Multi-discharge EDM coring of single crystal SiC ingot by electrostatic induction feeding method

Highlights

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A novel tool electrode setup was developed for EDM coring of SiC ingot/wafer.

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EDM coring of 2 inch SiC ingot/wafer by rod electrode was carried out successfully.

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EDM by electrostatic induction feeding method was applied for rough machining.

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Multi-discharge EDM by electrostatic induction feeding method was developed.

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Multi-discharge EDM improves both the machining rate and the surface integrity.

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Abstract

A new technique of EDM coring of single crystal silicon carbide (SiC) ingot was proposed in this paper. Currently single crystal SiC devices are still of high cost due to the high cost of bulk crystal SiC material and the difficulty in the fabrication process of SiC. In the manufacturing process of SiC ingot/wafer, localized cracks or defects occasionally occur due to thermal or mechanical causes resulted from fabrication processes which may waste the whole piece of material. To save the part of ingot without defects and maximize the material utilization, the authors proposed EDM coring method to cut out a no defect ingot from a larger diameter ingot which has localized defects. A special experimental setup was developed for EDM coring of SiC ingot in this study and its feasibility and machining performance were investigated. Meanwhile, in order to improve the machining rate, a novel multi-discharge EDM coring method by electrostatic induction feeding was established, which can realize multiple discharges in single pulse duration. Experimental results make it clear that EDM coring of SiC ingot can be carried out stably using the developed experimental setup. Taking advantage of the newly developed multi-discharge EDM method, both the machining speed and surface integrity can be improved.

Keywords

• Electrical discharge machining (EDM); 
• EDM coring; 
• Multi-discharge EDM; 
• Single crystal silicon carbide (SiC); 
• Electrostatic induction feeding; 
• SiC wafer
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    • Soure:Sciencedirect
      
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Latent hardening effect under self- and coplanar dislocation interactions in Mg single crystals

Latent hardening experiments were carried out on Mg  single crystals under basal self- and coplanar dislocation interactions. For self-interactions the latent hardening ratio (LHR) is independent on the amount of primary deformation in the basal slip system. For coplanar interactions LHR increases linearly with primary strain and quadratically with primary stress, suggesting that during the stage A in Mg the coplanar slip systems harden proportionally to the dislocation density accumulated in the other coplanar slip system.

Keywords

• Magnesium single crystals; 
• Easy glide; 
• Basal slip; 
• Latent hardening; 
• Coplanar interactions
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  • Soure:Sciencedirect
    
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