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Vol.36, No.12, 2091 ~ 2102, 1998
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| Title |
| Microstructure and Mechanical Properties of Mechanically Milled (Ti52Al48)100-xBx(X=0,0.5,2,5) Alloys |
| 정현호 , 표성규 , 황승준 , 김낙준 H . H . Chung , Sung G . Pyo , S . J . Hwang , Nack J . Kim |
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| Abstract |
| The present study is concerned with γ-(Ti_(52)Al_(48))_(100-x)B_x(x=0, 0.5, 2, 5) alloys produced by mechanical milling/vacuum hot pressing using melt-extracted powders. Microstructure of as-pressed alloys exhibit dual phase equiaxed microstructure of α₂ and γ with a mean grain size of 200 ㎚. Besides α₂ and γ phase, binary and 0.5%B alloys contains Ti₂AlN and Al₂O₃ phases located along the grain boundaries and show appreciable coarsening in grain and dispersoid sizes during annealing treatment at 1300℃ for 5 h. On the other hand, 2%B and 5%B alloys contains fine boride particles within the γ grains and show minimal coarsening during annealing. Room temperature compression tests of as-pressed alloys reveal low ductility, but very high yield strength >2100 ㎫. After annealing treatment, mechanically milled alloys show much higher yield strength than conventional PM and IM processed alloys, with equivalent ductility to IM processed alloys. 5%B alloy with smaller grain size shows higher yield strength than binary alloy at room temperature. When test temperature is increased to 850℃ 5%B alloy shows much lower strength than binary alloy, indicating the deformation of fine 5%B alloy is dominated by the grain boundary sliding mechanism. |
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