Magnesium AZ31B Alloy (UNS M11311)

Topics Covered

Introduction
Chemical Composition
Physical Properties
Mechanical Properties
Thermal Properties
Other Designations
Fabrication and Heat Treatment
     Machinability
     Forming
     Welding
     Annealing
Applications

Introduction

Magnesium alloys are light weight and have high machinability. They are often anodized to improve their corrosion resistance. They are designated using the ASTM and SAE system in which the first part indicates the two main alloying elements in the alloy and the second part represents their percentages.

Magnesium AZ31B alloy is available in different forms such as plate, sheet, and bar. It is an alternative to aluminum alloys as it has high strength to weight ratio. It is widely available when compared to other magnesium grades. The following datasheet gives an overview of magnesium AZ31B alloy.

Chemical Composition

The following table shows the chemical composition of magnesium AZ31B alloy.

Element Content (%)
Magnesium, Mg 97
Aluminum, Al 2.50 - 3.50
Zinc, Zn 0.60 - 1.40
Manganese, Mn  0.20
Silicon, Si 0.10
Copper, Cu 0.050
Calcium, Ca 0.040
Iron, Fe 0.0050
Nickel, Ni 0.0050

Physical Properties

The physical properties of extruded magnesium AZ31B alloy are given in the following table.

Properties Metric Imperial
Density 1.77 g/cm3 0.0639 lb/in³

Mechanical Properties

The mechanical properties of magnesium AZ31B alloy are outlined in the following table.

Properties Metric Imperial
Tensile strength 260 MPa 37700 psi
Yield strength (strain 0.200%) 200 MPa 29000 psi
Compressive yield strength (at 0.2% offset) 97 MPa 14100 psi
Ultimate bearing strength 385 MPa 55800 psi
Bearing yield strength 230 MPa 33400 psi
Shear strength 130 MPa 18900 psi
Shear modulus 17 GPa 2470 ksi
Elastic modulus 44.8 GPa 6498 ksi
Poisson's ratio 0.35 0.35
Elongation at break (in 50 mm) 15% 15%
Hardness, Brinell (500 kg load, 10 mm ball) 49 49
Charpy impact (V-notch) 4.30 J 3.17 ft-lb

Thermal Properties

The thermal properties of magnesium AZ31B alloy are highlighted in the following table.

Properties Metric Imperial
Thermal expansion co-efficient (0-100°C/32-212°F) 26 µm/m°C 14.4 µin/in°F
Thermal conductivity 96 W/mK 666 BTU in/hr.ft².°F

Other Designations

Other designations that are equivalent to magnesium AZ31B alloy include:

  • ASTM B107
  • ASTM B90
  • ASTM B91

Fabrication and Heat Treatment

Machinability

Magnesium AZ31B alloy has good machinability. It is flammable, so extreme care should be taken while performing this process. A lubricant is used to perform machining process. The machinist is required to constantly monitor the operation with a magnesium fire arresting kit.

Forming

Magnesium AZ31B alloy can be formed by preheating at 260°C (500°F).

Welding

Magnesium AZ31B alloy can be welded using metal arc and gas tungsten arc welding techniques.

Annealing

Magnesium AZ31B alloy is stress relieved at 149°C (300°F) for 30 to 60 minutes followed by cooling in air. Full annealing can be done at 344°C (650°F) followed by slowly cooling in the furnace.

Applications

Magnesium AZ31B alloy is mainly used in aerospace applications and general commercial applications.

Comments

  1. Pankaj SHARMA Pankaj SHARMA India says:

    What is the meaning of B in AZ31B

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