ELEKTRON AZ91D magnesium die-casting alloy, as cast; Magnesium Elektron datasheet 475 (7/01), typical properties; Poisson from MIL-HDBK-5J for AZ91C castings.
SAC305 (Sn96.5Ag3.0Cu0.5) solder alloy, bulk; Indium Corporation Indalloy 256 (SAC305) for Preforms product data sheet (Form No. 100346 R0, 2024), selected properties, test temperature not stated; expansion and specific heat from MacDermid Alpha VACULOY SAC TDS (06 September 2023).
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.
Questions
Is Magnesium AZ91D stronger than Solder SAC305?
Magnesium AZ91D is stronger: its yield strength is 150 MPa against 22 MPa for Solder SAC305 (6.82x).
Which is lighter, Magnesium AZ91D or Solder SAC305?
Magnesium AZ91D is lighter: 1,810 kg/m³ against 7,350 kg/m³ for Solder SAC305.
Which is stiffer, Magnesium AZ91D or Solder SAC305?
Magnesium AZ91D is stiffer: Young's modulus 45 GPa against 6.9 GPa for Solder SAC305, so the same part in Magnesium AZ91D deflects less under the same load.
Which is lighter for the same job, Magnesium AZ91D or Solder SAC305?
For the same stiffness or strength: Magnesium AZ91D 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
Magnesium AZ91D
Solder SAC305
Stiff rod or tie (tension)
lighter
26.5x heavier
Stiff beam (bending)
lighter
10.4x heavier
Stiff panel or plate
lighter
7.59x heavier
Strong rod or tie
lighter
27.7x heavier
Strong beam
lighter
14.6x heavier
Strong panel or plate
lighter
10.6x 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).
Which conducts heat better, Magnesium AZ91D or Solder SAC305?
Magnesium AZ91D conducts heat better: 72 W/m·K against 61 W/m·K for Solder SAC305.
Which expands less with temperature?
Solder SAC305 expands less: 21.9 µm/m·K against 25 µm/m·K for Magnesium AZ91D.