Low-Temperature Anelastic Property of Nanocrystalline Ag Fabricated by Gas Deposition Method

It was reported that the internal friction (Q-1) of nanocrystalline (n-) Au and n-Cu showed a rapid increase linearly with temperature above ~200 K. Since the rapid increase in Q-1 decreased with the progress in the grain growth, it was suggested that the anelasticity of grain boundaries in n-Au and n-Cu was thermally activated above ~200 K. In order to pursue the intrinsic behavior of the grain boundaries in n-metals, the internal friction of n-Ag was measured and the result was compared with those of n-Au and n-Cu. Similar to n-Au and n-Cu, Q-1 of n-Ag was also showed the increase linearly with temperature above ~200 K. However, the onset temperature for the linear increase in Q-1 of n-Ag was slight lower than those of n-Au and n-Cu and it can be attributed to the lower activation energy of the grain boundary self-diffusion in Ag.据报道，纳米晶金 (nanocrystalline Au，简称n-Au) 与纳米晶铜 (nanocrystalline Cu，简称n-Cu) 的内耗 (internal friction，符号Q⁻¹) 在约200 K以上随温度呈快速线性增长趋势。随着晶粒长大进程的推进，该内耗的增幅逐渐降低，由此表明纳米晶金与纳米晶铜的晶界滞弹性在约200 K以上为热激活过程。为探究纳米晶金属中晶界的本征行为，研究者对纳米晶银 (nanocrystalline Ag，简称n-Ag) 的内耗进行了测量，并将其测试结果与纳米晶金、纳米晶铜的结果进行对比。与纳米晶金和纳米晶铜的结果相似，纳米晶银的内耗Q⁻¹在约200 K以上同样呈现线性增长趋势。不过，纳米晶银内耗出现线性增长的起始温度略低于纳米晶金与纳米晶铜，该现象可归因于银的晶界自扩散激活能更低。