Harmonic Structure (HS) has a heterogeneous microstructure consisting of bimodal grain size together with a controlled and specific topological distribution of fine and coarse grains. In other words, the HS is heterogeneous on micro- but homogeneous on macro-scales. The most unique feature of HS is its continuously connected UFG Shell structure. In the present work, the HS design has been applied to pure metals and alloys via SPD powder metallurgy process. At a macro-scale, the harmonic structure materials exhibited significantly better combination of strength and ductility, as compared to their homogeneous microstructure counterparts. This behavior is essentially related to the ability of the HS to promote a large strain hardening and uniform distribution of strain during plastic deformation, leading to improved mechanical properties by avoiding or delaying localized plastic instability. Such outstanding mechanical properties of HS materials are attributed to the continuously connected UFG-Shell structure. This unique microstructure provides stress-concentration in the micro scale and stress dispersion in the macro scale.

Flowability and packing structure of metallic powder are ones of key issue to achieve good formability of additive manufacturing. In this article, packing structure of metallic powders is studied using two kinds of gas-atomized ferric powders and two kinds of model powders. The packing fraction of the powders is increased by tapping. The packing behavior by tapping is different depending on characteristics of powder. Larger angle of repose is observed for the powder with higher packing fraction after the tapping. Since fine powder penetrates into the opening gaps located in the coarse powder, high packing fraction can be achieved by mixing of the coarse powder and fine powder. Moreover, stacking behavior of powder bed with these powders is also investigated using handmade additive manufacturing machine. Obtained data allowed us to discuss the formability of additive manufacturing.

In this paper, the fracture problem of a functionally graded thermal barrier coating (FGTBC) containing a crack parallel to the interface between the FGTBC and a homogeneous substrate is considered. The problem is solved for the laminate that is suddenly heated from the upper surface of the FGTBC. The bottom surface of the homogeneous substrate is maintained at the initial temperature. The crack faces are supposed to be completely insulated. Material properties are assumed to be exponentially dependent on the distance from the interface. By using both the Laplace and Fourier transforms, the thermo-mechanical fracture problem is reduced to a singular integral equation and a system of singular integral equations which are solved numerically. The stress intensity factors of the crack are computed and presented as a function of the normalized time for the various values of the nonhomogeneous and geometric parameters.