| Severe plastic deformation methods (SPD) have received great attentions through its feasibility to produce bulk nano-materials and ultrafine grained materials. Mechanical properties can be strengthened or improved in materials processed by SPD, as well as some outstanding physical or chemical properties. In this dissertation typical metals of (fee) copper, nickel and aluminum, (bec) tungsten and (hep) titanium are chosed for the investigations on their microstructures evolution and mechanical properties development during severe plastic deformation.The most popular mechanisms accounted for grain refinement during SPD could be concluded as disclination, dislocation cell/cell block, shear bands and mechanical twinning. And continuous dynamic recrystallization (cDRX) has gained more and more attentions during SPD processing. It showed that under states of large strain (e.g.95%of pressing reduction), high strain rate and low temperature, discontinuous recrystallization may be restricted because long range of grain boundary immigrations are blocked with uniform deformed microstructure (e.g.70%of HAGB in aluminum), and thus cDRX could occur. All these parameters are hard to achieve during usual plastic deformation and studies of cDRX are thus limited. However, those parameters are fit to the features of SPD processing, which could pushed forward with the development of cDRX investigation, and at meanwhile it could provide a new path of investgating grain refinement mechanism during SPD processing. The present work is going to investigate microstructure evolution and mechanical property development of fee metals copper, nickel and aluminum with diffent Stacking fault energy (SFE) during ECAP processing, room temperature.Hard to deform materials exhibit poor feasibity for deformation at low temperature, however, those materials could be refined by SPD methods, by which an increase of mechanical property can be also achived. Tungsten is the metal of highest melt temperature and the one of highest strength, which has many applications on both industry and military areas; it is obviously that the improvement on ductility has great importance on military applications of tungsten. And by employed SPD processing, ultrafine grained tungsten would show an increase in mechanical property and a possibility of ductility improvement as well.Pure titanium is one of typical hep metals, the strengthening of which are very important for its application on both structure area and medical applications. Mechanical twinning is proved to be effective on mechanical strengthening in fee metals, however, such study in hep metals are still rare, although twining has played an important part on deformation of hep materials.The present investigation has paid attentions on the above three problems on SPD study, and the main results are as follows,(1) Aluminum of high SFE (ym-200 mJ/m2)may have a continuous microstructure evolution through the way of'Formation of lamellar boundaries with low dislocation densities→division of lamellar boundaries into subgrains→Formation of equiaxed (sub)grain'during ECAP processing at R.T., while as in the case of low SFE copper (ym～40 mJ/m2), a continuous microstructure evolution might evolute through the way of 'Dislocations tangled into cecullar wall→dislocation condensed into subgrain boundaries→subgrain combined into grains'during ECAP processing at R.T.. Nickel has a combined characters of microstructure evolution on both of those in aluminum and in copper during ECAP processing at R.T..(2) SFE (ym) and Zener-hollomon parameter (Z) has great effections on the way of dynamic recrystallization, it's inferred that a condition of ym·In2Z> 30 could get a result of continuous reaction of dynamic recrystallization during deformation.(3) CP tungsten has been processed by three different SPD processing. An ultrafine grained (UFG) tungsten of～1μm are obtained by ECAP with an initial grain size of-50μm, which has resulted in a decrease of 70-130℃of DBTT in UFG tungsten. An ultrafine grained tungsten of 150 nm has been produced by high pressure torsion (HPT) processing at 450℃, an 100%increase in mechanical propertied has been achived in such microstucture, which has also show extremely good thermal stability on subsequent annealing.(4) CP titanium has been processed by 1 pass and 2 passes of ECAP at room temperature, at a speed of 0.5 mm s-1 and 0.05 mm s-1, it showed that an increase in strength is related only to the occurrence of mechanical twinning, which has resulted in～730 MPa of tensile yield strength by 2 passes of ECAP at 0.05 mm s-1, which is higher than that processed by 8 passes of ECAP and is close to that of Ti-6A1-4V.(5) TEM results showed a dissociation of{1012} plane diffraction patterns in SAED of as processed titanium. And dislocation equations are studied on base of interaction of a slip dislocation and{1012} TB, which aotumatically resulted in 1/2[0001] Frank dislocations. Furtherly, it is concluded that the pile up of Frank dislocation on{1012} TB could reduce the tilt angle of basal plane in titanium. This dissociation of diffraction patterns are common to be seen in metals where mechanical twinning play a part of deformation.
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