科研之友
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摘要
For the scribing-to-severing method, it is difficult to sever single-crystal SiC and sapphire without edge fracture and near-zero material removal due to material hardness, brittleness and crystal orientation. According to the micron-scale brittle behavior, a crack-free microgroove-apex is proposed on single-crystal SiC and sapphire surfaces to induce the micro-crack propagation. The objective is to understand how the ductile-to-brittle behavior and crystal orientation to influence the severing performance. In order to induce the micro-crack propagation in severing, the microgroove-apex was machined on the workpiece surface by the micro-grinding. First, the micro-indentation experiments were performed to explore the ductile-to-brittle behavior; then, the severing force, efficiency and accuracy were investigated in severing experiments, respectively. It is shown that the micro-crack propagation ratio derived from the micro-indentation may display the ductile-to-brittle behavior in relation to the severing performance. With larger harness and less micro-crack propagation ratio, the 4H-SiC leads to larger severing force, longer severing time and less form error than the sapphire does, respectively. Moreover, the severing force and the severing time are sensitive to the crystal orientation. Because the micro-crack propagation behavior is changed by the loading rate, the static severing is transferred to the dynamic severing at the critical loading rate, thus leading to different severing behavior. Along an accurate micro-crack propagation, the precision severing depends on a sharpness and smoothness microgroove-apex.
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单位上海交通大学
