Micro-structure Characterization And Size Effect Of Micro-scale Thin Metal Wires

The mechanical properties of metals at the micro—scale has been a hot topic both inmechanics and in material research. Many researchers have done great job in experimentand micro-structure characterization, which helped a lot in understanding the mechanicalproperties of micro-scale materials and the underlying physical background fundamentally.The mechanical behaviors of pure golden wires with diameters of20μm and50μmhave been obtained in order to unveil the role of Hall-Petch effect and strain gradienteffect. As-received wires were annealed to eliminate residual stress and to gain differentgrains before experiments. Conclusions have been made based on the torsion of annealedwires and characterization of the samples.1. The validity of Hall-Petch effect has been confirmed based on the torsion andtension results of the annealed wires. What’s more, sample size did not influence Hall-Petch effect.2. Quasi-single crystalline wires were prepared based on the evolution trend of grainsize of the samples annealed at different temperatures. Strain gradient was confirmed bycomparing torsion results of quasi-single crystalline wires with different diameters.3. The amplitudes of strain gradient effect and Hall-Petch effect were analyzed. Itwas argued that strain gradient effect was constant while Hall-Petch effect varied withdifferent grain sizes. As a result, when grain sizes were small, Hall-Petch effectsuppressed strain gradient effect. What’s more, these two effects were tangling when grainsizes reached medium. In short, strain gradient effect and Hall-Petch effect werecompeting against each other.