EFFECTS OF Cr ON THE LONGTIME EMBRITTLEMENT OF ALLOY 718

Current studies of high temperature materials have focused on the longtime behavior of materials in an effort to extend the life of service components. High temperature materials which appear to be stable in short exposure times can become unstable when exposed in a temperature range of up to 1200°F for times of 10,000 to 100,000 hours. Most alloys used in this temperature range are high Cr alloys and the superalloy most commonly used is alloy 718. Whether alloy 718 is used in aerospace or other industrial applications, the behavior of Cr on the formation of carbides,sigma phase, or other Cr rich intermetallic phase plays an important role in the eventual embrittlement of the material.Alloy 718 is limited to temperatures of 1200°F or below because of the occurrence of large amounts of transformations of the strengthening phase γ′to the delta plate phase with the resultant loss of impact and yield strength.In ongoing longtime behavior studies of alloy 718 at 1200°F,the impact property of alloy 718 drops from 38 ft-lbs to less than 8 ft-lbs in exposures of 50,000 hours. The initial drop in impact occurs without apparent changes in the strengthening phase; however, an αCr phase is starting to form and grows with time of exposure.The results of a study of the role of αCr on the longtime embrittled engine run turbine disks and isothermally exposed alloy 718 will be presented. The factors which affect the αCr formation will be discussed.

Longtime Couples Tell Their Story: An Integrated Constructivist View of Marital Relationships

The current study was designed to explore how longtime couples understand and manage their marital relationships into later time of their lives.An integrated approach of social exchanged and symbolic interactionism was adopted to understand how longtime couples develop,organize,and adjust their experience of marriage via active exchange and interactions.Participants were five Caucasian heterosexual couples who have been married for more than 18 years.A narrative interview was conducted on each couple separately.Participants were asked to tell a story of how their marriages started and developed in time jointly.Four major processes emerged from the current study displayed how longtime couples proactively engage in managing their life together as a union.The current study revealed a series of exploratory results concerning how individuals in marital relationships communicate and cooperate with each other in the process of their marital relationship development.It also identified an interesting point of view concerning how couples actively manage their negative experiences regarding critical transitioning life events related to their marriage.This adds evidence to understand and predict marital outcomes from a micro-social constructivist approach.Implications about couples and family counseling from a social-constructive approach,as well as the probability of synthesizing a social-constructivist family framework with a systemic family framework,are thus provided.

THE WELL-POSEDNESS AND ASYMPTOTICS OF MULTI-DIMENSIONAL QUANTUM HYDRODYNAMICS

The multi-dimensional quantum hydrodynamic equations for charge transport in ultra-small electronic devices like semiconductors, where quantum effects （like particle tunnelling through potential barriers and built-up in quantum wells） take place, is considered in the present paper, and the recent progress on well-posedness, stability analysis, and small scaling limits are reviewed.

Trajectory Attractors for Binary Fluid Mixtures in 3D

Two different models for the evolution of incompressible binary fluid mixtures in a three-dimensional bounded domain are considered.They consist of the 3D incompressible Navier-Stokes equations,subject to time-dependent external forces and coupled with either a convective Allen-Cahn or Cahn-Hilliard equation.Such systems can be viewed as generalizations of the Navier-Stokes equations to two-phase fluids.Using the trajectory approach,the authors prove the existence of the trajectory attractor for both systems.

On a Class of Generalized Curve Flows for Planar Convex Curves

In this paper,the authors consider a class of generalized curve flow for convex curves in the plane.They show that either the maximal existence time of the flow is finite and the evolving curve collapses to a round point with the enclosed area of the evolving curve tending to zero,i.e.,limt→T A(t)=0,or the maximal time is infinite,that is,the flow is a global one.In the case that the maximal existence time of the flow is finite,they also obtain a convergence theorem for rescaled curves at the maximal time.

A LOCAL ATTRACTOR FOR A NONLINEAR WAVE EQUATION ARISING IN ELASTIC WAVEGUIDE MODEL

This paper studies the asymptotic behavior of solutions to the initial boundary value problem for a nonlinear wave equation arising in an elastic waveguide model. It proves that under rather mild conditions on g the related solution semigroup possesses a local attractor.