Vol.5 No.1 2012

Research paper : An analysis method for oxygen impurity in magnesium and its alloys (A. Tsuge et al.)−31−Synthesiology - English edition Vol.5 No.1 (2012) the IGF-IRA and CPAA methods. For the analysis value of sample no.3, the value for IGF-IRA was slightly lower than that from CPAA. From the analysis principle of CPAA, the cause of discrepancy was considered to be the fact that the CPAA detects every oxygen in the sample, even that in water, while the IGF-IRA measures only the oxygen in the form of stable oxides. Particularly, in sample no.3 it is inferred that a stable oxide is not formed because of incomplete oxidation by moisture and that water and hydroxides are contained. Considering these situations, it was asserted that the analysis values of the CPAA and IGF-IRA methods agree within the standard deviations for samples no.1 and no.2, which were not affected by moisture. As a result, the validity of the analysis value of IGF-IRA was considered to be confirmed.3.2 Applicability range of IGF-IRA for Mg alloyFor Mg alloys, there are many reference materials with known alloy composition and impurity content distributed by several companies. However, there are no reference materials with certified oxygen content. Therefore, we investigated only whether there would be any problems in the measurement procedure of the IGF-IRA method using the commercial reference materials. As a result, as shown in Table 2, the procedure was applicable to most of the commercially available Mg alloys excluding some exceptional troubles in the following. For the samples containing more than 6 % aluminum, after the Mg was evaporated off from the eutectic compound, the residual Sn was found to adhere to the crucible. Furthermore, with increase in aluminum content to more than 9 %, the Sn adhered to a wide area at the bottom of the crucible. This is attributed to the fact that the aluminum tended to form carbide which has good wetness against carbon. Since the residue could be removed by the disruption of the crucible, it was recognized in this standardization that our method is commonly applicable to commercially available Mg alloys. 3.3 Applicability range of the analysis deviceThe analysis devices of the inert gas fusion method are supplied from two companies; one in Japan and the other overseas. There are, however, various models according to their manufacturing year. In standardizing a method using an analysis device, a standard must include as many manufacturers and models of the analysis device used in industry as possible. Therefore, we called for participants in Japan to conduct joint analysis tests. For the analysis devices of the different manufacturer from that of our device, the analysis conditions such as applied power and heating time that suited the device were disclosed through cooperation from the manufacturer. Using the sample described in 3.1, we specified the heating condition according to the voltage applied to the graphite crucible.The results of the above experiment and the CPAA analysis described in 3.1 are shown in Table 3. Here, the values of Table 2. Applicability of IGF-IRA to various alloysTable 3. Result of the joint analysis test in JapanTable 1. Comparison of the analysis results between the inert gas fusion method and the CPAA methodFig. 11 Analysis flow diagram for CPAA Removal of surface contamination by etchingAnalysis and determinationRadiation measurementActivation of the sampleChemical separation of measured element0.0600(mass%)0.0480±0.0052 (mass%)0.0180(mass%)0.0165±0.0023 (mass%)0.0001(mass%)0.0006±0.0005 (mass%)No.2No.3No.1CPAA methodInert gas fusion methodSample no.Al(approx.12 %),Zn(approx.1 %),Ca(approx.1 %)Commercial AZX1211Al(approx.6 %),Mn(approx.0.1 %),Ca(approx.2 %)Commercial AMX602 Zn(approx.6 %),Zr(approx.0.7 %)Commercial ZK61a Al(approx.6 %),Mn(approx.0.1 %)Commercial AM60b△(Adhesion of molten material)△(Adhesion of molten material)△(Adhesion of molten material)△(Adhesion of molten material)Al(approx.9 %),Zn(approx.1 %)Commercial AZ91Al(9.5 %),Si(1.1 %)HMP STD1/85○Al(4.1 %),Zn(0.2 %),Mn(0.4 %),Si(1.2 %)HMP A-41-T05○Zn(0.5 %),Mn(0.1 %),Nd(2.4 %),Gd(1.5 %)BulkBulkBulkBulkBulkBulkBulkBulkMBH C69XMgy4-a○Ag(2.05 %),Rare earth(2.4 %)MBH C68XMgh40○Zn(5.47 %),Th(1.85 %)MBH C67XMgg40○Rare earth(2.4 %),Zn(3.18 %)MBH C67XMgf30○Zn(6.81 %),Mn(0.166 %)MBH C66XMgc40△(Adhesion of molten material)Al(6.01 %),Zn(0.411 %)MBH C65XMga50○Mn(2.36 %)MBH C63XMge30○MBH C61XMgp30○○○ChipChipChipChipChipChipChipChipMBH C61XMgp10Yes/no of analysis (○: yes, △: problem, ×: no)Alloy composition (concentration)FormName of sample--0.06000.0480Bumping0.04920.0021No.30.01800.0165Bumping0.02120.0015No.20.00010.0006Bumping0.0014NDNo.1Charged particleAnalysis lab DAnalysis lab CAnalysis lab BAnalysis lab ASample


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