Grain refinement and mechanical properties in ultrafine grained Pd and Pd–Ag alloys produced by HPT

The microstructure and the mechanical properties of ultrafine grained Pd and Pd–x% Ag (x = 10, 20, 40) alloys processed by high pressure torsion (HPT) were thoroughly investigated using transmission and high resolution electron microscopy, XRD analysis and tensile tests. The increased Ag content resulted in decrease of the stacking fault energy (γSF), which made it possible to produce by means of HPT different ultrafine-grained structures in the alloys and to study their superior strength and ductility. The nature of such unique mechanical behaviour is discussed on the basis of analysis of strain hardening mechanisms and effect of stacking fault energy.