Papers by Author: Qing Hua Wang

Abstract: The thermo-creep deformation of interconnects related to the residual stress, directly affects their performance and lifetime. In this paper, we proposed an optical method to measure the residual thermo-creep deformation of copper interconnects. This method takes advantages of grating fabrication and the phase-shifting scanning electron microscope (SEM) moiré method. The residual thermo-creep deformation can be acquired through deformation transformation. A one-way grating with frequency of 5000 lines/mm is fabricated on the surface of the copper line in a focused ion-beam (FIB) system. The principal direction of the grating is along the axis of the copper line. The sample is heated in a high temperature furnace under 90 °C for 70 min. The SEM moiré patterns before and after heating are recorded by a field emission SEM in low vacuum. Through the random phase-shifting algorithm, the residual thermo-creep deformation of the copper interconnect line is found to be 500 με. The cause of the tensile strain is analyzed. This work offers an effective technique for measuring the creep deformation of the film lines.

Abstract: TiNi/Al-12%Si alloy is a kind of prospective material used as special energy absorbers for eliminating undesirable noise and mechanical vibration. The investigation on the mechanical properties of this composite alloy is of great importance. In this study, the surface deformation of TiNi/Al-12%Si composite alloy under external loading was measured experimentally by means of DSCM method. Some deformation characteristics of TiNi/AlSi composite alloy under the effect of the tensile load and the interaction between TiNi and AlSi are discussed. In addition, the elastic modulus and the poisson ' s ratio of this alloy were measured as well. The results agrees well with the theory predicts.

Abstract: Martensitic phase transformation can greatly affect the mechanical behaviors and the stress-strain response of shape memory alloys (SMAs). In this study, the effect of martensitic phase transformation on the deformation of a single-crystal TiNi SMA specimen with a triangle crack was investigated experimentally by means of moiré interferometry method. A typical displacement field and the corresponding strain field in areas both around and far from the tip of the crack were measured in a certain time during the loading process in which the tensile load is coupled with the stress-induced martensitic phase transformation. Some characteristics of the deformation and the martensitic phase transformation of the specimen are revealed. These results may provide a reliable support for revealing the fracture mechanism of single crystal TiNi SMAs, and may enable further development in putting forward the failure criterion of SMAs.