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	PRODUCT DATA of AA7178-T76

Material	AA7178-T76
General Information	Alloy 7178 is a high strength alloy with magnesium and copper as the major alloying elements. It is heat treatable and develops improved mechanical properties from precipitation hardening.
Chemical Composition	Al-0.25Cr-2.2Cu-2.7Mg-7Zn

	EXPERIENCE IN PRACTICE

Development Status	Commercial Product
Equivalent Designations	AA 7178

	PHYSICAL PROPERTIES

Crystal Structure	Face centered cubic (fcc)
Specific Gravity	2.83
Magnetic Properties	Nonmagnetic

	ELASTIC PROPERTIES

Tensile Modulus	71.7 GPa
Poisson Ratio	0.33

	THERMAL PROPERTIES

Thermal Conductivity	125 W/m.K
Thermal Expansion Coefficient	23.4 μstrain/°C
Melting Range	477 to 629 °C
Specific Heat	0.856 J/g.K

	RELEVANT PROPERTIES FOR USE IN SPACE COMMUNITY

General Corrosion Status	Requires specific corrosion protection
Stress Corrosion Status	Moderate Resistance to SCC: Table 2 Remark: Requires Stress corrosion evaluation form Data Quality: Design Data
EMF vs SCE	-0.74 V
Bimetallic Corrosion	Can be used in a non-controlled environment: Al alloys, Cd Can be used in a clean room environment: Mg, Sn-Pb alloys (all), Sn, Pb, Zn, Be Needs specific measures: All others Test:ECSS-Q-ST-70C Rev.1 Table 5.1 Data Quality: Design Data
Machinability	Machinability of this alloy is good, especially in the annealed condition. Use of oil lubrication during machining is recommended.
Aging	Precipitation heat treatment (Aging) is done at 121 CF for 24 hours to obtain T6 and T651 tempers.
Atomic Oxygen	No effect

	SPECIAL RECOMMENDATIONS

Lessons Learned

In some cases, this alloy responds poorly to black anodising.