Aluminium Zinc Foundry Alloy ZA27
Mechanical Properties
|
|
Sand Cast |
Heat Treated |
|
Tensile Strength (N/mm2) |
400-440 |
310-324 |
|
Elongation (%) |
3-6 |
8-11 |
|
Brinell Hardness |
110-120 |
90-100 |
|
Impact Strength at 20°C (J) |
34-54 |
47-74 |
Strength at elevated temperatures
ZA27 can be considered for applications whose service temperatures are as high as 150°C. Reference should be made to the alloy's mechanical and physical properties at elevated temperatures. For continually stressed applications, reference should be made to ZA27 creep properties.
Physical Properties of ZA27 Coefficient of Thermal Expansion (per °C @ 20-100°C) 0.0000026 Thermal conductivity (cal/cm2/cm/°C @ 25°C) Electrical conductivity (% copper standard @ 20°C) 28 Density (g/cm3) 5 Freezing range (°C) approx. 490-380
Machinability of ZA27
This alloy has excellent machining characteristics which means fast, efficient machining and long tool life. It is ideal for components requiring substantial or difficult machining.
Corrosion Resistance
ZA27 has good corrosion resistance but weathering will turn the surface grey in colour, therefore, if required for decorative purposes, it is necessary to add a protective coating such as lacquer or paint. For more corrosive environments, zinc anodising should be considered.
Anodising
A process for anodising zinc and zinc alloy die castings has been developed and is reported to give excellent resistance to salt water and good resistance to abrasion. The finish is available only in matt light green, grey and brownish tints. The treatment is covered by U.S. Government specification MIL-A-81801.
Heat Treatment
Elongation properties can be further improved by simple heat treatment of the castings. This treatment consists of 3 hours at 320°C and furnace cooled.
Application and General notes
ZA27 has a whole range of potential stressed and functional applications. The high tensile properties of the alloy, coupled with its castability, enable the engineer to design in strength but at the same time reduce the overall material content of competitive materials. ZA27 has good bearing properties, and is very suitable for wear resistant applications.