Material Selection Guide (mechanical)
Common engineering materials at a glance
| Material | Density g/cm³ | Strength (MPa) | E-modulus (GPa) | Typical use / notes |
|---|---|---|---|---|
| Aluminium 6061-T6 | 2.70 | 276 (Sy) | 69 | Excellent machinability; general structural, brackets, enclosures |
| Aluminium 7075-T6 | 2.81 | 503 (Sy) | 72 | High strength-to-weight; aerospace, but poor weldability |
| Steel A36 | 7.85 | 250 (Sy) | 200 | General structural shapes and plates; weldable |
| Steel 1045 (as-rolled) | 7.85 | ~450 (Sy) | 205 | Shafts, axles, gears when heat treated |
| Steel 4140 (Q&T) | 7.85 | ~655–1200 (Sy, by temper) | 205 | High-strength machine parts, shafts, tooling |
| Stainless 304 | 8.00 | 215 (Sy) | 193 | Corrosion resistance, food/pharma; work-hardens when machined |
| Stainless 316 | 8.00 | 290 (Sy) | 193 | Better chloride/pitting resistance than 304 |
| Titanium 6Al-4V (Ti-64) | 4.43 | 880 (Sy) | 114 | Best strength/weight + corrosion; expensive, poor chip machining |
| Brass C360 (free-cutting) | 8.50 | ~205 (Sy) | 97 | Superb machinability; fittings, valve parts |
| Copper C110 | 8.94 | ~70 (Sy) | 117 | Electrical conductivity; soft — work hardens |
| Nylon 6/6 (dry) | 1.14 | ~83 (tensile) | 2.8 | Bearings, gears, bushes; absorbs moisture (changes properties) |
| Acetal (POM) | 1.41 | ~62 (tensile) | 2.6 | Low friction, precise machined plastic parts |
| ABS | 1.05 | ~40 (tensile) | 2.3 | 3D-print, housings; low heat resistance |
| GFRP (glass-fibre laminate) | ~1.9 | ~150–350 (tensile) | ~20–35 | Anisotropic — properties follow fibre direction |
Steel grades shown are representative. For load-bearing parts use the certified minimum properties of the exact specification (e.g. ASTM A36 vs A572-50 differ).
What is Material Selection Guide (mechanical)
Material Selection Guide (mechanical) is a quick-comparison table of the engineering materials a mechanical design reaches for most: density, representative strength, elastic modulus and the typical use each material serves. The fourteen rows span the metals — the aluminium alloys 6061-T6 and 7075-T6, the steels A36, 1045 and 4140, stainless 304 and 316, titanium 6Al-4V, brass C360 and copper C110 — and the engineering polymers and composites: nylon 6/6, acetal, ABS and glass-fibre laminate.
The columns answer the three questions every early material decision asks: how heavy is it, how strong is it, and how stiff is it. Aluminium 6061-T6 sits at 2.70 grams per cubic centimetre with a 276 MPa yield, steel A36 at 7.85 with 250, titanium 6Al-4V at 4.43 with 880 — the strength-to-weight champion on the table — and the polymers below 1.5 with tensile strengths in the tens of megapascals. The modulus column separates the families: steels near 200 GPa, aluminiums near 70, titanium at 114, and the polymers at 2 to 3, which is why a plastic part must be proportioned so differently from a metal one.
How to Use Material Selection Guide (mechanical)
- Step 1: Screen by the dominant requirement first. If weight drives the design, compare the density column — aluminium at 2.70 and titanium at 4.43 against steel at 7.85. If corrosion drives it, the stainless and titanium rows carry that in their use notes.
- Step 2: Check the strength column against the load. The value is the yield strength for the metals and tensile strength for the polymers; note that the 4140 row shows a range because its yield depends on temper.
- Step 3: Check the modulus column for stiffness-critical parts. A shaft or beam that must not deflect needs the high-modulus families — steel, stainless, titanium — while a snap-fit housing can work in acetal at 2.6 GPa with the right geometry.
- Step 4: Use the search box to filter the table to one material family while comparing candidates side by side, or to find which row carries a property you need.
- Step 5: Verify against the material specification before release: the values are typical published figures for the most common condition, and certified minimums from the exact ASTM or ISO spec — A36 versus A572-50, for example — are what a load-bearing part must be checked against.
Why Use Material Selection Guide (mechanical)
Material selection mistakes rarely fail the obvious way — the wrong family is usually caught by weight or corrosion. They fail on the less visible axes: a part designed in steel proportions copied into aluminium without accounting for the third of the modulus, or a strength quoted from a heat-treat datasheet that the specified condition never reaches. A table that puts density, strength and modulus side by side for the standard conditions makes those comparisons explicit before the geometry is locked.
The table is equally a reminder of what each material costs in design terms beyond price: 7075-T6 gives high strength but poor weldability, 304 work-hardens when machined, titanium is expensive and chips poorly, nylon absorbs moisture and changes properties, and glass-fibre laminate is anisotropic — its properties follow the fibre direction. The use notes carry those caveats so the selection considers manufacturability and environment, not just the numbers in the first three columns.
Privacy & Security
This tool runs entirely in your browser — no data ever leaves your device. There is no server round-trip, no upload, no logging, and no account required. Your input is processed locally using client-side JavaScript and is never stored, transmitted, or accessible to anyone else. When you close the tab, everything disappears.
Frequently Asked Questions
Why does 4140 show a strength range while A36 shows a single value?
Because A36 is a structural steel sold in the as-rolled condition with a certified minimum yield near 250 MPa, while 4140 is a medium-carbon alloy steel whose strength is set by heat treatment — the same bar can be delivered with a yield anywhere from roughly 655 MPa in a modest quench-and-temper up to about 1200 MPa at a higher temper. The range is the material's capability envelope; the actual number depends on the heat-treat specification on the drawing.
When is titanium worth its cost?
When strength-to-weight and corrosion resistance are required together and nothing cheaper will do. At 4.43 grams per cubic centimetre with an 880 MPa yield, titanium 6Al-4V beats steel on strength per unit weight by a wide margin while resisting the chloride attack that would force an expensive stainless or a coating on a steel part. The cost shows up in the material price and in machining — titanium is expensive and chips poorly — so the aerospace, marine and medical applications that justify it are the ones where a kilogram saved or a corrosion failure avoided is worth real money.
Why is aluminium much less stiff than steel even pound for pound?
Stiffness is set by the elastic modulus, and aluminium's is about 69 GPa against steel's 200 — roughly a third. Since modulus does not scale with strength or weight, an aluminium replacement for a steel part must be proportioned for roughly three times the section to resist the same deflection, which is why aluminium parts in stiffness-critical roles end up chunky despite being light. For strength-limited parts the comparison is kinder — 6061-T6 at 276 MPa yield holds up far better against A36 than the modulus comparison suggests.
How should I read the polymer strength values?
The polymer rows report tensile strength rather than yield, and the values — roughly 83 MPa for dry nylon 6/6, 62 for acetal, 40 for ABS — come with conditions attached. Nylon absorbs moisture and its properties change as it does, so the dry value is optimistic in a humid environment. Polymer strength also depends on temperature, strain rate and how the part is moulded, and the table's modulus values in the 2 to 3 GPa range are the reminder that plastics are for geometry-rich, lightly loaded parts, not substitutes for structural metal.