The microstructural changes and phase transformation of an ultra-precision machined Zn-Al based alloy were examined using X-ray diffraction and back-scattered electron microscopy techniques. Decomposition of the Zn-rich η phase and the related changes in crystal orientation was detected at the surface of the ultra-precision machined alloy specimen. The effects of the machining parameters, such as cutting speed and depth of cut, on the phase decomposition were discussed in comparison with the tensile and rolling induced microstrucutural changes and phase decomposition. 相似文献
Microthermal machining using scanning thermal microscopy (SThM) has been performed on polymethylmethacrylate (PMMA) materials, which are a soft polymer and suitable for microthermal machining. The probe of the SThM is heated and used as a machining tool on the PMMA material. Adjustment of the resistance can control the probe’s temperature. To obtain good machining quality, the probe temperature must be continuously controlled. The temperature of the machined area of the sample’s surface must be higher than the melting point of the PMMA material. However, a lower machined quality occurs when the probe temperature is too high. Furthermore, the adhesive phenomenon is very apparent when the contact mode is used in SThM machining. The microthermal machining of PMMA materials using SThM in semi-contact mode at a probe temperature of 400 °C has the best results. The technique can be used to process a complicated pattern and applied for use of high-density data storage. 相似文献
Direct laser machining and electrospinning are utilized to obtain a bi‐layered hybrid scaffold with hierarchical topographical features to mimic extracellular matrix‐like microenvironment of cells. Adult bone marrow derived human mesenchymal stem cells (hMSCs) are cultured in vitro in these hybrid scaffolds, and cell orientation, proliferation, viability, and differentiation are evaluated. The results show that this novel hybrid scaffold not only supports cell growth like traditional scaffolds, but also elicits positive responses from the cells, like lineage commitment and alignment, which are essential features of future scaffolds.
A uniform and continuous chromized coating on AISI 1020 steel is produced by low-temperature pack chromization (LTPC) with electrical discharge machining and Ni electroplating pretreatments. The anticorrosive performance of the chromized steels is investigated in a 0.5 M H2SO4 solution at room temperature. The testing results indicate that the chromized specimen with electrical discharge machining and Ni electroplating pretreatments exhibits the lowest corrosion current density, 2.16 × 10−8 A cm−2, among the tested specimens. The corrosion resistance of all tested specimens are in the order of bare 1020 < 1020-Cr(700-2) < 1020-Ni-Cr(700-2) < 1020-EDM-Ni-Cr(700-2). Moreover, the 1020-Ni-Cr(700-2) specimen have the best conductivity as a result of the less amount of oxides in the superficial coating. 相似文献