Aluminium / Aluminum 7178 Alloy (UNS A97178)

Topics Covered

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

Introduction

Aluminium / Aluminum alloys are good low-temperature alloys that gain strength when exposed to subzero temperatures. These alloys lose their strength when exposed to high temperatures. Aluminium / Aluminum alloys are sensitive to high temperatures ranging between 200 and 250°C (392 and 482°F). They have strong corrosion resistance characteristics and high electrical conductivity.

The following datasheet provides an overview of Aluminium / Aluminum 7178 alloy.

Chemical Composition

The chemical composition of Aluminium / Aluminum 7178 alloy is outlined in the following table.

Element Content (%)
Aluminium / Aluminum, Al 88.1
Zinc, Zn 6.8
Magnesium, Mg 2.7
Copper, Cu 2.0
Chromium, Cr 0.26

Physical Properties

The following table shows the physical properties of Aluminium / Aluminum 7178 alloy.

Properties Metric Imperial
Density 2.82 g/cm3 0.1018 lb/in3
Melting point 482°C 900°F

Mechanical Properties

The mechanical properties of Aluminium / Aluminum 7178 alloy are displayed in the following table.

Properties Metric Imperial
Elastic modulus 70-80 GPa 10152-11603 ksi
Poisson's ratio 0.33 0.33

Thermal Properties

The thermal properties of Aluminium / Aluminum 7178 alloy are given in the following table.

Properties Conditions
T (ºC) Treatment
Thermal expansion 23.4 (10-6/ºC) 20-100 -

Other Designations

Equivalent materials to Aluminium / Aluminum 7178 alloy are:

  • ASTM B209
  • ASTM B221
  • ASTM B241
  • ASTM B316
  • QQ A-200/13
  • QQ A-200/14
  • QQ A-250/14
  • QQ A-250/21
  • QQ A-250/28
  • QQ A-430
  • SAE J454

Fabrication and Heat Treatment

Annealing

Aluminium / Aluminum 7178 alloy is annealed for 3 hours at 413°C (775°F), cooled to 204°C (400°F) or even less, heated to 232°C (450°F), held for 4 hours and finally cooled in air. This process produces O temper and removes the solution heat treatment condition.

Cold Working

Aluminium / Aluminum 7178 alloy is difficult to be cold worked.

Welding

Aluminium / Aluminum 7178 alloy can be welded by resistance welding methods.

Forming

Aluminium / Aluminum 7178 alloy is difficult to form, or work, in any of the T tempers.

Machinability

Aluminium / Aluminum 7178 alloy has good machinability, especially in the annealed state. Usage of oil lubricants is recommended for this process.

Heat Treatment

Aluminium / Aluminum 7178 alloy can be heat treated at 468°C (875°F) and then water quenched.

Hardening

The Aluminium / Aluminum 7178 alloy has precipitation hardening characteristic.

Applications

Aluminium / Aluminum 7178 alloy is used in structures such as aircrafts.

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