Gravity Casting Alloys

Overview

ZA alloys were initially developed for gravity casting. Their mechanical properties compete directly with bronze, cast iron and aluminum using sand, permanent mold and plaster mold casting methods. Beginning in the late 1950's and continuing into the 1970's, Noranda, New Jersey Zinc Co. Ltd., St. Joe Mineral Co. and ILZRO contributed to development of the ZA alloy group. Zinc and Aluminum are the major alloy constituents, along with other minor additions of magnesium and copper. The numbers associated with the name represent the amount of aluminum in the alloy (i.e. ZA8 has 8% aluminum). Distinguishing features of ZA alloys include high as-cast strength, excellent bearing properties, as well as low energy (melting) requirements..

Eastern Alloys manufactures the entire ZA alloy group. There are many different gravity-casting processes such as permanent mold, graphite permanent mold, plaster, and sand. In general these processes are used for low to medium volume requirements, and also as a prototyping technique.

Mechanical Properties

	ZA-8		ZA-12		ZA-27
	Sand Cast	Perm Mold	Sand Cast	Perm Mold	Sand Cast	Sand Cast HT
Ultimate Tensile Strength: psi x 103 (MPa)	38 (263)	32-37 (221-255)	40-46 (276-317)	45-50 (310-345)	58-64 (400-441)	45-47 (310-324)
Yield Strength - 0.2% Offset: psi x 103 (MPa)	29 (200)	30 (206)	31 (214)	39 (269)	54 (372)	37 (255)
Elongation: % in 2"	1-2	1-2	1-3	1-3	3-6	8-11
Shear Strength: psi x 103 (MPa)	-	35 (241)	37 (255)	-	42 (290)	33 (228)
Hardness: Brinell	85	85-90	89-105	89-105	110-120	90-110
Impact Strength: ft-lb (J)	156 (20)	-	193 (25)	-	353 (47)	433 (58)
Fatigue Strength Rotary Bend - 5x108 cycles: psi x 103 (MPa)	-	7.5 (52)	15 (103)	-	25 (172)	15 (103)
Compressive Yield Strength 0.1% Offset: psi x 103 (MPa)	29 (199)	31 (214)	33(227)	34 (234)	48 (331)	37 (255)
Modulus of Elasticity - psi x 106 (MPa x 103)	12.4 (85.5)	12.47 (85.5)	12.07 (82.7)	12.07 (82.7)	11.37 (77.9)	11.37 (77.9)
Poisson's Ratio	0.29	0.29	0.30	0.30	0.32	0.32

Physical Properties

	ZA-8		ZA-12		ZA-27
	Sand Cast	Perm Mold	Sand Cast	Perm Mold	Sand Cast	Sand Cast HT
Density: lb/cu in (g/cm3)	0.227 (6.3)	0.227 (6.3)	0.218 (6.0)	0.218 (6.0)	0.181 (5.0)	0.181 (5.0)
Melting Range: °F (°C)	707-759 (375-404)	707-759 (375-404)	710-810 (377-432)	710-810 (377-432)	708-903 (376-484)	708-903 (376-484)
Electrical Conductivity: %IACS	27.7	27.7	28.3	28.3	29.7	29.7
Thermal Conductivity: BTU/ft/hr/°F (W/m/hr/°C)	66.3 (114.7)	66.3 (114.7)	67.1 (116.1)	67.1 (116.1)	72.5 (125.5)	72.5 (125.5)
Coefficient of Thermal Expansion: 68-212°F µin/in/°F (100-200°C µm/mm/°C)	12.9 (23.3)	12.9 (23.3)	13.4 (24.2)	13.4 (24.2)	14.4 (26.0)	14.4 (26.0)
Specific Heat: BTU/lb/°F (J/kg/°C)	.104 (435)	.104 (435)	.107 (448)	.107 (448)	.125 (534)	.125 (534)
Pattern of Die Shrinkage: in/in	1/8 in/ft	5/32 in/ft	1/8 in/ft	5/32 in/ft	5/32 in/ft	5/32 in/ft

Compositions

Chemical Specification (per ASTM) (% by Weight)
	ZA-8		ZA-12		ZA-27
	Ingot	Casting	Ingot	Casting	Ingot	Casting
Al	8.2-8.8	8.0-8.8	10.8-11.5	10.5-11.5	25.5-28.0	25.0-28.0
Mg	.020-.030	.015-.030	.020-.030	.015-.030	.012-.020	.010-.020
Cu	0.8-1.3	.8-1.3	0.5-1.2	0.5-1.2	2.0-2.5	2.0- 2.5
Fe (max)	.065	.075	.065	.075	.072	.075
Pb (max)	.005	.006	.005	.006	.005	.006
Cd (max)	.005	.006	.005	.006	.005	.006
Sn (max)	.002	.003	.002	.003	.002	.003
Ni (other)x10	-	-	-	-	-	-
Zn	Bal.	Bal.	Bal.	Bal.	Bal.	Bal.
Color Code ASTM B908	Blue		Orange		Purple
Color Code ASTM B908

Shapes and Sizes

Products Shapes and Weights (lbs.) (click on a shape below for details)
	Standard Ingots	Standard Sow
ZA-8	22	2,200
ZA-12	21	-
ZA-27	17	-