ASTM_B_923_-_16.pdf

Designation:B92316Standard Test Method forMetal Powder Skeletal Density by Helium or NitrogenPycnometry1This standard is issued under the fixed designation B923;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.1.Scope*1.1 This test method covers determination of skeletal den-sity of metal powders.The test method specifies generalprocedures that are applicable to many commercial pycnom-etry instruments.The method provides specific sample outgas-sing procedures for listed materials.It includes additionalgeneral outgassing instructions for other metals.The ideal gaslaw forms the basis for all calculations.1.2 This test method does not include all existing proce-dures appropriate for outgassing metal materials.The includedprocedures provided acceptable results for samples analyzedduring an interlaboratory study.The investigator shall deter-mine the appropriateness of listed procedures.1.3 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.3.1 State all numerical values in terms of SI units unlessspecific instrumentation software reports volume or density,orboth,using alternative units.In this case,present both reportedand equivalent SI units in the final written report.Manyinstruments report skeletal density as g/cm3instead of usingcorrect SI units(kg/m3).1.4 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:2B215 Practices for Sampling Metal PowdersB243 Terminology of Powder MetallurgyE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3.Terminology3.1 Definitions:3.1.1 Refer to Terminology B243 for additional definitionsrelating to metal powders.3.2 Definitions of Terms Specific to This Standard:3.2.1 density,nthe mass per unit volume of a material.3.2.2 density,skeletal,nthe ratio of mass of discretepieces of solid material to the sum of the volumes of the solidmaterial in the pieces and closed pores within the pieces.3.2.3 outgassing,nthe evolution of gas from a material ina vacuum or inert gas flow,at or above ambient temperature.3.2.4 skeletal volume,nthe sum of the volumes:the solidmaterial in the pieces and closed pores within the pieces.4.Summary of Test Method4.1 An appropriately sized sample(to provide at least theminimum skeletal volume required for reliable results for theinstrument or apparatus used)is outgassed under appropriateconditions prior to analysis.4.2 The sample is weighed to nearest 0.1 mg.It is importantto use an analytical balance to determine the sample mass.Thepycnometer measures the total displaced skeletal volume of thesample under analysis.The sample mass is then used tocalculate the skeletal density of the metal.Any error in thesample mass will affect the calculated density.Some cleaningof the sample surface may take place inside the pycnometer.Therefore,it is best to reweigh the sample after analysis anduse the final mass when calculating skeletal density.4.3 Sample skeletal volume is determined a minimum offive times.Skeletal volume average and standard deviation arecalculated using standard statistical methods.4.4 Calculations are based on the ideal gas law,as requiredby the instrument being used for the determination.Theassumption of ideal behavior is accepted as valid at analyticaltemperatures and pressures.For instruments designed with twopressure chambers,one a sample compartment,and the other agas expansion chamber,the equation for sample volumecalculation takes the form:1This test method is under the jurisdiction of ASTM Committee B09 on MetalPowders and Metal Powder Products and is the direct responsibility of Subcom-mittee B09.03 on Refractory Metal Powders.Current edition approved Oct.1,2016.Published October 2016.Originallyapproved in 2002.Last previous edition approved in 2010 as B92310.DOI:10.1520/B0923-16.2For 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 Vsample5 Vcell2 VexpSP2P12 P2D(1)where:Vsample=calculated sample volume,Vcell=calibrated sample compartment volume,Vexp=calibrated expansion volume,P1=measured gas pressure when only Vcellis filled withanalysis gas,andP2=measured gas pressure aft