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PRODUCT DATA of AA7178-T76
MaterialAA7178-T76
General InformationAlloy 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 CompositionAl-0.25Cr-2.2Cu-2.7Mg-7Zn
EXPERIENCE IN PRACTICE
Development StatusCommercial Product
Equivalent DesignationsAA 7178
PHYSICAL PROPERTIES
Crystal StructureFace centered cubic (fcc)
Specific Gravity2.83
Magnetic PropertiesNonmagnetic
ELASTIC PROPERTIES
Tensile Modulus71.7 GPa
Poisson Ratio0.33
THERMAL PROPERTIES
Thermal Conductivity125 W/m.K
Thermal Expansion Coefficient23.4 μstrain/°C
Melting Range477 to 629 °C
Specific Heat0.856 J/g.K
RELEVANT PROPERTIES FOR USE IN SPACE COMMUNITY
General Corrosion StatusRequires specific corrosion protection
Stress Corrosion StatusModerate Resistance to SCC: Table 2
Remark: Requires Stress corrosion evaluation form
Data Quality: Design Data
EMF vs SCE-0.74 V
Bimetallic CorrosionCan 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
MachinabilityMachinability of this alloy is good, especially in the annealed condition. Use of oil lubrication during machining is recommended.
AgingPrecipitation heat treatment (Aging) is done at 121 CF for 24 hours to obtain T6 and T651 tempers.
Atomic OxygenNo effect
SPECIAL RECOMMENDATIONS
Lessons LearnedIn some cases, this alloy responds poorly to black anodising.