1 / 18

Day 11 – Intermetallic compounds and the Iron-Carbon Phase diagram

Day 11 – Intermetallic compounds and the Iron-Carbon Phase diagram. Note the MG2Pb line. Intermetallic compounds show up as vertical lines. Their bonding predicts that they will be hard britlle , “rock-like” phases. f20_09_pg284. f24_09_pg290.

lindley
Download Presentation

Day 11 – Intermetallic compounds and the Iron-Carbon Phase diagram

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. Day 11 – Intermetallic compounds and the Iron-Carbon Phase diagram

  2. Note the MG2Pb line. Intermetallic compounds show up as vertical lines. Their bonding predicts that they will be hard britlle, “rock-like” phases f20_09_pg284

  3. f24_09_pg290

  4. Austenite (g). High temperature form of Fe – not in equilibrium below 727C. It is FCC. Can hold up to 2.14% C by weight. This is also very soft ductile material. Cementite (Fe3C). A compound of Fe and C which always has 6.70% C by weight. The crystal structure is complicated. It is very hard brittle material. Ferrite (a) Low temperature form of Fe – it is BCC. Can only hold up to 0.022% C by weight. This carbon is interstitial. It is very soft ductile material. f24_09_pg290

  5. Vocabulary • Ferrite (a) Low temperature form of Fe – it is BCC. Can only hold up to 0.022% C by weight. This carbon is interstitial. It is very soft ductile material. • Austenite (g). High temperature form of Fe – not in equilibrium below 727C. It is FCC. Can hold up to 2.14% C by weight. This is also very soft ductile material. • Cementite (Fe3C). A compound of Fe and C which always has 6.70% C by weight. The crystal structure is complicated. It is very hard brittle material.

  6. f26_09_pg293

  7. Using the Fe-C Diagram • We can use the diagram to predict microstructure, and thereby mechanical properties in equilibrium (i.e. slow) cooled steels. • This depends on a reaction known as the Euctectoid Reaction. Here is that reaction As we cool below 727C The resulting microconstituent is called Pearlite, P.

  8. Pearlite • Here are some micrograph images.

  9. f27_09_pg294

  10. f28_09_pg295

  11. Hypoeutectoid – Below Eutectoid Composition, i.e. less than 0.77% carbon. • Hypereutectoid – Above Eutectoid Composition, i.e. greater than .77% carbon

  12. f29_09_pg295

  13. f30_09_pg296

  14. Finding the Relative Amount of Pearlite • Steel has 0.30% C by wt. Use the Fe-C diagram to predict microstructure if we cool it slowly. WP at low temp = Wg at 727 0.30 %C

  15. f31_09_pg297

  16. f32_09_pg298

  17. f33_09_pg299

  18. What is steel? • A vast family of materials • Usually composed of ferrite + cementite. There are some exceptions. • The way that the cementite is distributed in the ferrite is very important. For example, • Very coarse roundish cementite particles widely separated  soft ductile steel. • Very fine roundish cementite particles closely spaced  hard strong steel. (Has some ductility) • And so on – there are many ways to distribute cementite in ferrite.

More Related