1989 Fiscal Year Final Research Report Summary
Composite precipitation and improvement of ductility in Al-Li-Ti alloys
| Project/Area Number |
63550538
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
金属材料(含表面処理・腐食防食)
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| Research Institution | Osaka University |
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Principal Investigator |
SAJI Shigeoki Osaka University, Faculty of Engineering, Associate Professor., 工学部, 助教授 (60029072)
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| Project Period (FY) |
1988 – 1989
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| Keywords | Al-Li-Ti alloy / composite precipitate / ductility / delta-Al_3Li / deformation mode / mechanical alloying / amorphous / Al-Ti mixed powder |
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| Research Abstract |
Composite precipitates consisting of the core particle,presumably Al (Li, Ti) and the outer shell of delta-Al_3Li phase were formed by a two-stage aging ( at 500ﾟC and then at 180 or 190ﾟC) in chill cast specimens of Al-(1.6-2.3)wt% Li-(0.45-0.95)wt%Ti alloys, Al-Li-Ti ternary alloys containing both the composite precipitates and particles in the peak-aged condition, showed a considerably superior ductility to that of the peak-aged Al-Li binary alloy together with a higher strength. Bow-out dislocations and tangled dislocations were observed near the composite precipitates in the tensile-strained specimens of Al-Li-Ti alloys containing the composite precipitates and shear type of transgranular fracture were recognized in SEM fractografy. On the other hand, planar slip of dislocations and typical intergranular fracture were observed in the peak-aged specimens of Al-Li binary alloys. The composite precipitates improve ductility by retarding the planar slip mode in Al-Li-Ti alloys.
Alloying processes, formation of amorphase phase and hardening of Al-20 wt% Ti mixed powders during mechanical alloying by Attritor type of ball mill, have been investigated. The following results were obtained: A mechanical alloying process of flake-forming, cold welding of the flaked powders, fracturing of the composite powders, forming of solid solution and amorphous phase was detected. Remarkable increase in hardness of the mixed powders during MA were explained in terms of solid solution hardening by titanium, dispersion hardening of Al_2O_3, work-hardening and hardening by refinement of crystal grains of aluminum.
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