ASTM_B_661_-_12.pdf

Designation:B66112Standard Practice forHeat Treatment of Magnesium Alloys1This standard is issued under the fixed designation B661;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1.Scope*1.1This practice is intended as an aid in establishing asuitable procedure for the heat treatment of magnesium alloysto assure proper physical and mechanical properties.1.2Times and temperatures are typical for various forms,sizes,and manufacturing methods and may not exactly de-scribe the optimum heat treatment for a specific item.Consequently,it is not intended that this practice be used as asubstitute for a detailed production process or procedure.1.3 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2B557 Test Methods for Tension Testing Wrought and CastAluminum-and Magnesium-Alloy ProductsE21 Test Methods for Elevated Temperature Tension Tests ofMetallic MaterialsE527 Practice for Numbering Metals and Alloys in theUnified Numbering System(UNS)3.Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 agingDescribes a time-temperature-dependentchange in the properties of certain alloys.Except for strainaging and age softening,it is the result of precipitation from asolid solution of one or more compounds whose solubilitydecreases with decreasing temperature.For each alloy suscep-tible to aging,there is a unique range of time-temperaturecombinations to which it will respond.3.1.2 heat treatmentAcombination of heating and coolingoperations applied to a metal or alloy in the solid state to obtaindesired conditions of properties.Heating for the sole purposeof hot working is excluded from the meaning of this definition.3.1.3 solution heat treatmentA treatment in which analloy is heated to a suitable temperature and held at thistemperature for a sufficient length of time to allow a desiredconstituent to enter into solid solution,followed by rapidcooling to hold the constituent in solution.The material is thenin a supersaturated,unstable state,and may subsequentlyexhibit Age Hardening.3.1.4 quenchingRapid cooling.When applicable,the fol-lowing more specific terms should be used:still air quenching,forced air quenching,hot water/polymer quenching.3.1.5 T4Solution heat-treated and naturally aged to asubstantially stable condition.3.1.6 T5Artificially aged only:Applied to products whichare artificially aged after an elevated-temperature rapid-coolfabrication process,such as casting or extrusion,to improvemechanical properties or dimensional stability,or both.3.1.7 T6Solution heat-treated and then artificially aged:Applies to products which are not cold worked after solutionheat-treatment.4.Apparatus4.1 Furnaces used for the heat treatment of magnesium areusually of the air chamber type and may be electrically heatedor oil-or gas-fired.Because of the atmospheres used forsolution heat treatment,furnaces must be gas tight and containsuitable equipment for the introduction of protectiveatmospheres,and means for control of those atmospheres.Inorder to promote uniformity of temperature,furnaces should beequipped with a high-velocity fan or comparable means forcirculating the atmosphere.In the design of the furnace it isdesirable that there be no direct radiation from the heatingelements or impingement of the flame on the magnesium.4.2 Automatic recording and control equipment to controlthe temperature of the furnaces,which must be capable of1This practice is under the jurisdiction of ASTM Committee B07 on LightMetals and Alloys and is the direct responsibility of Subcommittee B07.04 onMagnesium Alloy Cast and Wrought Products.Current edition approved Sept.1,2012.Published October 2012.Originallyapproved in 1979.Last previous edition approved in 2006 as B661 06.DOI:10.1520/B0661-12.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.*A Summary of Changes section appears at the end of this standardCopyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 maintaining temperature in the working zone to within 610F(66C)of the specified temperature.4.3There must be a separate manual reset safety cutoutwhich will turn off the heat source in the event of anymalfunctioning or failure of the regular control equipment.Thes