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Abstract The fracture resistance of nanoscale MEMS films under high frequency impact seriously influences its service life. Nano impact test is a reliable technique to evaluate the fatigue fracture resistance of films by simulating the dynamic cyclic loading conditions. In this paper, a kind of Cu film was prepared by magnetron sputtering. The effects of loading parameters and indenter size on the fatigue damage behavior were studied for the Cu films during by nano impact test technique. The dislocation propagation and crack initiation during the nano impact process were also analyzed by molecular dynamics simulation. The results show that: Nano impact failure of Cu film can be divided into three stages and the main failure forms are cracks and delamination. The increase of the indenter radius leads to the increase of fatigue indentation size. The deformation range and damage accumulation degree of thin film material also increased correspondingly. With the increase of nano impact loading rate, the film material suffered more momentum from the indenter. The fatigue damage energy accumulation accelerates the damage. Highlights • Fatigue property of Cu Film was tested by nano-impact technology. • The nanometer impact fatigue process is simulated by molecular dynamics. • The damage mechanism of nanometer impact fatigue is analyzed. • Relationships between indenter size and loading rate and fatigue property are explained. [ABSTRACT FROM AUTHOR]

Abstract In order to obtain metallurgical shape memory alloy with a better quality, electro-magnetic stirring (EMS) technology is selected as an aiding method during plasma arc deposition (PAD) process. In this work, Ti 51 Ni 49 alloys were successfully produced by EMS-assisted PAD technology. Influence of EMS on the microstructure, phase transformation behavior, micro-hardness and wear resistance of PAD TiNi alloy have been systematically investigated. The PAD TiNi alloy is composed of TiNi coarse columnar dendrites with a certain number of Ti 2 Ni phases distributed in the inter-dendritic regions. Under the action of EMS, TiNi coarse columnar dendrites transform into fine non-dendrites or spheroid grains and the homogeneity of microstructures improves significantly. The implementation of EMS during PAD do not change the path of phase transformation, but improve the degree of phase transformations and reduce the transformation temperatures of PAD TiNi alloy. The EMS-PAD TiNi alloy possesses better dry wear resistance than the PAD TiNi alloy, which can be attributed to the higher degree of pseudo-elasticity of TiNi phases and strengthening of Ti 2 Ni phases. Highlights • Ti 51 Ni 49 shape memory alloys were successfully produced by electromagnetic stirring (EMS) - assisted plasma arc deposition (PAD) technology. • Under the action of EMS, TiNi coarse columnar dendrites transform into fine non-dendrites and its homogeneity improves significantly. • The EMS-PAD TiNi alloy possesses better dry wear resistance than the PAD TiNi alloy due to the higher degree of pseudo-elasticity and strengthening of Ti 2 Ni phases. [ABSTRACT FROM AUTHOR]