| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2002: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 2001: ¥3,000,000 (Direct Cost: ¥3,000,000)
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| Research Abstract |
To overcome weak points of past analytical methods to analyze microsegregation of alloys, a newly proposed progressive-type solidification equation was used to analyze the solidification path of Al-Ti-Cr alloys, and the following results were obtained. Liquid composition(C_<Li>) at the solid fraction(fs_i) of a region i is calculated from the data of (i-1) region by the progressive-type solidification equation : C_<Li>=C_<Li-1>・[{1-(1-B・k_<i-1>)fs_i}/{1-(1-B・k_<i-1>)fs_<i-1>}]^<(ki-1-1)/(1-Bki-1), where k_<i-1> is partition ratio at C_<Li-1>, B is given as follows : B=2α for Flemings model, B=2α(1-exp(-1/α)) -exp(-1/2α) for Clyne-Kurz model, B=2α/(1+2α) for Ohnaka model for plate-like dendrite, and α=D・θ_f/L^2, D : solid diffusion coefficient, θ_f : local solidification time, L : effective length of volume element(=s・d_2/2, s : structure factor(=0.5〜1)). The above modified equation enabled analysis of precise solidification path by using variable partition ratio(ki) from i=1 to n in the solidification range by dividing it with enough number(n) for the precise calculation. The solidification path of Al-Ti-Cr alloys were analyzed by the above progressive-type solidification equation by using experimentally obtained partition ratios(k_<Ti>, k_<Cr>), which are the functions of liquid compositions, and the calculated results agreed well with the experimental results. Further, temperature dependence of yield strength of L1_2-Al_<65>Cr_<10>Ti_<25> single crystal was investigated by compression test, and yield strength versus temperature curve showed a plateau or anomaly in the intermediate temperature range. Deformation-induced dislocation structure in the specimen was examined by transmission electron microscopy (TEM) to explain the above phenomena.
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