Nanoscale Hierarchical Structure of Twins in Nanograins Embedded with Twins and the Strengthening Effect

Abstract

Hierarchical structures of 20 nm grains embedded with twins are realized in electrodeposited Au–Cu alloys. The electrodeposition method allows refinement of the average grain size to 20 nm order, and the alloying stabilizes the nanoscale grain structure. Au–Cu alloys are face-centered cubic (FCC) metals with low stacking fault energy that favors formation of growth twins. Due to the hierarchical structure, the Hall–Petch relationship is still observed when the crystalline size (average twin space) is refined to sub 10 nm region. The yield strength reaches 1.50 GPa in an electrodeposited Au–Cu alloy composed of 16.6 ± 1.1 nm grains and the average twin spacing at 4.7 nm.

Alloy Electroplating and Young’s Modulus Characterization of AuCu Alloy Microcantilevers

“…The twins were expected to strengthen the AuCu alloy in this study. 20 On the other hand, an increase in the copper content was observed as the CD increased, hence the increased hardness could also be a result of the solid solution strengthening.…”

Effective Young’s Modulus of Complex Three Dimensional Multilayered Ti/Au Micro-Cantilevers Fabricated by Electrodeposition and the Temperature Dependency

“…The sensing ability of a gold-based MEMS accelerometer is reported to reach µG level and the Brownian noise is merely 22 nG/ √ Hz [3]. On the other hand, gold is known to be a relatively soft metallic material among materials commonly utilized in electronics, and electrodeposition is a powerful method to strengthening the gold by grain refinement [7,8] alloying [9][10][11] and introduction of nanotwins [12]. Alternately and repeatedly deposition of gold following by a material with higher mechanical strength to realize a multilayered structure is also an effective strategy [13][14][15].…”