Heterogeneous Deformation Behavior Research Articles

In situ neutron diffraction study of α–γ Fe–Cr–Ni alloys under tensile deformation

Neutron diffraction experiments were performed in situ upon tensile loading for five Fe–Cr–Ni alloys with different ferrite volume fractions ranging from 0 to 100%. The diffraction profiles were recorded along with the tensile deformation curves during temporary stops in a deformation machine (5 ks each) with the crosshead fixed. One reflection of each phase, (111) of austenite (γ) and (110) of ferrite (α), respectively, were measured simultaneously by using a position sensitive detector. Evolution of elastic lattice strains and dislocation densities in both constituent phases was evaluated from measured diffraction profiles as a function of external loading. Based on these experimental results, heterogeneous deformation behavior in the α–γ dual-phase alloys is discussed.

K-0335 均質化法に基づくTRIP鋼の変形挙動の数値シミュレーション(G01-4 変形解析)(G01 計算力学部門一般講演)

The transformation-induced plasticity (TRIP) steel possesses such favorable mechanical properties as tenacity and strength due to strain-induced martensite transformation. This excellent mechanical properties of TRIP steel depend on inhomogenious morphology of martensite in microscopic region. However, to evaluate the effect of microscopic morphology of martensite on its mechanical properties, it is difficult to express microscopically its heterogeneous deformation behavior by a conventional FEM. Here, the computational simulation of deformation behavior of TRIP steel is performed by recently developed homogenization method.

TEM study on lamellar microstructure and α2/ γ interfacial structure in a hot-deformed two-phase γ-TiAl-based alloy

The hot deformation behavior of the lamellar microstructure in a Ti–45Al–8Nb–2.5Mn–0.05B alloy has been studied by transmission electron microscopy (TEM). Numerous subgrain boundaries and two types of deformation twins were frequently observed in the hot-deformation-induced lamellae. The occurrence of nonequilibrium semi-coherent α 2/ γ interfaces is an important microstructural feature of hot-deformed lamellar microstructure in a similar Ti–45Al–10Nb–2.5Mn–0.05B alloy. The distinctiveness of these α 2/ γ interfaces is the misorientation from the conventional α 2/ γ orientation relationship {111} γ ‖{0001} α2 , 〈11̄0〈 γ ‖〈112̄0〉 α2 , as well as the asymmetry in the sense of interfacial boundary planes deviating from the equilibrium atomic planes (111) γ or (0001) α2 . Numerous interfacial ledges containing 1/3[111] Frank partial dislocations exist in this nonequilibrium semi-coherent α 2/ γ interface. The analyses point out that, in the hot-deformation-induced bent lamellae, the 1/3[111] Frank partial dislocations in the ledges of α 2/ γ interfaces can be formed by reactions between the matrix and interfacial dislocations. This type of semi-coherent α 2/ γ interface is formed in order to accommodate the relative rotation of α 2 and γ plates resulting from their heterogeneous deformation behavior. In the sharply bent lamellae, there even occur largely misoriented, non-coherent α 2/ γ interfaces with the {111} γ plane no longer being parallel to the {0001} α2 plane, resulting from the lamellae bending/kinking during heavy deformation. At these nonequilibrium, non-coherent α 2/ γ interfaces with high interfacial strain energy, the T(Q) deformation twins, being inclined to the lamellar interface, are observed to be preferentially formed. The process is favored by the localized stress field of the interfacial misfit dislocations.