1、Designation: B661 06 B661 12Standard 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 pa
2、rentheses 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*1.1 This practice is intended as an aid in establishing a suitable pr
3、ocedure for the heat treatment of magnesium alloys to assureproper physical and mechanical properties.1.2 Times and temperatures are typical for various forms, sizes, and manufacturing methods and may not exactly describe theoptimum heat treatment for a specific item. Consequently, it is not intende
4、d that this practice be used as a substitute for a detailedproduction process or procedure.1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practi
5、ces and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2B557 Test Methods for Tension Testing Wrought and Cast Aluminum- and Magnesium-Alloy ProductsE21 Test Methods for Elevated Temperature Tension Tests of Metallic MaterialsE527 Practice
6、 for Numbering Metals and Alloys in the Unified Numbering System (UNS)3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 agingDescribes a time-temperature-dependent change in the properties of certain alloys. Except for strain aging and agesoftening, it is the result of precipita
7、tion from a solid solution of one or more compounds whose solubility decreases withdecreasing temperature. For each alloy susceptible to aging, there is a unique range of time-temperature combinations to whichit will respond.3.1.2 heat treatmentA combination of heating and cooling operations applied
8、 to a metal or alloy in the solid state to obtaindesired conditions of properties. Heating for the sole purpose of hot working is excluded from the meaning of this definition.3.1.3 solution heat treatmentA treatment in which an alloy is heated to a suitable temperature and held at this temperature f
9、ora sufficient length of time to allow a desired constituent to enter into solid solution, followed by rapid cooling to hold theconstituent in solution. The material is then in a supersaturated, unstable state, and may subsequently exhibit Age Hardening.3.1.4 quenchingRapid cooling. When applicable,
10、 the following more specific terms should be used: still air quenching, forcedair quenching, hot water/polymer quenching.3.1.5 T4Solution heat-treated and naturally aged to a substantially stable condition.3.1.6 T5Artificially aged only: Applied to products which are artificially aged after an eleva
11、ted-temperature rapid-coolfabrication process, such as casting or extrusion, to improve mechanical 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.1 This practice is unde
12、r the jurisdiction of ASTM Committee B07 on Light Metals and Alloys and is the direct responsibility of Subcommittee B07.04 on Magnesium AlloyCast and Wrought Products.Current edition approved March 1, 2006Sept. 1, 2012. Published March 2006October 2012. Originally approved in 1979. Last previous ed
13、ition approved in 20032006 asB661 03.B661 06. DOI: 10.1520/B0661-06.10.1520/B0661-12.2 For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summar
14、y page on the ASTM website.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends t
15、hat users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West
16、 Conshohocken, PA 19428-2959. United States14. Apparatus4.1 Furnaces used for the heat treatment of magnesium are usually of the air chamber type and may be electrically heated oroil- or gas-fired. Because of the atmospheres used for solution heat treatment, furnaces must be gas tight and contain su
17、itableequipment for the introduction of protective atmospheres, and means for control of those atmospheres. In order to promoteuniformity of temperature, furnaces should be equipped with a high-velocity fan or comparable means for circulating theatmosphere. In the design of the furnace it is desirab
18、le that there be no direct radiation from the heating elements or impingementof the flame on the magnesium.4.2 Automatic recording and control equipment to control the temperature of the furnaces, which must be capable ofmaintaining temperature in the working zone to within 610F (66C) of the specifi
19、ed temperature.4.3 There must be a separate manual reset safety cutout which will turn off the heat source in the event of any malfunctioningor failure of the regular control equipment. These safety cutouts shall be set as closely as practicable above the maximumtemperature for the alloy being heat
20、treated. This will be above the variation expected, but shall not be more than 10F (6C) abovethe maximum solution heat treating temperature for the alloy being heat treated. Protective devices shall also be installed to turnoff the heat source in case of stoppage of circulation of air, and they shal
21、l be interconnected with a manual reset control.4.4 The furnaces or ovens used for aging treatments may be heated by means of electricity, gas, or oil. The temperature at anypoint in the working zone, for any charge, shall be maintained within 610F (66C) of the desired aging temperature after thefur
22、nace has been brought up to the aging temperature.4.5 Quenching:4.5.1 Normally magnesium work loads are cooled in air. This should be by fan cooling the furnace charge after removal fromthe furnace in such a way that the cooling is uniform on various parts of the furnace charge.4.5.2 Some alloys (no
23、tably EV31A, EQ21A, and QE22A) are quenched in water or other suitable media from the solution heattreating temperature. Quench facilities should be situated near the heat treatment furnaces. If required, means of heating the quenchmedium should be provided. Handling equipment shall be such that it
24、is possible to quench heat treatment loads within 30 s afterthe 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 compliance with the applicable recommendations presented herein for eachfurnace.5.1
25、.1.2 Make a new temperature survey after any changes in the furnace that may affect operational characteristics.5.1.2 Furnace Calibration:5.1.2.1 Make the initial temperature survey at the maximum and minimum temperature of solution heat treatments and agingheat treatment for which each furnace is t
26、o be used. There shall be at least one test location for each 25 ft3 (0.7 m3) of air furnacevolume up to a maximum of 40 test locations with a minimum of nine test locations.5.1.2.2 After the initial survey, survey each furnace monthly, except as provided in 5.1.2.7. The monthly survey shall be at o
27、neoperating temperature for solution heat treatment and one for aging heat treatment.5.1.2.3 For the monthly surveys there shall be at least one test location for each 40 ft3 (1.13 m3) load volume.5.1.2.4 For furnaces of 10 ft3 (0.28 m3) or less the temperature survey may be made with a minimum of t
28、hree thermocoupleslocated 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 the normal operating characteristics of the furnace. If the furnace isnormally charged after being stabilized at the correct operating temperatu
29、re, similarly charge the temperature-sensing elements. Ifthe furnace is normally charged cold, charge the temperature-sensing elements cold. After insertion of the temperature-sensingelements, readings should be taken frequently enough to determine when the temperature of the hottest region of the f
30、urnaceapproaches the bottom of the temperature range being surveyed. From that time until thermal equilibrium is reached, thetemperature of all test locations should be determined at 2-min intervals in order to detect any overshooting. After thermalequilibrium is reached, readings should be taken at
31、 5-min intervals for sufficient time to determine the recurrent temperaturepattern, but for not less than 30 min. Before thermal equilibrium is reached, none of the temperature readings should exceed themaximum temperature of the range being surveyed. After thermal equilibrium is reached, the maximu
32、m temperature variation ofall elements (both load and furnace thermocouples) shall not exceed 20F (11C) and shall not vary outside the range beingsurveyed.5.1.2.6 For furnaces used only for treatments other than solution heat treatment, after the initial temperature uniformity surveyas outlined in 5
33、.1.2.5, surveys need not be made more often than at each 6-month interval, provided that (a) test specimens fromeach lot are tested and meet applicable material specifications requirements, (b) the furnace is equipped with a multipoint recorder,or (c) one or more separate load thermocouples are empl
34、oyed to measure and record actual metal temperatures.5.1.2.7 Monthly surveys for batch furnaces are not necessary when the furnace is equipped with a permanent multipointrecording system with at least two sensing thermocouples in each working zone, or when one or more separate load thermocouplesB661
35、 122are employed to measure actual metal temperature, providing that uniformity surveys show a history of satisfactory performancefor a period of at least 6 months. The sensing thermocouples shall be installed so as to record the temperature of the heated airor actual metal temperatures. However, pe
36、riodic surveys shall also be made at 6-month intervals in accordance with the proceduresoutlined for the monthly survey.5.1.2.8 Do not use furnace control temperature-measuring instruments to read the temperature of the test temperature-sensingelements.5.1.3 Temperature-Measuring System CheckCheck t
37、he accuracy of temperature-measuring system under operating conditionsweekly. Check should be made by inserting a calibrated test temperature-sensing element adjacent to the furnace temperature-sensing element and reading the test temperature-sensing element with a calibrated test potentiometer. Whe
38、n the furnace isequipped with dual potentiometer measuring systems, which are checked daily against each other, the above checks may beconducted every three months rather than every week. Calibrate the test temperature-sensing element, potentiometer, and coldjunction compensation combination against
39、 National Institute of Standards and Technology primary or secondary certifiedtemperature-sensing elements, within the previous three months, to an accuracy of 62F (1.1C).5.1.4 RecordsMaintain records for each furnace for at least 7 years to show compliance with this standard. These records shallinc
40、lude the following: furnace number or description; size; temperature range of usage; whether used for solution heat treatmentor aging heat treatment, or both; temperature(s) at which uniformity was surveyed; dates of each survey; number and locations ofthermocouples used; and dates of major repairs
41、or alterations.5.2 Test and Verification of Equipment:5.2.1 Test Requirements:5.2.1.1 Heat-Treating Equipment, operated in accordance with documented procedures, shall have a demonstrated capability ofproducing material and components meeting the mechanical and physical properties specified for each
42、 heat-treated alloy.5.2.1.2 Use of Production Test ResultsIn all cases, the results of tests made to determine conformance of heat-treated materialto the requirements of the respective material specifications are acceptable as evidence of the properties being obtained with theequipment and procedure
43、 employed.5.2.2 Mechanical PropertiesThe heat treated (or reheat treated) test specimen shall have tensile strength, yield strength, andelongation properties not less than those specified in the applicable material specification or detail drawings. The required tests foralloys shall be in accordance
44、 with the requirements of the respective specifications and shall conform to Methods B557 or TestMethods E21, or both.5.2.2.1 Microscopical ExaminationThe tensile test may be supplemented by a microscopical examination of the test bars orselected castings at the discretion of the procuring activity.
45、 Take a single representative sample for each of the specified tests ifthe furnace selected for routine inspection contains a load that is homogeneous as to alloy, form, and size of part. Select twospecimens to represent the least massive and the most massive portions of the charge. In the event of
46、nonhomogeneity as to alloyand when the recommended heat treatments for the respective alloys differ, prepare additional samples.5.2.2.2 Eutectic Melting and High Temperature Oxidation of CastingsSection, mount, and prepare specimens from the heattreated samples for microscopical examination. Examine
47、 the unetched surface at a 500-diameter magnification with a metallurgicalmicroscope. The presence of eutectic melting or high temperature oxidation shall be considered evidence of improper heattreatment.5.3 Interpretation of Results:5.3.1 Test specimens prepared in accordance with 5.2.1 and treated
48、 in accordance with the applicable parts of Section 6 shallmeet the requirements specified below. Failure to meet the specified mechanical or physical requirements is reason to disqualifythe heat-treating equipment and associated process until the reason for the failure is determined and appropriate
49、 corrective actioncompleted.5.3.2 Status of AlloysAlloys heat treated in the furnace since the time of the previous satisfactory tests and foundunsatisfactory shall be rejected or reheat treated (beginning with the solution heat treatment where applicable) in an acceptablefurnace, depending on the character of the failed tests. Alloys in which eutectic melting, and high temperature oxidation is foundshall be rejected and no reheat treatment permitted. Alloys that fail for reasons other than those enumerated above may be reheattreated.5.3.3 Test ReportsTe
