1 / 20

Microstructure Evolution of Semi-solid Magnesium Alloy AZ91D Under Electric Current

Microstructure Evolution of Semi-solid Magnesium Alloy AZ91D Under Electric Current. Y Yang , Q Zhou, J Tang, Z Hu Institute of Metal Research Chinese Academy of Sciences. 2ed Sino-German Workshop on EPM, 16-19 Oct. 2005, Dresden, Germany. Outline. Introduction Experimental procedure

deo
Download Presentation

Microstructure Evolution of Semi-solid Magnesium Alloy AZ91D Under Electric Current

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Microstructure Evolution of Semi-solid Magnesium Alloy AZ91D Under Electric Current Y Yang, Q Zhou, J Tang, Z Hu Institute of Metal Research Chinese Academy of Sciences 2ed Sino-German Workshop on EPM, 16-19 Oct. 2005, Dresden, Germany

  2. Outline • Introduction • Experimental procedure • Results • Dendritic growth • Current pulse density • Current pulse duration • Discharging cycle • Treating time • Nondendritic particle size • Thermal fluctuation • Conclusions

  3. The most lightest structural alloy • Anti-vibration Introduction • Magnesium alloy offers numerous merits in physical, mechanical and casting properties.

  4. Usages of magnesium alloy • Magnesium alloy to near-net­shape will find widespread application in auto-, video-, computer- and communication- equipment, combined with the on-going ‘light-weighting’ of components.

  5. Typical dendrites in magnesium AZ91D casting

  6. Dendrites in AZ91D solidified with Low-Voltage Electric Current Pulses method (LVECP)

  7. Experimental Schematics of experimental setup

  8. density time duration discharging cycle Pulse current density curve • Parameters: • Current pulse density: 0, 1.3, 3, 4.3, 5.2 kA/cm2 • Current pulse duration: 0, 0.6, 1.0, 1.2, 1.5 ms • Discharging cycle: 0, 4, 6, 8, 10, 12 sec • Treating time: 0, 5, 10, 15, 20 min

  9. Experimental Material Compositions of the AZ91D alloy (wt.％) Commercial AZ91D alloy Liquidus temperature: 595 oC Solidus temperature: 470 oC

  10. 1 kA/cm2 3 kA/cm2 4 kA/cm2 5 kA/cm2 Effect of current pulse density on dendrite growth (a) Big dendrites; (b) small dendrites; (c) globular and cosh-shaped. (d) nondendritic, equiaxed paticles.

  11. 0.6 ms 1.0 ms 1.2 ms 1.5 ms Effect of current durationon dendrite growth (a) Dendrites with long primary arms; (b, c) rosette-shaped. (d) globular and cosh-shaped.

  12. 6 sec 8 sec 10 sec 12 sec Effect of discharging cycle on dendrite growth (a) globular and cosh-shaped; (b, c) rosette-shaped; (d) dendritic structure.

  13. 5min 10min 15min 20min Effect of treating time on dendrite growth The shape of the primary grains from dendritic to rosette-shaped then nondendritic with increasing treating time.

  14. Non-dendritic particle size

  15. Distribution of non-dendritic particle size The average size of the particles is about 150 m

  16. Thermal fluctuation during solidification • Thermal history of specimen The temperature of the sample with current pulse treatment is higher after treating time exceeds 20 minutes due to Joule heating. • Temperature fluctuation The temperature fluctuation increases as the current density increases. The maximal temperature fluctuation is about 16 oC.

  17. Root remelting of dendrite arm

  18. Schematic illustration of dendrite evolution (a) initial dendritic (b) shrinkage of secondary arm roots (c) remelting and detaching of secondary arm roots (d) detaching finished

  19. Conclusions • The morphology of primary phase is transited from dendritic to nondendritic, equiaxed particles by Low-voltage Electric Current Pulses during solidification of AZ91D alloy. • The particle size of AZ91D alloy decreases with increase of the current pulse density, discharging cycle, and treating time; but increases with increasing the current pulse duration. • Heat generation caused by Joule heating during discharge causes temperature fluctuation and decreases the cooling rate of solidification. • Electric current pulse restrains growth of the dendrites, makes dendrite arms remelted and attached during solidification, which leads to formation of nondendritic, equiaxed structure.

  20. Thank you for your attention

More Related