| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2000: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1999: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1998: ¥2,200,000 (Direct Cost: ¥2,200,000)
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| Research Abstract |
Cd, Zn and Mg single crystals were tested by [0001] tensile. {1122}<1123> second order pyramidal slip were activated in Cd and Zn single crystals by [0001] tensile test. Yields stress of each crystals increases with increasing temperature, namely anormalous temperature dependece. These values were lower than the case of [1120] tensile. In the case of Mg, second order pyramidal slip was activated in [1120] tensile. However, in the case of [0001] tensile, Mg single crystal were yield by {1012} twin. To investigate the effects of alloy element for pyramidal slip, Mg-3.5, 7,5, 8.6, 10.6 and 13.8at%Li alloy single crystals were tested by [1120] tensile in a range from 77K to 293K.Yield stress of second order pyramidal slip were decreased with increasing Li addition. Shear strains in slip bands of the pyramidal slip were increase with Li contents.. It is consider that mobility of (c+a) edge dislocation in second order pyramidal slip becomes high by Li addition. In Ti single crystals, prismat
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ic slip were occured by [1120] tensile in the range from 77K to 293K.In the case of [0001] tensile, Ti crystals which have low oxygen contents (1300at.ppm) yields by{1012} twin, however, Ti crystals with 4300at.ppm oxygen contents yield by {1011}<1123> first order pyramidal slip. Therefore, The pyramidal slip in Ti
will be active at higher oxygen contents.
In molecular dynamics simulation using Lennard-Jones (L-J) potential, (c+a) edge dislocation have perfect type core structure at OK.This core changed into two partial dislocations by applying strain and moved on second order pyraidal slip plane. At higher temperature, the core extended to basal plane and became sessile dislocation. In the case of EAM potentials, Mg and Be shows same results in L-J potential. The edge core of Ti have narrow core on {1122} and did not move on the slip plane. Core of (c+a) screw dislocation extended on two {1011} plane at OK.The core extended to {1122} plnae at higher temperature. The screw core were moved between {1122} and {1011} by double cross slip. These resutls were obtained in both potentals. From simulation resuls, deformation process by secondary pyramial slip will summarized as follows : (c+a) edge dislocation becomes sessile core structure with increaseing tempreture, then double cross slip of (c+a) screw dislocation occures to propagete slip bands. Less
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