Microscale effects on creep properties of microcastings at room temperature

The overall size of the microcasting prepared is in the range of micron, whose creep behavior cannot be measured through conventional tensile creep test. Its creep characteristics at room temperature are measured by Berkovich nanoindentation tests of high precision. Then based on the concept of "work of indentation", the strain rate sensitivity of creep (m) is obtained from the load-depth curves. The results show that the m obtained in the top and root are -0.13451 and -0.12346 respectively. Whereas m in conventional castings is 0.40365, and the obvious micro-scale effect are found. It is analyzed that massive Al atoms induced by rapid solidification of micro-castings are solid solution existing in Zn base in the form of supersaturation. In this experiment, Al atoms used as solute atoms are diffused by pipe diffusion, then pin dislocations. This results in dynamic strain aging (DSA).