1、Designation: B 661 06Standard Practice forHeat Treatment of Magnesium Alloys1This standard is issued under the fixed designation B 661; 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 parenthe
2、ses indicates the year of last reapproval. Asuperscript epsilon (e) 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*1.1 This practice is intended as an aid in establishing asuitable procedur
3、e for the heat treatment of magnesium alloysto assure proper physical and mechanical properties.1.2 Times 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. Conse-quently, it is not intended th
4、at 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
5、and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2B 557 Test Methods of Tension Testing Wrought and CastAluminum- and Magnesium-Alloy ProductsE21 Test Methods for Elevated Temperature Tension Testsof Metallic MaterialsE 527 Practice fo
6、r Numbering Metals and Alloys (UNS)3. Terminology3.1 Definitions of Terms Specific to This Standard3.1.1 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 m
7、ore 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
8、 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
9、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 b
10、e 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
11、 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 areu
12、sually 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 protective atmo-spheres, and means for control of those atmospheres. In orde
13、rto 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 Automa
14、tic recording and control equipment to controlthe temperature of the furnaces, which must be capable ofmaintaining temperature in the working zone to within 610F(66C) of the specified temperature.4.3 There must be a separate manual reset safety cutoutwhich will turn off the heat source in the event
15、of anymalfunctioning or failure of the regular control equipment.These safety cutouts shall be set as closely as practicable abovethe maximum temperature for the alloy being heat treated. This1This practice is under the jurisdiction of ASTM Committee B07 on LightMetals and Alloys and is the direct r
16、esponsibility of Subcommittee B07.04 onMagnesium Alloy Cast and Wrought Products.Current edition approved March 1, 2006. Published March 2006. Originallyapproved in 1979. Last previous edition approved in 2003 as B 661 03.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontac
17、t ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West C
18、onshohocken, PA 19428-2959, United States.will be above the variation expected, but shall not be more than10F (6C) above the maximum solution heat treating tempera-ture for the alloy being heat treated. Protective devices shallalso be installed to turn off the heat source in case of stoppageof circu
19、lation of air, and they shall be interconnected with amanual reset control.4.4 The furnaces or ovens used for aging treatments may beheated by means of electricity, gas, or oil. The temperature atany point in the working zone, for any charge, shall bemaintained within 610F (66C) of the desired aging
20、 tem-perature after the furnace has been brought up to the agingtemperature.4.5 Quenching:4.5.1 Normally magnesium work loads are cooled in air.This should be by fan cooling the furnace charge after removalfrom the furnace in such a way that the cooling is uniform onvarious parts of the furnace char
21、ge.4.5.2 Some alloys (notably EV31A, EQ21A, and QE22A)are quenched in water or other suitable media from the solutionheat treating temperature. Quench facilities should be situatednear the heat treatment furnaces. If required, means of heatingthe quench medium should be provided. Handling equipments
22、hall be such that it is possible to quench heat treatment loadswithin 30 s after the opening of the furnace door.5. Calibration and Standardization5.1 Calibration of Equipment:5.1.1 Surveys:5.1.1.1 Perform a temperature survey, to ensure compliancewith the applicable recommendations presented herein
23、 for eachfurnace.5.1.1.2 Make a new temperature survey after any changesin the furnace that may affect operational characteristics.5.1.2 Furnace Calibration:5.1.2.1 Make the initial temperature survey at the maxi-mum and minimum temperature of solution heat treatmentsand aging heat treatment for whi
24、ch each furnace is to be used.There shall be at least one test location for each 25 ft3(0.7 m3)of air furnace volume up to a maximum of 40 test locationswith a minimum of nine test locations.5.1.2.2 After the initial survey, survey each furnacemonthly, except as provided in 5.1.2.7. The monthly surv
25、eyshall be at one operating temperature for solution heat treat-ment and one for aging heat treatment.5.1.2.3 For the monthly surveys there shall be at least onetest location for each 40 ft3(1.13 m3) load volume.5.1.2.4 For furnaces of 10 ft3(0.28 m3) or less thetemperature survey may be made with a
26、 minimum of threethermocouples located at front, center, and rear, or at top,center, and bottom of the furnace.5.1.2.5 Perform the surveys in such manner as to reflect thenormal operating characteristics of the furnace. If the furnace isnormally charged after being stabilized at the correct operatin
27、gtemperature, similarly charge the temperature-sensing ele-ments. If the furnace is normally charged cold, charge thetemperature-sensing elements cold. After insertion of thetemperature-sensing elements, readings should be taken fre-quently enough to determine when the temperature of thehottest regi
28、on of the furnace approaches the bottom of thetemperature range being surveyed. From that time until thermalequilibrium is reached, the temperature of all test locationsshould be determined at 2-min intervals in order to detect anyovershooting. After thermal equilibrium is reached, readingsshould be
29、 taken at 5-min intervals for sufficient time todetermine the recurrent temperature pattern, but for not lessthan 30 min. Before thermal equilibrium is reached, none of thetemperature readings should exceed the maximum temperatureof the range being surveyed. After thermal equilibrium isreached, the
30、maximum temperature variation of all elements(both load and furnace thermocouples) shall not exceed 20F(11C) and shall not vary outside the range being surveyed.5.1.2.6 For furnaces used only for treatments other thansolution heat treatment, after the initial temperature uniformitysurvey as outlined
31、 in 5.1.2.5, surveys need not be made moreoften than at each 6-month interval, provided that (a) testspecimens from each lot are tested and meet applicablematerial specifications requirements, (b) the furnace isequipped with a multipoint recorder, or (c) one or moreseparate load thermocouples are em
32、ployed to measure andrecord actual metal temperatures.5.1.2.7 Monthly surveys for batch furnaces are not neces-sary when the furnace is equipped with a permanent multipointrecording system with at least two sensing thermocouples ineach working zone, or when one or more separate loadthermocouples are
33、 employed to measure actual metal tempera-ture, providing that uniformity surveys show a history ofsatisfactory performance for a period of at least 6 months. Thesensing thermocouples shall be installed so as to record thetemperature of the heated air or actual metal temperatures.However, periodic s
34、urveys shall also be made at 6-monthintervals in accordance with the procedures outlined for themonthly survey.5.1.2.8 Do not use furnace control temperature-measuringinstruments to read the temperature of the test temperature-sensing elements.5.1.3 Temperature-Measuring System CheckCheck theaccurac
35、y of temperature-measuring system under operatingconditions weekly. Check should be made by inserting acalibrated test temperature-sensing element adjacent to thefurnace temperature-sensing element and reading the testtemperature-sensing element with a calibrated test potentiom-eter. When the furnac
36、e is equipped with dual potentiometermeasuring systems, which are checked daily against eachother, the above checks may be conducted every three monthsrather than every week. Calibrate the test temperature-sensingelement, potentiometer, and cold junction compensation com-bination against National In
37、stitute of Standards and Technol-ogy primary or secondary certified temperature-sensing ele-ments, within the previous three months, to an accuracy of62F (1.1C).5.1.4 RecordsMaintain records for each furnace for atleast 7 years to show compliance with this standard. Theserecords shall include the fo
38、llowing: furnace number or descrip-tion; size; temperature range of usage; whether used forsolution heat treatment or aging heat treatment, or both;temperature(s) at which uniformity was surveyed; dates of eachB661062survey; number and locations of thermocouples used; and datesof major repairs or al
39、terations.5.2 Test and Verification of Equipment:5.2.1 Test Requirements:5.2.1.1 Heat-Treating Equipment, operated in accordancewith documented procedures, shall have a demonstrated capa-bility of producing material and components meeting themechanical and physical properties specified for each heat
40、treated alloy.5.2.1.2 Use of Production Test ResultsIn all cases, theresults of tests made to determine conformance of heat-treatedmaterial to the requirements of the respective material speci-fications are acceptable as evidence of the properties beingobtained with the equipment and procedure empl
41、oyed.5.2.2 Mechanical PropertiesThe heat treated (or reheattreated) test specimen shall have tensile strength, yieldstrength, and elongation properties not less than those specifiedin the applicable material specification or detail drawings. Therequired tests for alloys shall be in accordance with t
42、herequirements of the respective specifications and shall conformto Methods B 557 or Test Methods E21, or both.5.2.2.1 Microscopical ExaminationThe tensile test maybe supplemented by a microscopical examination of the testbars or selected castings at the discretion of the procuringactivity. Take a s
43、ingle representative sample for each of thespecified tests if the furnace selected for routine inspectioncontains a load that is homogeneous as to alloy, form, and sizeof part. Select two specimens to represent the least massive andthe most massive portions of the charge. In the event ofnonhomogenei
44、ty as to alloy and when the recommended heattreatments for the respective alloys differ, prepare additionalsamples.5.2.2.2 Eutectic Melting and High Temperature Oxidationof CastingsSection, mount, and prepare specimens from theheat treated samples for microscopical examination. Examinethe unetched s
45、urface at a 500-diameter magnification with ametallurgical microscope. The presence of eutectic melting orhigh temperature oxidation shall be considered evidence ofimproper heat treatment.5.3 Interpretation of Results:5.3.1 Test specimens prepared in accordance with 5.2.1 andtreated in accordance wi
46、th the applicable parts of Section 6shall meet the requirements specified below. Failure to meetthe specified mechanical or physical requirements is reason todisqualify the heat-treating equipment and associated processuntil the reason for the failure is determined and appropriatecorrective action c
47、ompleted.5.3.2 Status of AlloysAlloys heat treated in the furnacesince the time of the previous satisfactory tests and foundunsatisfactory shall be rejected or reheat treated (beginningwith the solution heat treatment where applicable) in anacceptable furnace, depending on the character of the faile
48、dtests. Alloys in which eutectic melting, and high temperatureoxidation is found shall be rejected and no reheat treatmentpermitted. Alloys that fail for reasons other than those enumer-ated above may be reheat treated.5.3.3 Test ReportsTest reports shall be identified as to theequipment used and he
49、at-treat lots of material associated withthe tests and shall be retained and readily retrievable for anappropriate period.6. Procedure and Operations6.1 Sand and Mold Castings:6.1.1 Heat TreatmentHeat treat castings at temperaturesnot exceeding the maximum temperatures specified in Table 1.Suggested heat treating temperature ranges are shown in Table1.6.1.1.1 The furnace should be loaded in such a manner as topermit adequate circulation of the furnace atmosphere. Giveattention to providing necessary support to castings susceptibleto warpage.6.1.2 Hold the cha
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