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Table I. Some iron, chromium, and nickel along with small amounts of oxygen, nitrogen, and carbon were found in the mechanically alloyed powders. Figure 1 shows differences between the X-ray diffraction patterns from AI-12 at. pct Ti as-mixed powders and mechanically alloyed powders processed for the indicated times. The disappearance of the titanium diffraction peaks shows that alloying of titanium atoms in the aluminum matrix is almost complete after 72 ks of milling. The broadening of the peaks and decrease in the peak heights during further milling corresponds to the refining of the crystal size and the increase in the crystal strainY sD Figure 2 shows diffraction patterns of the mechanically alloyed AI-Ti-Fe composite powders (360 ks at 150 g) containing about 12 at. pct Ti and with iron compositions in the range of 0.1 to 6.98 at. pct. The details of chemical compositions of these mechanically alloyed powders are shown in Table II. The diffraction peaks become weaker and broader with increasing iron content in the mechanically alloyed powders, and the peak position of AI(111) clearly shifts to a higher angle with iron content. These results indicate that iron atoms as well as titanium atoms dissolve in the aluminum-rich matrix to some extent, although it is reported that iron does not dissolve in the face-centered cubic aluminum phase in the AI-Fe binary system during MA. I~~ All the diffraction peaks from the A1-Ti-Fe solid solution disappear for A1-12 at. pct Ti-7 at. pct Fe mechanically alloyed powders. A broad and weak peak may be present that would be associated with an amorphous structure. Many

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(d) SHIGEOKI SAJI, formerly Associate Professor, Department of Materials Science and Engineering, Faculty of Engineering, Osaka University, Suita 565, Osaka, Japan, is Professor, with the Department of Materials Science and Engineering, Faculty of Engineering, Toyama University, Toyama 930, Japan. YUTAKA NEISH1, Graduate Student, HIDEKI ARAKI, Research Associate, and YORITOSHI MINAMINO, Assistant Professor, are with the Department of Materials Science and Engineering, Faculty of Engineering, Osaka University, Suita 565, Osaka, Japan. TOSH1MI YAMANE, Professor, is with the Department of Mechanical Engineering, Hiroshima Institute of Technology, Hiroshima 731-51, Japan. Manuscript submitted June 21, 1994. METALLURGICAL AND MATERIALS TRANSACTIONS A

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Fig. l - - C h a n g e s in X-ray diffraction patterns obtained from asmixed and mechanically alloyed powders of the Al-12 at. pct Ti sample. Milling times are indicated for each pattern: (a) as-mixed and (b), (c), (d), and (e) mechanically alloyed at 150 g for 72, 216, 720, and 1440 ks, respectively.

VOLUME 26A, MAY 1995-- 1305

Table I. Chemical Composition of Elemental Aluminum, Titanium, and Iron Powders and Various Mechanically Alloyed Al-12 At. Pct Ti Composite Powders in Atomic Percent Sample

Ni

Cr

Mn

Si

O

N

C

Fe

Ti

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