Tutorial: steel, heat & structure

Build a short lecture the way the built-in sample does it — an Fe–C diagram driven by two sliders, the crystal underneath it, a tensile test beside it, and saved states to walk the room through the heat treatment.

The finished version of this deck ships with Quodra: open the dashboard, find Steel, Heat & Structure under the Material Science tag, and you get a copy to poke at. This tutorial builds a smaller one from a blank deck, so that every wire is one you made.

Allow about twenty minutes. You will need nothing you do not already have — no data files are required until the last section, and that one is optional.

1. The diagram#

Open a blank deck and add a phase diagram: press Y for the Matter Lab button on the insert toolbar, open its caret, and choose Phase diagram.

In the inspector, open the System menu and pick Fe–C (steel). The diagram fills in — regions, boundaries, the two invariant points, and a state point that lands where a tie line and a lever answer are immediately visible. Under the plot, the source line names what it is: a straight-segment approximation after Callister, with δ-ferrite omitted.

Leave Tie line, Lever rule and Labels on. The strip below the diagram now reads the region you are in, the lever fractions, and the state point's coordinates.

2. Two sliders#

Press P to add a parameter panel. Give it the title Alloy & furnace.

Set up the first variable to match the sample:

• name carbon_content, label carbon
• min 0.02, max 1.2, step 0.01, val 0.4
• unit wt%, Decimals 2

Press + Add variable and set up the second:

• name temperature, label temperature
• min 450, max 1550, step 1, val 728
• unit °C, Decimals 0

3. Wire them to the state point#

Still in the parameter panel's inspector, under carbon_content, find the Drives row and open Choose a value…. The menu lists every bindable slot on the deck, named object · slot with its unit. Pick Phase diagram · state point · carbon (wt%).

Do the same under temperature, picking Phase diagram · state point · temperature (°C).

Both directions now work. Move a slider and the state point moves; drag the state point and the sliders move with it, along with everything else those two parameters drive. The inspector's own number fields for the bound axes are replaced by driven by a parameter, because a field that accepted a number and then lost it to the binding would be a lie.

4. Read the eutectoid#

This is the slide to linger on in front of a room.

1. Set carbon_content to 0.76 — the eutectoid composition. The invariant point beside your state point is labelled eutectoid · 0.76 wt% · 727 °C.
2. Drag temperature slowly down from 800. Above the isotherm the read-out says γ (austenite); the moment you cross 727 °C it flips to α + Fe₃C, and the lever fractions appear.
3. Now set carbon_content back to 0.4 and put temperature at 728. You are in α + γ, and the strip shows the two fractions with the tie line drawn across the diagram.

The fractions are not decoration: each one carries the arithmetic that produced it, expressed in the phase compositions the tie line ends at.

Add a text object beside the diagram and type a sentence that reads its own inputs:

At {{temperature}} °C and {{carbon_content}} wt% C the diagram answers three
questions at once: which phases, in what proportions, of what composition.

Move either slider and the sentence keeps up.

5. The structure underneath#

Add a crystal on a new slide: press Y again — the crystal is what the button itself inserts.

Press Import… on the Structure row and choose a CIF, POSCAR or XYZ file for body-centred iron. The inspector reads back the formula, the lattice constants, the cell volume and the density; the sample's α-ferrite cell is cubic with a lattice constant of 2.8665 Å.

Then:

• open Supercell and set Repeat a, Repeat b and Repeat c to 2, so the packing is visible rather than implied;
• open Planes & directions, type 1 1 0 in the (hkl) box, and press Add — the slip plane draws clipped exactly to the cell;
• write a Caption saying what it is, for example α-ferrite · BCC · the (110) slip plane shown.

Double-click the crystal on the slide and drag it: the camera orbits, and it commits once when you let go. The wheel zooms while it is live and commits when the wheel goes quiet, so one gesture is one undo step.

6. What the customer feels#

Add a stress–strain object from the Matter Lab caret and press Import… on its Data row. It reads CSV, TSV, text and XLSX — two columns, strain then stress.

Check the chips under the curve: E, σy, UTS and εf. Hover one and the method comes with it. Open Derived properties for the full set — Young's modulus, 0.2% offset yield, Ultimate strength, Fracture strain, Resilience and Toughness — each with its method line, and a warning where the fit is shaky.

If the auto-detected elastic range picked the wrong window, type your own into Elastic fit from and Elastic fit to; both hold auto until you do. Set Stress unit to match your file, and leave Values on Engineering unless you mean the true-stress conversion, which warns that it is valid only to necking.

7. Save the states you will talk through#

Go back to the diagram, open Scientific states in its inspector, and save three:

1. Set the sliders to 0.4 and 450, type Room temperature into Save as, press Save.
2. Set them to 0.4 and 900, save Austenitized.
3. Set them to 0.76 and 728, save Eutectoid.

Each state captures every parameter on the deck by name, plus the diagram's own state point. The three names now appear as chips on the object. Click one and the deck glides there — the sliders ramp, the point travels, and everything bound to those parameters follows — as a single undo step.

8. Decide who may move what#

Open the parameter panel's inspector and, for each variable, open Who may move it:

• Presenting — Editable, Locked or Hidden.
• Audience — Editable or Locked on supported audience surfaces. The current shared-link viewer does not provide these controls or reactive recomputation.
• On re-entry — Keep value or Reset.

For this deck, leave both sliders editable while presenting, and set On re-entry to Reset so a repeated demo always starts from the same place.

9. Check the wiring before you speak#

Open any Matter inspector's Workspace row, press Open Matter Lab, and press Connections in the header. You should see both parameters listed with what they drive: → phase-diagram · state point · carbon (wt%) and the temperature equivalent, plus a ⇢ line for the text object that reads them by name.

Anything wrong shows here rather than mid-talk: a unit that does not match, a slot the object no longer offers, or a slider that drives nothing and that nothing reads. Press Done to return to the deck — nothing was copied, so nothing needs saving.

10. Present it#

Press Present (full screen). Everything stays live: the sliders move, the state point tracks them, the lever fractions update, and the state chips glide the room from room temperature to austenitized to the eutectoid. On a plot, ← and → walk the data itself, ⇧ steps ten at a time, and Esc clears the read-out.

Where to go next#

• The object types — the seven objects this tutorial did not use.
• Datasets & instrument files — what happened to the files you imported.
• Presenting — the presenter view, notes and ink.