ZA27
Foundry Zinc alloy.
ZA27 conforms to BS EN 1774, which is suitable for casting manufacture using either sand or permanent mould casting techniques. This alloy is the strongest of the three ZA alloys developed by Noranda research in Canada its properties exceeding the traditional foundry materials in many instances.
Application
ZA 27 is a zinc alloy containing 27% aluminium. It has exceptionally high strength and excellent bearing properties. ZL 27 has a wide freezing range, which can raise casting difficulties if good casting techniques are not observed. It is advisable to ensure that even casting sections of 6 - 8 mm thickness are applied. However, where heavier localised sections are required it is essential that these are fed directly to prevent under side or excessive shrinkage. Visible or important faces of any part should upper most on the pattern or in the die. This alloy also has excellent machining characteristics, good corrosion resistance and will accept a variety of decorative and protective surface finishes.
It should be specified where high strength is important, as the alloy will compete with moderately high strength materials that cannot be cast using high-pressure diecasting. ZL 27 offers the extended tool life applicable to zinc alloys which, when combined with its higher strength and hardness makes the alloy an automatic choice when aluminium alloys are unable to meet the service conditions anticipated.
A Bearing Design Manual and design guideline for Gravity Casting of ZL 27 are is available free of charge, directly from Brock.
Advice should be sought from The Brock Metal Company before designing or specifying this alloy for any application. Castings manufactured from this alloy display quite marked changes in properties during ageing and these must be taken into account at the design stage.
| Alloy Designation | ZaAl27Cu2 | Colour code | White + violet. |
|---|---|---|---|
| Short designation | ZL 27 | Alloy Number. | ZL2720 |
| Chemical composition of Ingots. | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Al | Cu | Mg | Pb | Cd | Sn | Fe | Ni | Si | |
| Minimum | 2.25 | 2.0 | 0.012 | ||||||
| Maximum | 28.0 | 2.5 | 0.02 | 0.005 | 0.005 | 0.002 | 0.07 | -- | 0.07 |
| MECHANICAL PROPERTIES | ||
|---|---|---|
| Supplied in diecast form. | As Cast | Aged |
| Tensile strength | 424 MPa | 367 MPa |
| Yield strength | 371 MPa | 317 MPa |
| Impact strength | 40 Joules | 40 Joules |
| Elongation 50mm | 1.0% | 1.0 % |
| Shear strength | 296 MPa | 234 MPa |
| Compressive yield strength | 385 MPa | 288 MPa |
| Fatigue Strength | 145 MPa | -- |
| Hardness BHN 500Kg | 117 max | 111 max |
| PHYSICAL PROPERTIES | |
|---|---|
| Melting range | 376 - 484° C |
| Density | 5.0 g / cm3 |
| Coefficient of Thermal expansion | 26 um/m0 C |
| Thermal Conductivity | 125.5 W/m0 C |
| Electrical Conductivity | 28.3 % IACS |
| Electrical Resistivity | 5.8 u ohm-cm at 200 C |
