Effects of high temperature fatigue on microstructure and mechanical properties of a nickel-base precipitation hardened alloy

Effects of high temperature strain controlled push-pull fatigue on the microstructure and mechanical properties of a nickel-base precipitation hardened alloy were studied. The fatigue deformation alone at 700 °C did not impair the mechanical properties of this alloy; however, a hold period ranging from one minute to one hour at tension-peak decreased the tensile ductility and the fracture toughness significantly. This was mainly attributed to grain boundary cavitation. Continuous fatigue resulted in dislocation bands, whereas hold-time fatigue caused a coherency loss iny’ precipitates. Implications of these microstructural changes for the residual mechanical properties are discussed. Formerly with the Brookhaven National Laboratory, Upton, NY 11973. Formerly with the Brookhaven National Laboratory.     

基于干旱区气候考虑的建筑群体空间设计研究

为解决我国西部干旱地区的诸多规划问题,探索了干旱地区一般的建筑群体空间设计经验。针对干旱地区的气候特征,在建筑群体选址和建筑群体空间形态两个方面回应了适合干旱地区气候特征的设计要点。其设计要点具有一般性设计通则的特点,将普遍适用于干旱地区。