This study focuses on the fracture characteristics of Cu6Sn5 and Cu3Sn micro beams under micro-cantilever bending tests. These micro beams were fabricated by focused ion beam (FIB) from the Sn-rich ...solder joints aged at 175 °C for 1132.5 h, and then tested using a nanoindenter with a flat tip. Experimental results show that both Cu6Sn5 and Cu3Sn micro beams underwent elastic deformation before their failure. From fractographic analysis, both cleavage fracture and intergranular fracture can be identified from the tested Cu6Sn5 micro beams, while only intergranular fracture was found in Cu3Sn micro beams. Furthermore, based on the experimental results, finite element analysis was carried out to evaluate the tensile fracture strength and strain of Cu6Sn5 and Cu3Sn micro beams. For Cu6Sn, the tensile fracture strength was estimated to be 1.13 ± 0.04 Pa and the average tensile strain was 0.01. The tensile fracture strength and strain of Cu3Sn were evaluated to be 2.15 ± 0.19 GPa and 0.016, respectively.
Display omitted
•Cu6Sn5 and Cu3Sn micro-beams were prepared by FIB for cantilever bending test using a nanoindentation system.•The correlation between IMCs crystalline structures and the fracture characteristics of Cu6Sn5 and Cu3Sn was proposed.•Finite element analysis was conducted to clarify the fracture modes of Cu6Sn5 and Cu3Sn under micro-cantilever bending.•The fracture strength of Cu6Sn5 and Cu3Sn were estimated based on simulation and micro-mechanical test.
Non-conventional methods of machining are used for many engineering applications where the traditional processes fail to be cost-effective. Such processes include Ion Beam Machining (IBM), focused ...ion beam (FIB) machining and plasma discharge machining. The mechanisms of material removal and associated hardware and software developed for industrial applications of these fascinating electro-physical and chemical machining processes are reviewed together with the latest research findings.
Nanocutting mechanism of single crystal 6H-SiC is investigated through a novel scanning electron microscope setup in this paper. Various undeformed chip thicknesses on (0001) < 1–100 > orientation ...are adopted in the nanocutting experiments. Phase transformation and dislocation activities involved in the 6H-SiC nanocutting process are also characterized and analyzed. Two methods of stress-assisted and ion implant-assisted nanocutting are studied to improve 6H-SiC ductile machining ability. Results show that stress-assisted method can effectively decrease the hydrostatic stress and help to activate dislocation motion and ductile machining; ion implant-induced damages are helpful to improve the ductile machining ability from MD simulation and continuous nanocutting experiments under the online observation platform.
The Au–Al intermetallic compounds (IMCs) were commonly regarded as brittle within wire bonding interfaces. Here the in-situ micro-pillar compression tests of Au4Al IMCs were carried out to verify ...their intrinsic mechanical property. The result clearly shows that, surprisingly, the Au4Al IMC is ductile, while the yield stress appeared to be about 1 GPa. Furthermore, upon the compression tests of Au4Al IMC micro-pillars with initial crack, no brittle fracture was observed; instead, the plastic deformation of Au4Al was shown via shear band. This work suggests that pristine Au4Al IMC is ductile and crack-resistant, which provides new insights for wire bonding process and technology.
Display omitted
•The in-situ compression test confirms that the Au4Al intermetallic compound is both ductile and strong.•The Au4Al intermetallic compound has the capability to prevent crack propagation during the compression test.•Au-rich Au–Al intermetallic compounds are proved to be ductile and crack-resistance.
When the water droplets are on some superhydrophobic surfaces, the surface only needs to be inclined at a very small angle to make the water droplets roll off. Hence, building a superhydrophobic ...surface on the material substrate, especially the metal substrate, can effectively alleviate the problems of its inability to resist corrosion and easy icing during use, and it can also give it special functions such as self-cleaning, lubrication, and drag reduction. Therefore, this study reviews and summarizes the development trends in the fabrication of superhydrophobic surface materials by non-traditional processing techniques. First, the principle of the superhydrophobic surfaces fabricated by laser beam machining (LBM) is introduced, and the machining performances of the LBM process, such as femtosecond laser, picosecond laser, and nanosecond laser, for fabricating the surfaces are compared and summarized. Second, the principle and the machining performances of the electrical discharge machining (EDM), for fabricating the superhydrophobic surfaces, are reviewed and compared, respectively. Third, the machining performances to fabricate the superhydrophobic surfaces by the electrochemical machining (ECM), including electrochemical oxidation process and electrochemical reduction process, are reviewed and grouped by materials fabricated. Lastly, other non-traditional machining processes for fabricating superhydrophobic surfaces, such as ultrasonic machining (USM), water jet machining (WJM), and plasma spraying machining (PSM), are compared and summarized. Moreover, the advantage and disadvantage of the above mentioned non-traditional machining processes are discussed. Thereafter, the prospect of non-traditional machining for fabricating the desired superhydrophobic surfaces is proposed.
The influence of Pt layer thickness on the fracture behavior of PtNiAl bond coats was studied in situ using clamped micro-beam bend tests inside a scanning electron microscope (SEM). Clamped beam ...bending is a fairly well established micro-scale fracture test geometry that has been previously used in determination of fracture toughness of Si and PtNiAl bond coats. The increasing amount of Pt in the bond coat matrix was accompanied by several other microstructural changes such as an increase in the volume fraction of α-Cr precipitate particles in the coating as well as a marginal decrease in the grain size of the matrix. In addition, Pt alters the defect chemistry of the B2-NiAl structure, directly affecting its elastic properties. A strong correlation was found between the fracture toughness and the initial Pt layer thickness associated with the bond coat. As the Pt layer thickness was increased from 0 to 5 µm, resulting in increasing Pt concentration from 0 to 14.2 at.% in the B2-NiAl matrix and changing α-Cr precipitate fraction, the initiation fracture toughness (K
IC) was seen to rise from 6.4 to 8.5 MPa·m1/2. R-curve behavior was observed in these coatings, with K
IC doubling for a crack propagation length of 2.5 µm. The reasons for the toughening are analyzed to be a combination of material's microstructure (crack kinking and bridging due to the precipitates) as well as size effects, as the crack approaches closer to the free surface in a micro-scale sample.
The effectiveness of the novel micro textured tools developed as an attempt to improve the machinability of Ti6Al4V material is studied. Different types of textures were developed on the rake face of ...the tools and subsequently coated with a solid lubricant (tungsten disulfide). Square and circular textures are developed for the first time. The textured and coated tools were used for machining Ti6Al4V. Adhesion of the material to the rake face of the tools is observed to be decreased considerably although not eliminated completely. Maximum reduction in the main cutting force was 60% for the square textured tools. Friction at the rake face of the tool is reduced considerably which results in the improvement of tool life. The change in adhesion behaviour and the observed reduction in cutting forces are attributed to the reduction in chip-tool contact area owing to the surface texture on the tool inserts. Further, these textures are acting as reservoirs of solid lubricant. Chip morphology is also found to be favourably altered through the reduction in the segmentation frequency (about 40% for square textured tools and 27% for linear textured tools).
PDF
