a complete cycle both ways through the transformation temperature, the resultant deformation varies linearly with the applied stress (provided this is small), the fractional volume change on transformation and inversely as the flow stress of the weaker phase. The deformation is not zero in the absence of external stress except where the phase transformation front has random orientation and movement. The theoretically deduced relations are examined experimentally by observing the deformation of specimens with attached weights, giving small tensile stresses, while their temperature was cycled through a transformation point. Phase transformations were examined in a number of metals involving a variety of crystal structures: reasonable agreement between theory and experiment was obtained in all cases.

No abstract

No abstract

Washing decreases the dust concentrations emitted from cotton processed in a model card room. The higher the washing and rinsing temperatures, the greater the reduction. In 5 of 10 trials, the amount of dust added to the background concentration in the card room while processing washed cotton was 0.05 mg/m3 or less. The rate at which cotton can be carded is reduced by washing. Processability is improved by insuring that the cotton is not wet while carding, using a static eliminator at the doffer crush rolls, increasing the relative humidity of the ambient atmosphere, and using a wire-wound feed roll rather than a fluted feed roll at the lickerin. Processability is also improved by applying a finish to the washed cotton.

The phenomenon of superplasticity, where metals deform extensively under small forces and without risk of fracture, is no longer a scientific curiosity. Current studies range from aspects involving metal physics and extend through to areas of industrial application such as metal-working. and fabrication. In the present review superplasticity is defined and its origins surveyed. The salient features in the majority of the reported cases of superplastic behaviour in metals and alloys (and also certain ceramics) are included, together with a brief outline of some technological applications.