| Budget Amount *help |
¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1987: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1986: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Research Abstract |
The phenomenological crystallographic theory of martensitic transformations is well established. But, a perfect agreement between theory and experiment for a complete set of crystallographic parameters is rather rare, except for a {3,10,15}}transformation in fe-pt, fe-mn-c and fFe-Pt, Fe-Mn-C and Fe-Al-Cical" case in au-47,5at%cd alloy. Ane a.pectCin improvOng the agreement is to find out a correct lattice invariant shear. previously, twinningPmode as a lattice invariant shear was believed to be type i, whose twin pTane Iriginates from a mirror plane in the parent phase. but, type ii twinninB, whType IInning direction originates from a two-fold symmetry direction in the parent phase, is also geometrically possible. in the present invesIigation, we found that the theory perfectly applies to the beta_1 gamma<@21<@D21@>D2sforma<@D21@>D2 cu-al-ni alloy by inCu-Al-Nng<111>gamma: type ing<111>gamma; Type II twinning for all crystallographic parameters simultaneously measured. This is an alloy where theory and experiment were inconsistent previously. Similarly, we found that the lattice invariant shears in Ti-Ni and Cu-Sn alloys were Type II twinning, and that consistent agreements were obtained between theory and experiment for these alloys. However, in Au-Cd and Ag-Cd alloys, the lattice invariant shear were found to be type I twinning as previously reported. Thus, we found that both Type I and Type II twinning are present as lattice invariant shears, dependent upon alloy systems. Further-more, we found that we can get a good agreement between theory and experiment, if we choose a lattice invariant shear correctly from the phenomenological crystallographic theory.
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