Sun Jun's team and collaborators from Xi'an Jiaotong University prepared a nanostructured aluminum / amorphous aluminum nitride multilayer film by magnetron sputtering method. Obvious nano twins and 9R phase were observed in the aluminum layer. Related papers were published in the Journal of Materials recently.
Nano twins as a special microstructure can bring excellent properties such as high strength, high conductivity, and high stability to metal materials. But so far, most researches have been limited to metal materials with medium and low fault energy, such as copper and silver, and it is difficult to form nano twins in metals with high fault energy, such as aluminum.
According to the researchers, the 9R phase is an extended non-coherent twin boundary with a periodic stacking fault structure. Since 9R is more unstable than nano twins in aluminum, its preparation is also more difficult than nano twins. The team proposed the formation mechanism of nano twins and 9R phase of aluminum layer based on heterogeneous interface physics and interface chemistry, that is, the unbonded nitrogen atoms in the amorphous layer of aluminum nitride diffuse into the aluminum layer, forming nitrogen atoms from the interface to the center of the layer The gradient distribution reduces the local stacking fault energy at the interface and induces the nano twins and 9R phase from the interface due to the gradient effect. Since the nitrogen atom distribution gradient is closely related to the thickness of the aluminum layer, a layer thickness scale effect of nano twins and 9R phase is formed. (Reporter Bi Xiaonan reporter Zhang Xingyong)
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