Does heat treatment change the modulus of elasticity?

No. Heat treatment changes yield strength, tensile strength and hardness dramatically, but the modulus of elasticity moves by less than 1%. Stiffness comes from atomic bonding, which alloying and heat treatment do not change. A hardened and an annealed steel bar of the same size deflect the same amount under the same load.

Why does carbon steel have the same modulus as stainless?

Because both are iron-based with the same metallic bonding, and stiffness depends on the strength of those bonds rather than on the alloying elements. Stainless is slightly lower — 193 GPa against 205 — because the austenitic structure is a little less stiff, but the difference is under 6%.

What is a typical yield strength for steel?

It ranges from about 215 MPa for annealed austenitic stainless to over 1,700 MPa for hardened bearing steel — a factor of eight. The tensile strength ranges similarly. The modulus, by contrast, sits between 193 and 210 GPa for every one of them.

Why is the plastic modulus lower than steel's?

Plastics are held together by weak secondary bonds between long-chain molecules, rather than by metallic bonds. Nylon's modulus is 2.8 GPa against steel's 205 — about 1.4%. That is why a plastic part of the same shape deflects roughly 70 times as much as a steel one under the same load, which is usually the governing design limit for plastic parts.

Why is aluminium more expensive than steel for the same strength?

Because its modulus is a third of steel's, so a deflection-limited part needs roughly three times the section — and aluminium is also more expensive per kilogram. Where weight is not the constraint, steel wins. Where it is, aluminium's density of 2.70 against steel's 7.85 gives a three-fold advantage that can more than offset the section penalty.

Does gray iron have a yield strength?

No. Gray iron is brittle and fails in tension without yielding, so it is specified by tensile strength alone and the yield column shows a dash. Its compressive strength is three to four times its tensile strength, which is why it works well in machine bases and poorly in tension members.

Stress-Strain Properties

Modulus, yield and tensile strength, elongation and Poisson's ratio for 28 metals and plastics, with the two ratios that govern most design decisions.

Data verified 2026-09-29 · based on ASTM E8/E8M-22

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Mechanical Properties by Material

Material^[4]	Class^[4]	Modulus E GPa^[4]	Modulus E Msi^[3]	Yield strength MPa^[4]	Tensile strength MPa^[4]	Elongation %^[4]	Poisson's ratio^[4]	Density g/cm³^[4]	Note^[4]
AISI 1018 steel #	Carbon steel	205	29.73	370	440	25	0.29	7.87	Low-carbon baseline; the modulus every steel shares to within a few percent
AISI 1045 steel #	Carbon steel	205	29.73	530	625	12	0.29	7.85	Medium carbon; the yield-to-tensile gap narrows as carbon rises
AISI 4140 steel (Q&T) #	Alloy steel	205	29.73	655	1020	18	0.29	7.85	Quenched and tempered; a typical 150 ksi-class alloy steel
AISI 4340 steel (Q&T) #	Alloy steel	205	29.73	1170	1280	12	0.29	7.85	Higher-strength Q&T condition; note that the modulus is unchanged
AISI 52100 (hardened) #	Bearing steel	210	30.46	1700	2000	2	0.30	7.81	Through-hardened bearing steel; very high strength, very low ductility
AISI 304 stainless #	Stainless	193	27.99	215	505	40	0.29	7.9	Austenitic; low yield, high elongation, no sharp yield point
AISI 316 stainless #	Stainless	193	27.99	205	515	40	0.30	8	Molybdenum-bearing austenitic; nearly identical mechanical properties to 304
17-4 PH stainless (H900) #	Stainless	196	28.43	1170	1310	10	0.27	7.8	Precipitation hardened; strength comparable to alloy steel at 10% elongation
D2 tool steel (hardened) #	Tool steel	210	30.46	1530	1930	2	0.30	7.7	High-chromium cold-work steel; fails with almost no plastic deformation
H13 tool steel (hardened) #	Tool steel	210	30.46	1380	1580	9	0.30	7.8	Hot-work steel; toughness retained at strength, unlike D2
Gray iron Class 30 #	Cast iron	100	14.50	—	214	0.5	0.26	7.2	No yield point — it is brittle and fails in tension without warning
Ductile iron 65-45-12 #	Cast iron	169	24.51	310	448	12	0.28	7.1	Nodular graphite gives real ductility that gray iron does not have
Aluminium 6061-T6 #	Aluminium	68.9	9.99	276	310	12	0.33	2.7	The general-purpose structural aluminium alloy
Aluminium 7075-T6 #	Aluminium	71.7	10.40	503	572	11	0.33	2.81	Highest strength of the common aluminium alloys
Aluminium 2024-T4 #	Aluminium	73.1	10.60	324	469	20	0.33	2.78	Aerospace alloy; better fatigue resistance than 7075
Aluminium 5052-H32 #	Aluminium	70.3	10.20	193	228	12	0.33	2.68	Non-heat-treatable; excellent corrosion resistance and formability
Magnesium AZ31B #	Magnesium	45	6.53	200	260	15	0.35	1.77	The lightest structural metal; modulus is only 22% of steel's
Titanium Ti-6Al-4V #	Titanium	113.8	16.51	880	950	14	0.34	4.43	The workhorse titanium alloy; strength of alloy steel at 57% of the density
Titanium Grade 2 (CP) #	Titanium	102.7	14.90	275	345	20	0.34	4.51	Commercially pure; formable and corrosion resistant but not strong
Inconel 718 (aged) #	Superalloy	200	29.01	1030	1240	12	0.29	8.19	Nickel superalloy; keeps its strength where steel would creep
Copper C11000 (annealed) #	Copper	117	16.97	69	220	45	0.34	8.94	Very ductile and low strength; the electrical reference metal
Brass 360 (half hard) #	Copper alloy	97	14.07	310	385	20	0.31	8.5	Free-machining brass; strength well below steel at similar density
Nylon 6/6 (dry) #	Plastic	2.8	0.41	82.7	82.7	40	0.39	1.14	Modulus is 1.4% of steel's — the whole story of why plastics deflect
Acetal (POM-H) #	Plastic	3.1	0.45	75.8	75.8	25	0.35	1.42	Stiff and dimensionally stable for a plastic
PEEK (unfilled) #	Plastic	3.6	0.52	100	100	45	0.38	1.3	The stiffest of the common unfilled engineering plastics
Polycarbonate #	Plastic	2.4	0.35	62	66	110	0.37	1.2	Very high elongation; tough rather than strong
Acrylic (PMMA) #	Plastic	3.1	0.45	72	72	4.5	0.35	1.19	Strong and stiff for a plastic, and brittle — only 4.5% elongation
PTFE (unfilled) #	Plastic	0.55	0.08	25	25	350	0.46	2.16	The lowest modulus of any engineering plastic; it cold-flows under load

Yield strength depends on the alloy and the heat treatment; modulus does not. That single fact governs a great deal of materials selection, and it is the reason the modulus column in this table has far less variation than the strength columns.

Gray iron shows a dash in the yield column because it has none — it is brittle and fails in tension without yielding, so it is specified by tensile strength alone. Values are typical for the condition stated; yield and tensile strength for a given alloy vary widely with temper, section size and product form, and the material data sheets on this site give the ranges.

Modulus, Poisson's ratio and density are the three elastic constants here — they describe how a material deforms below yield and are essentially independent of heat treatment. Yield, tensile and elongation are strength properties and change completely with it.

The Modulus Is the Same for Every Steel

Carbon steel, alloy steel, tool steel, stainless steel and bearing steel all have a modulus between 193 and 210 GPa. Switching from 1018 to 4340 raises the yield strength by a factor of three and changes the modulus by nothing measurable.

The physical reason is that stiffness comes from the strength of the atomic bonds, which are the same iron-iron bonds in every steel. What alloying and heat treatment change is how easily whole planes of atoms slide past one another — the plastic behaviour, not the elastic one.

The design consequence is direct and often missed. If a part is limited by deflection, no steel will help; the answer is more section, or a material with a genuinely higher modulus such as tungsten or beryllium. If a part is limited by yielding or fatigue, a stronger steel helps a great deal. Deciding which limit governs is the first step in any materials selection, and it is the step that is most often skipped.

Reading a Stress-Strain Curve

The elastic region is a straight line whose slope is the modulus. It ends at the yield point, where the curve bends over and the material starts to deform permanently — everything past that point is unrecoverable.

Three shapes are worth recognising. Mild steel shows a distinct yield plateau and an upper and lower yield point, which is an artefact of interstitial carbon rather than a fundamental property; the value tabulated is the lower yield strength. Austenitic stainless has no yield point at all — the curve bends over gradually, so a proof stress is quoted instead, usually the 0.2% offset value. Cast iron and hardened tool steel fracture while the curve is still rising, essentially without plastic deformation.

The area under the curve is toughness — the energy absorbed before fracture. Note that a high-strength material is not necessarily tough: 52100 bearing steel at 2,000 MPa tensile has only 2% elongation, and the area under its curve is small. Tool steel at 1,930 MPa tensile with 2% elongation is strong and brittle, while Inconel 718 at 1,240 MPa with 12% elongation is both strong and tough. Tensile strength alone does not tell you which.

Frequently Asked Questions

Does heat treatment change the modulus of elasticity?: No. Heat treatment changes yield strength, tensile strength and hardness dramatically, but the modulus of elasticity moves by less than 1%. Stiffness comes from atomic bonding, which alloying and heat treatment do not change. A hardened and an annealed steel bar of the same size deflect the same amount under the same load.
Why does carbon steel have the same modulus as stainless?: Because both are iron-based with the same metallic bonding, and stiffness depends on the strength of those bonds rather than on the alloying elements. Stainless is slightly lower — 193 GPa against 205 — because the austenitic structure is a little less stiff, but the difference is under 6%.
What is a typical yield strength for steel?: It ranges from about 215 MPa for annealed austenitic stainless to over 1,700 MPa for hardened bearing steel — a factor of eight. The tensile strength ranges similarly. The modulus, by contrast, sits between 193 and 210 GPa for every one of them.
Why is the plastic modulus lower than steel's?: Plastics are held together by weak secondary bonds between long-chain molecules, rather than by metallic bonds. Nylon's modulus is 2.8 GPa against steel's 205 — about 1.4%. That is why a plastic part of the same shape deflects roughly 70 times as much as a steel one under the same load, which is usually the governing design limit for plastic parts.
Why is aluminium more expensive than steel for the same strength?: Because its modulus is a third of steel's, so a deflection-limited part needs roughly three times the section — and aluminium is also more expensive per kilogram. Where weight is not the constraint, steel wins. Where it is, aluminium's density of 2.70 against steel's 7.85 gives a three-fold advantage that can more than offset the section penalty.
Does gray iron have a yield strength?: No. Gray iron is brittle and fails in tension without yielding, so it is specified by tensile strength alone and the yield column shows a dash. Its compressive strength is three to four times its tensile strength, which is why it works well in machine bases and poorly in tension members.

Value Sources

Each data column on this page is tied to the source it came from. The numbers in square brackets correspond to the table headers above.

#	Source	Type	Revision / method
[1]	ASTM D638 — Standard Test Method for Tensile Properties of Plastics	standard	ASTM D638-22
[2]	ASTM E8/E8M — Standard Test Methods for Tension Testing of Metallic Materials	standard	ASTM E8/E8M-22
[3]	Value computed from the standard's defining relationship	derived	Computed at build time from the defining formula and verified against every row.
[4]	Published handbook mechanical properties for engineering materials	standard	compilations as published 2024–2026

Data Sources

Standard	Revision	What it covers on this page
ASTM E8/E8M — Tension Testing of Metallic Materials	ASTM E8/E8M-22	the metal property values and how they are measured
ASTM D638 — Tensile Properties of Plastics	ASTM D638-22	the polymer property values
Published handbook mechanical properties	compilations as published 2024–2026	every value in the table

Cross-checked against:

Strength values checked against the material data sheets already published on this site where they overlap
The steel modulus cross-checked across five different steel families to confirm it does not vary with alloy
The GPa-to-Msi conversion recomputed at build time for every row
Seven values held as known-value checks covering steel, aluminium, titanium, stainless and plastic

Derived values — the following values on this page are calculated, not taken directly from the standard:

Value	How it is derived
Modulus in Msi	GPa × 0.145037738, exact. Recomputed at build time for every row.

Values are typical for the condition stated, at room temperature. Yield and tensile strength vary widely with temper, section size and product form — the material data sheets on this site give the ranges. Modulus, Poisson's ratio and density are far more stable and are the values to rely on for deflection and stiffness work.

Accuracy and use. The values on this page are compiled from the published standards and cross-checked sources listed above. Where values are derived, the derivation is stated. No warranty, express or implied, is made as to the accuracy or completeness of this information, and no liability is accepted for any loss or damage arising from its use. Engineering reference data is provided for guidance in preliminary work — before a value is used for design, fabrication or acceptance testing, verify it against the current revision of the governing standard and against your own inspection. The user assumes all risk and responsibility in connection with the use of this information.

Cite This Page

Every value on this page is traceable to the sources listed above. If you use the data in a document, paper or report, cite it as:

Plain text

Engineering Reference. "Stress-Strain Properties Chart." https://refmanual.com/charts/stress-strain/ (accessed 2026-09-29). Data from ASTM E8/E8M — Tension Testing of Metallic Materials, ASTM E8/E8M-22.

BibTeX

@misc{stress-strain,
  title        = {Stress-Strain Properties Chart},
  author       = {{Engineering Reference}},
  howpublished = {\url{https://refmanual.com/charts/stress-strain/}},
  note         = {Accessed: 2026-09-29},
  source       = {ASTM E8/E8M — Tension Testing of Metallic Materials, ASTM E8/E8M-22}
}

RIS (EndNote, Zotero, Mendeley)

TY  - ELEC
TI  - Stress-Strain Properties Chart
AU  - Engineering Reference
PB  - Engineering Reference
UR  - https://refmanual.com/charts/stress-strain/
PY  - 2026
DA  - 2026-09-29
N1  - Source: ASTM E8/E8M — Tension Testing of Metallic Materials, ASTM E8/E8M-22
ER  -

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