Materials / Compare

Magnesium AZ91D vs. Stainless Steel 17-4PH

Compare Magnesium AZ91D vs. Stainless Steel 17-4PH strength, stiffness, weight and thermal properties.

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Magnesium AZ91DCast
Stainless Steel 17-4PHWrought
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Mechanical
Yield strength150MPasourcetypical, 0.2% tensile yield, ambient temperature1,275MPasourcetypical, transverse, sheet/strip
Ultimate tensile strength230MPasourcetypical, ambient temperature1,379MPasourcetypical, transverse, sheet/strip
Elongation at break3%sourcetypical, ambient temperature9%sourcetypical, transverse, in 2 in. (50.8 mm)
Young's modulus (stiffness)45GPasourcetypical197GPasourceH 900
Density1,810kg/m³sourcetypical7,800kg/m³sourceH 900
Strength to weight82.9kN·m/kg163kN·m/kg1.97x higher
Stiffness to weight24.9MN·m/kg25.3MN·m/kg2% higher
Poisson's ratio0.35sourcebase material: AZ91C casting (MIL-HDBK-5J handbook physical constant)0.272sourceH 900 (column)
Shear modulus16.7GPa77.4GPa4.65x stiffer in shear
Bulk modulus50GPa144GPa
Speed of sound4,986m/s5,026m/s
Thermal
Thermal conductivity72W/m·Ksourcetypical17.9W/m·Ksourceat 149 °C (300 °F), H 900
Thermal expansion25µm/m·Ksourcetypical, temperature range not stated10.8µm/m·Ksourcemean, 21–93 °C (70–200 °F), H 900
100 mm part over a 50 °C swing125µm growth54µm growth2.31x less
Specific heat1,050J/kg·Ksourcetypical460J/kg·Ksourcemean, 0–100 °C, H 900
Heats up and cools (diffusivity)37.9mm²/s7.59x faster4.99mm²/s
Thermal shock resistance6,240W/m7,809W/m25% more resistant
Melting point470–595°Csourcemelting rangenot sourced
Max service temperaturenot sourced316°Csourcestrength-retention limit (not oxidation)
Values forELEKTRON AZ91D magnesium die-casting alloy, as cast; Magnesium Elektron datasheet 475 (7/01), typical properties; Poisson from MIL-HDBK-5J for AZ91C castings.Cleveland-Cliffs 17-4 PH, Condition H 900, sheet/strip, transverse (Product Data Bulletin, May 2021)

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 Stainless Steel 17-4PH?

Stainless Steel 17-4PH is stronger: its yield strength is 1,275 MPa against 150 MPa for Magnesium AZ91D (8.5x).

Which is lighter, Magnesium AZ91D or Stainless Steel 17-4PH?

Magnesium AZ91D is lighter: 1,810 kg/m³ against 7,800 kg/m³ for Stainless Steel 17-4PH.

Which is stiffer, Magnesium AZ91D or Stainless Steel 17-4PH?

Stainless Steel 17-4PH is stiffer: Young's modulus 197 GPa against 45 GPa for Magnesium AZ91D, so the same part in Stainless Steel 17-4PH deflects less under the same load.

Which is lighter for the same job, Magnesium AZ91D or Stainless Steel 17-4PH?

For the same stiffness or strength: Magnesium AZ91D is lighter for a stiff beam (bending), stiff panel or plate, strong beam, strong panel or plate; Stainless Steel 17-4PH is lighter for a stiff rod or tie (tension), strong rod or tie.

Part that must beMagnesium AZ91DStainless Steel 17-4PH
Stiff rod or tie (tension)2% heavierlighter
Stiff beam (bending)lighter2.06x heavier
Stiff panel or platelighter2.63x heavier
Strong rod or tie1.97x heavierlighter
Strong beamlighter3% heavier
Strong panel or platelighter48% 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 Stainless Steel 17-4PH?

Magnesium AZ91D conducts heat better: 72 W/m·K against 17.9 W/m·K for Stainless Steel 17-4PH.

Which expands less with temperature?

Stainless Steel 17-4PH expands less: 10.8 µm/m·K against 25 µm/m·K for Magnesium AZ91D.

Among 72 materials

1k10k0.1110100Density (kg/m³)Young's modulus (GPa)Plastic PLAPlastic PETGPlastic ABSPlastic TPUPlastic NylonAluminumSteelIronTitaniumSteel AISI 1018Stainless Steel 304Stainless Steel 316Aluminum 6061-T6Aluminum 7075-T6Brass C360Copper C110GlassSteel AISI 1045Steel AISI 4340Steel A992Stainless Steel 303Aluminum 2024-T351Aluminum 5052-H32Aluminum 7050-T7451Titanium Ti-6Al-4VBrass C260Nickel Inconel 718Magnesium AZ31B-H24Zinc Zamak 3Plastic ABS (bulk/injection)Plastic PolycarbonatePlastic POM/AcetalPlastic Nylon PA6Plastic Nylon PA66Plastic PEEKPlastic UHMWPEPlastic HDPEPlastic PolypropylenePlastic PMMAFDM ASAFDM PolycarbonateFDM PAHT-CFFDM HIPSSLA Resin Tough 2000SLS PA12 NylonDMLS AlSi10Mg AluminumDMLS Ti-6Al-4V ELI TitaniumDMLS 316L Stainless SteelDMLS 17-4PH Stainless SteelPCB Laminate FR-4SiliconCeramic Alumina 96%Ceramic Aluminum NitrideAluminum A380Aluminum 6063-T6Aluminum 1100-OAluminum ADC12Solder SAC305Plastic PBT GF30Plastic PPS GF40Plastic LCP GF30Magnesium AZ91DStainless Steel 17-4PH
Stiffness against density
1k10k101001kDensity (kg/m³)Yield strength (MPa)Plastic PLAPlastic PETGPlastic ABSPlastic TPUPlastic NylonRubberAluminumSteelIronTitaniumSteel AISI 1018Stainless Steel 304Stainless Steel 316Aluminum 6061-T6Aluminum 7075-T6Brass C360Copper C110GlassSteel AISI 1045Steel AISI 4340Steel A992Stainless Steel 303Aluminum 2024-T351Aluminum 5052-H32Aluminum 7050-T7451Titanium Ti-6Al-4VBrass C260Nickel Inconel 718Magnesium AZ31B-H24Zinc Zamak 3Plastic ABS (bulk/injection)Plastic PolycarbonatePlastic POM/AcetalPlastic Nylon PA6Plastic Nylon PA66Plastic PEEKPlastic PTFEPlastic UHMWPEPlastic HDPEPlastic PolypropylenePlastic PMMAFDM ASAFDM PolycarbonateFDM PAHT-CFFDM HIPSSLA Resin Tough 2000SLA Resin Elastic 50ASLS PA12 NylonDMLS AlSi10Mg AluminumDMLS Ti-6Al-4V ELI TitaniumDMLS 316L Stainless SteelDMLS 17-4PH Stainless SteelBrickPCB Laminate FR-4SiliconCeramic Alumina 96%Aluminum A380Aluminum 6063-T6Aluminum 1100-OAluminum ADC12Solder SAC305Plastic PBT GF30Plastic PPS GF40Plastic LCP GF30Magnesium AZ91DStainless Steel 17-4PH
Strength against density

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