6061-T6/T651, Kaiser Aluminum typical properties; Poisson from MIL-HDBK-5J
Ultimaker TPU 95A, 3D-printed specimens, XY (flat); Ultimaker S5 Pro, engineering intent profile, 0.15 mm layer height, AA 0.4 print core, 100% infill, Cura 4.9, printed one-at-a-time, conditioned >=24 h at room temperature. TDS (file v5.00), April 29, 2022.
Every value links to the document that states it. "Not sourced" means no citable source states it (or only a specification minimum); figures computed from it are left out too.
Plastic TPU is 3D printed: its properties depend on build direction and print settings; these are typical values.
Questions
Is Aluminum 6061-T6 stronger than Plastic TPU?
Aluminum 6061-T6 is stronger: its yield strength is 276 MPa against tensile strength 23.7 MPa for Plastic TPU (11.6x).
Which is lighter, Aluminum 6061-T6 or Plastic TPU?
Plastic TPU is lighter: 1,220 kg/m³ against 2,700 kg/m³ for Aluminum 6061-T6.
Which is stiffer, Aluminum 6061-T6 or Plastic TPU?
Aluminum 6061-T6 is stiffer: Young's modulus 68.3 GPa against 0.067 GPa for Plastic TPU, so the same part in Aluminum 6061-T6 deflects less under the same load.
Which is lighter for the same job, Aluminum 6061-T6 or Plastic TPU?
For the same stiffness or strength: Aluminum 6061-T6 is lighter for a stiff rod or tie (tension), stiff beam (bending), stiff panel or plate, strong rod or tie, strong beam, strong panel or plate.
Part that must be
Aluminum 6061-T6
Plastic TPU
Stiff rod or tie (tension)
lighter
461x heavier
Stiff beam (bending)
lighter
14.4x heavier
Stiff panel or plate
lighter
4.55x heavier
Strong rod or tie
lighter
5.26x heavier
Strong beam
lighter
2.32x heavier
Strong panel or plate
lighter
1.54x heavier
For the same stiffness or strength, mass scales with density over stiffness (or strength) raised to a power set by how the part is loaded: 1 for a rod in tension, 1/2 for a beam in bending, 1/3 for a panel (the standard material-selection indices).