Ductile-Phase Toughening of Brazed Joints

A heat treatment is presented that uses ductile-phase toughening to mitigate the effect of brittle intermetallics in a Ni-based braze alloy. The fracture resistance has been enhanced by creating a microstructure containing elongated ductile γ-(Ni) domains that align, preferentially, across the joint. The development of this beneficial microstructure is based on an understanding of the transient dissolution, isothermal solidification, and coarsening phenomena. Due to slow kinetics, the elimination of intermetallics by diffusion is avoided in favor of ductile domain formation through solidification control. The toughening has been attributed to a combination of bridging and process zone dissipation, enabled by the ductile phase

Micromechanical models to guide the development of synthetic 'brick and mortar' composites

This paper describes a micromechanical analysis of the uniaxial response of composites comprising elastic platelets (bricks) bonded together with thin elastic perfectly plastic layers (mortar). The model yields closed-form results for the spatial variation of displacements in the bricks as a function of constituent properties, which can be used to calculate the effective properties of the composite, including elastic modulus, strength and work-to-failure. Regime maps are presented which indicate critical stresses for failure of the bricks and mortar as a function of constituent properties and brick architecture. The solution illustrates trade-offs between elastic modulus, strength and dissipated work that are a result of transitions between various failure mechanisms associated with brick rupture and rupture of the interfaces. Detailed scaling relationships are presented with the goal of providing material developers with a straightforward means to identify synthesis targets that balance competing mechanical behaviors and optimize material response. Ashby maps are presented to compare potential brick and mortar composites with existing materials, and identify future directions for material development. (C) 2012 Elsevier Ltd. All rights reserve

The Equity Premium: Consistent with GDP Growth and Portfolio Insurance

We find that the long-term equity premium is consistent with both GDP growth and portfolio insurance. We use a supply-side growth model and demonstrate that the arithmetic average stock market return and the returns on corporate assets and debt depend on GDP per capita growth. The implied equity premium matches the U.S. historical average over 1926-2001. Separately, we find that the equity premium tracks the value of a put option on the S&P 500. Our theory predicts a smaller equity premium in the future, assuming that the recent regime shifts in dividend policies, interest rates, and tax rates are permanent. Copyright 2006, The Eastern Finance Association.

Herschel observations of ortho- and para-oxidaniumyl (H2O+) in spiral arm clouds toward Sgr B2(M)

International audienc