Temperature Effects on the Tensile Properties of Precipitation-Hardened Al-Mg-Cu-Si Alloys
Because the mechanical performance of precipitation-hardened alloys can be significantly altered with temperature changes, understanding and predicting the effects of temperatures on various mechanical properties for these alloys are important. In the present work, an analytical model has been developed to predict the elastic modulus, the yield stress, the failure stress, and the failure strain taking into consideration the effect of temperatures for precipitation-hardenable Al-Mg-Cu-Si Alloys (Al-A319 alloys). In addition, other important mechanical properties of Al-A319 alloys including the strain hardening exponent, the strength coefficient, and the ductility parameter can be estimated using the current model. It is demonstrated that the prediction results based on the proposed model are in good agreement with those obtained experimentally in Al-A319 alloys in the as-cast condition and after W and T7 heat treatments.
The Effects of Solidification Cooling Rates on the Mechanical Properties of an Aluminum Inline-6 Engine Block
A shift from ferrous to aluminum alloys for use in automotive engine blocks has significantly reduced the weight of vehicles and has consequently improved fuel economy while reducing harmful emissions. During the casting process of aluminum engine blocks, chilling devices are typically incorporated into the sand castings for faster cooling and to allow for a more uniform cooling rate. The effects that chills have on the alloys microstructure (i.e. size, morphology and SDAS) and mechanical properties have been studied in this paper. This study characterizes the microstructure throughout a modified 319 type aluminum inline-six engine block using scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction. In addition, mechanical testing (i.e. uniaxial tensile testing) have been performed at various depths along the cylinder web to determine the effects that varying microstructure has on the mechanical properties of the alloy. The results from this study indicate that the minor variation in cooling rates led to a fine and relatively uniform microstructure; resulting in the observation of similar mechanical properties throughout the entire cylinder bridge.
Problems of a centralised department in a decentralised mental hospital.
Abstract This paper deals with some of the issues and problems which arose in a state mental hospital, when in the course of becoming a more community-oriented facility, the hospital decentralized its clinical structure into geographically-based treatment units while retaining a centralized nursing department administration. The effects of unitization and a subsequent attempt to reoganize the nursing department on both the character of professional roles and the integration of parts of the hospital are discussed within the context of an open-systems conceptual model of hospital organization.