Nobukatsu Fujino, Kazuo Yamanaka and Junichiro Murayama. Central Research Laboratories, Sumitomo Metal Industries, Ltd. Amagasaki, Japan.

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1 ION MICROPROBE ANALYSIS OF HYDROGEN AND OXYGEN IN TITANIUM Nobukatsu Fujino, Kazuo Yamanaka and Junihiro Murayama Central Researh Laboratories, Sumitomo Metal Industries, Ltd. Amagasaki, Japan Introdution It is well known that metallurgial properties of titanium are severely influened by trae elements. The quantities of those elements are usually determined as average omposition by means of hemial analysis method. However, the trae elements are often loalized during heat treatments and deformations. The eletron probe miroanalyser (EPMA) is very useful instrument.for miroanalysis of elements and many metallurgial problem has been revealed. Reently, ion miroprobe mass analysers (IMMA) have been developed and the IMMA is applied to hydrogen and oxygen analysis in titanium. Hydrogen in titanium hydride (TiH) an be diretly observed and also quantitative analysis of hydrogen in titanium is developed. The IMMA was also applied to surfae analysis of oxide layer on titanium and depth-profile of oxygen was obtained. Ion Miroprobe Mass Analyser (IMMA) The IMMA have a few unique features as follows: (1) High sensitive miroanalysis of lm order (2) High sensitive surfae analysis and also in-depth analysis (3) Miroanalysis of hydrogen In Fig.1, a shemati diagram of the IMMA is shown. Primary ion beam through an energy separating setor is foussed on a speimen and seondary ions are sputtered from the speimen. These seondary ions are analysed by double fousing mass spetrometer and intensity of the seondary ions are reording as digital ount or ion beam s.anning image mapping. In the ase of in-depth analysis, the seondary ion intensity of analysed element is memorized by a multi-hannel saler. In the present paper, representative appliation results of IMMA to titanium are mentioned. Hydrogen Analysis Titanium hydride has been identified from relationship between the quantity of preipitation in metallurgial mirograph and hydrogen omposition.

2 2012 N. Fujino et al. Fig.1 Shemati diagram of the ion miroprobe mass analyser (ARL) In the present work, hydrogen in the hydride an be diretly determined by the IMMA. In the IMMA analysis, primary ion beam (o;) bombards on sample surfae, and the sample is sputtered and the seondary ions is emitted. During the primary beam sans on the sample, a point in the analysed area is momentarily bombarded and r'lpeated. Fig.2 shows that the seondary ion (H+) intensity relating to time from titanium ontaining 32 ppm(wt.) hydrogen when the primary ion beam is fixed at a point. The beginning peak of H+ intensity is thought to be sputtering of adsorbed hydrogen and the H+ ion intensity dereases to onstant value. After ut off period, the pl.enomena is repeated. Z' ;;.. : i::" g 8... J: (seond lime) -----t -+I..,..,,.., Primaryiol--o-----Bombordlng Bombarding beam Cutting Fig.2 Hydrogen ion intensity from Ti (32 ppm H), repeating of primary ion bombarding and utting off. oll O, 20KV-inA (100 80)

3 ION MICROPROBE ANALYSIS OF HYDROGEN AND OXYGEN 2013 In the sam.ple hamber of IMMA, vauum ondition is 10-8 torr order and it is not enough to avoid adsorption of H 2 0 whih is soure of H+ seondary ion, as shown in Table 1. It is neessary that the adsorbed H 2 o is dereased in the ase of hydrogen analysis, and a old-plate ooled to liquid nitrogen temperature is used. Ion Fresh 3005eCut,H K +180 K K + Qt. K 13CH K + 02 K 110H K K Table 1 Relative intensity of ion from Zironium surfae before and after adsorption o+, 20KV-2nA (100 '" x 100 "'"' ) 2 In Fig.3, influenes of adsorption are shown using titanium, zironium and iron. Effetiveness of old plate (C.P.) using liquid nitrogen are also reognized in Fig.3. KC <C--- Fe (,p.unused) +-- Ti (.p. us.d) +-- Zr (.p, used ) Fig.3 Adsorbed hydrogen vs. adsorbing time and effet of old plate o;,. 20KV-2nA (31'-"'t Feo(.pused) :::::, } Cleaned ott leveot "' L ' Adsorbing time (seond)

4 2014 N. Fujino et al. Fig.4 shows the relation between H+ intensity from titanium ontaining 32 ppm(wt.) hydrogen and urrent density of primary ion beam, hih is beam urrent devided by analysed area. The normalized H intensity dereases with average urrent density and reahes to a onstant level. 100 I ---,,-.-._ o Cold Plate-Room Temp. Fig.4 Effet of urrent density and old plate on Ti (H = 32 ppm) o+, 20KV-1-25nA (100"''" x 100 "''") 2 ColdPl11te-oLNTemp CurrPnt(f1A) rrb'!s1\y('nm'l-..;>o This fat means that higher primary ion intensity dereases the adsorbed hydrogen (=vapor), and the relation may be expressed by the following equation. I = Ib + Ki ( 1) Where I is the seondary H+ ion intensity, Ib is the bakground H intensity aused by adsorbed hydrogen(vapor), i is urrent density, and K is a parameter to hydrogen ontent. From eq.(1), I/i = Ib/i + K (2) The hydrogen ontent CH is given by the following equation. CH = I-Ib -.-.k l. I.p Fig.4, effets of the old-plate (C.P.) and urrent density upon H intensity are generalized. (3)

5 ION MICROPROBE ANALYSIS OF HYDROGEN AND OXYGEN Titanium hydride (TiH) Fig.5(a) is optial mirophotograph of titanium hydride (TiH) in titanium ontaining 950 ppm(wt.) hydrogen. Fig.5(b) is the step-san analysis results of H+ intensity. Fig.5() shows the H+ ion image. The hydrogen in titanium hydride preipitate is diretly determined by the IMMA. (a) Mirophotograph of TiH (b) SteP+san analysis of H () H+ ion image 401' 2. Zironium hydride (ZrH) Fig.5 Hydrogen analysis of TiH in Ti (H = 950 ppm) + o 2, 20KV-3.5nA Step-san Pre-sputtering 5se, measuring time 1se Similar experiment is applied to zironium hydride and hydrogen is determined as shown in Fig.6. S/N2.15 I <20> µ /I l Se. A I\ I\,,, I I.,.,.../. V -..J.- 50 fl Mirophotograph of ZrH J 1 KC/Se Step-san analysis of H+ Fig.6 Step-san analysis of H+from ZrH in Zr (H = 100 ppm) + o 2, 20KV-3.5nA, 1se/1 step

6 2016 N. Fujino et al. 3. Quantitative analysis of hydrogen in titanium Intensities of seondary hydrogen ion H+ are shown in Fig.7 using NBS Ti-H series, in whih there is no segregation of hydrogen. In Fig.8, the working urve of hydrogen in titanium and the influene of adsorbed vapor are shown. I H--:-1-,; 1,r;,;_,+J-!-\-1-H-- '-I.. I :.. if [ f:. I! (1..,.j,.,., I I I <lff!fi i I..-':!' I Fig.7 Hydrogen analysis of NBS Ti-H series + m m o 2, 20KV-20nA (50 x 4o ) old plate used Hydrogen in titanium (ppm) Fig.8 Calibration urve of H Analysis of Surfae Oxide Layer When titanium is heated in air, surfae of the titanium is oxidized and olored, it is important to know the relationship between the oxide layer thikness and the olor. The oxide layer is analysed by the IMMA with the modf of in-depth analysis. Using N + 2 primary ion beam, seondary ion 0 intensity indiates the thikness of oxide layer as shown Fig.9. In Fig.10, relation between the thikness of oxide layers and the heating onditions are shown. However, the IMMA is time-onsuming instruments to analyse, then eletron miroprobe analysis is developed for routine analysis. Intensity of OK obtained by the EPMA gives the finite-thikness of oxide layer as shown in Fig.11. In the ase of high temperature and long time heating of titanium, thik oxide layer is formed and diffusion of oxygen an be observed by metallographi mirophotograph as shown in Fig.12(alStrutures of heated titanium are identified by X-ray diffration, IMMA, EPMA and Vikers mirohardness test. These results are shown in Fig.12 (b) and Fig. 12 ( )

7 ION MICROPROBE ANALYSIS OF HYDROGEN AND OXYGEN 2017,., ;;; :s 0 t Surfae As QQ CX SQHr 30Q Cx SQHr 500 C xsqhr Surfae 3000 Surfae 3000 Surfae 3000 Oepth(A) Fig.9 Measurements of oxide layer thikness on titanium by IMMA (Pri. ion ; N; ) "' t,.,.. 0 ' ;:: g 1000 As JOO & ( ) x50hr Fig.10 Relationship between Ti-oxide layer thikness by IMMA and heat temperature Heat ondition in air 200 at 15KV at 30KV Fig.11 Relationship between Ti-oxide layer thikness and OK intensity by EPMA Ti-oxide layer thikness (fj)

8 2018 N. Fujino et al. Ti mtro struture (1000 X 10!..!_n Air) (a) IOOO"t X IOHr in Air 1000 x 10Hr in Air >.. :i:: Weight SOg.. Ti,, Dopth(p) (b) () Fig.12 Metallographi mirophotograph, EPMA analysis and Vikers mirohardness measurement of titanium oxide layer for high temperature and long time heating in air. a b Cross-setion mirophotograph of titanium oxide EPMA line analysis Vikers mirohardness measurement

9 ION MICROPROBE ANALYSIS OF HYDROGEN AND OXYGEN 2019 Conlusion For loal analysis of hydrogen in titanium, ion miroprobe analysis was applied. Hydrogen in titanium hydride was diretly determined by the IMMA and zironium hydride in zironium was also deteted. Quantitative analysis of hydrogen in titanium was developed and a pratial working urve was obtained. In-depth analysis using IMMA was applied to deide the relationship between the absolute thikness and heating onditions for thin oxide layer and olor on titanium surfae. Based on the absolute thikness, pratial working urve for thikness was obtained from OK intensity using EPMA. Referenes 1) H. Lieble, J. Ard. Phys., 38, 5277 (1967) 2) T. Shiraiwa et al., Sumitomo Metal, 26, 470 (1974) 3) T. Shiraiwa et al., Rept. of Japan So. Promot. Si. No.145 Comittee, Tokyo, JSPS, ) N. Fujino et al., Titanium-Zironium, 27, 74 (1979) 5) ibid 26, 198 (1978)

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