Abstract: Aluminum based alloys equally exhibit low density and good mechanical properties. Reinforcement of such alloys with Mg2Si can lead to additional improvements in the mechanical properties, especially in thermal resistance, together with a reduction in density. Only a low Mg 2Si-content can be reached in aluminium alloys using a common process. A fine distribution and high Mg2Si-content ( 15 mass-% Mg2Si) can be achieved by spray forming. Due to its higher solidification rate the formation of undesired phase morphologies is suppressed by this production technique. Aluminum alloys with Mg2Si-contents of 22-34 mass-% were successfully spray formed and were subsequently extruded and heat treated. Additional alloying with 1.8 mass-% copper leads to a further increase in strength by metastable Al-Cu-phases. The microstructure, density and mechanical properties of these new light-weight aluminum alloys have been investigated. The size of the primary Mg2Si-particles in the alloys was not influenced by extrusion or heat treatment while changes in the other phases were observed. An increase in Mg2Si-content reduces the density to below 2.5 g/cm3 while improving the mechanical properties. During tensile tests at elevated temperatures the material exhibits good thermomechanical resistance. The Mg2Si particle size, obtained by variations in the spray forming prozess, had a significant influence on the mechanical properties. Applications for the new light-weight aluminum alloys can be expected wherever a reduced density together with high hot yield strength would lead to a more compact design in high temperature environments, such as in combustion engines.
Notes: Compilation and indexing terms, Copyright 2011 Elsevier Inc. xD;20084211644975 xD;Low density
Abstract: In Spray Forming, specific enthalpy is a key parameter in the deposition process as it influences the thermal condition of the impinging droplets as well as that of the deposit surface. An empirical model for the distribution of specific enthalpy in the spray cone was developed as an easy to handle alternative to numerical models with which the descriptive partial differential equations are solved numerically. The model results were compared with the experimental data to validate its applicability.
Notes: Bft53 xD;Times Cited:0 xD;Cited References Count:8 xD;Materials Science Forum
Abstract: Porosity in spray-formed materials is an important issue, but the formation of porosity is not completely understood. Many experimental results and some theoretical models have been presented in the past. Nevertheless, the prediction of porosity in a deposit is still not possible today. The paper will give some examples picked from literature, which show some general correlations between process parameters and porosity. These correlations can be helpful to form a basic understanding of the process. Finally it is necessary to know more about the conditions of the droplets and the deposit at the point of impingement. These impacting conditions have to be correlated to the porosity to improve the understanding of the process and to make a prediction possible. Determining the impact conditions is a challenge because usually they are not constant with time and some values are difficult to measure. xD;Our experiments show a strong correlation between the surface temperature of the deposit and the porosity. For IN718 and U720 as-sprayed porosities below 1 vol.% were achieved if the deposit surface temperature is app. 1250 degrees C. The average impact angle weighted by the local particle mass flux is also an important parameter. The probability of low as-sprayed porosity is high if the average weighted impact angle is below 25 degrees but decreases dramatically for higher impact angles.
Notes: Bft53 xD;Times Cited:4 xD;Cited References Count:7 xD;Materials Science Forum
Abstract: Aluminium Alloys with a 22 wt.-% Mg2Si content were spray formed. This alloy features a low density and is therefore a superior material for lightweight applications. The main problem in the spray forming of this type of alloy was the occurrence of high porosities. First process optimizations have been performed to decrease porosity under a certain level, so that it can be closed by an extrusion process.
Notes: Bft53 xD;Times Cited:3 xD;Cited References Count:4 xD;Materials Science Forum
Abstract: Spray forming as a technology to produce near net shape components or preforms for additional forming operations with defined microstructural properties is well known for several alloys and applications. The production of spray formed superalloy rings made of IN718 and U720 for aero engine components in order to reduce production cost is the goal of the current EU-research project. Several spray runs were carried out at University of Bremen to optimize the process parameters regarding a low porosity, low segregation and a high yield. Macro and micro-etchings were prepared to analyze the influence of the parameter variations on before mentioned structural properties. Several optimized rings were used to examine the influence of thermomechanical processing on porosity and microstructure of spray formed superalloy rings. Hot isostatic pressing and forging processes were performed separately as well as in combination in order to obtain the ideal post processing route, which was determined via microstructure analysis. As a result of this project, it became clear that HIPping is an integral part of the post-processing of as-sprayed material, due to the fact that it was not possible to produce as-sprayed material without porosity. The development of micro- and macro structural properties through all these processes and their variations will be shown. Another paper presented here will focus on the final properties and applications of this material.
Abstract: A novel technique, impulse atomization, has been used for spray deposition. This single fluid atomization technique leads to different spray characteristics and impact conditions of the droplets compared to gas atomization technique which is the common technique used for spray deposition. Deposition experiments with a Cu-6Sn alloy were conducted to evaluate the appropriateness of impulse atomization to produce dense material. Based on these experiments, a model has been developed to simulate the thermal history and the local solidification rates of the deposited material. A numerical study shows how different cooling conditions affect the solidification rate of the material. (C) 2004 Elsevier B.V. All rights reserved.
Abstract: Aluminium Alloys with a 22 wt.-% Mg2Si content were spray formed. This alloy features a low density and is therefore a superior material for lightweight applications. The main problem in the spray forming of this type of alloy was the occurrence of high porosities. First process optimizations have been performed to decrease porosity under a certain level, so that it can be closed by an extrusion process.
Notes: Compilation and indexing terms, Copyright 2011 Elsevier Inc. xD;20080511062730 xD;Spray forming xD;Superior material
Abstract: In Spray Forming, specific enthalpy is a key parameter in the deposition process as it influences the thermal condition of the impinging droplets as well as that of the deposit surface. An empirical model for the distribution of specific enthalpy in the spray cone was developed as an easy to handle alternative to numerical models with which the descriptive partial differential equations are solved numerically. The model results were compared with the experimental data to validate its applicability.
Notes: Compilation and indexing terms, Copyright 2011 Elsevier Inc. xD;20080511062726 xD;Enthalpy distribution xD;Specific enthalpy
Abstract: Porosity in spray-formed materials is an important issue, but the formation of porosity is not completely understood. Many experimental results and some theoretical models have been presented in the past. Nevertheless, the prediction of porosity in a deposit is still not possible today. The paper will give some examples picked from literature, which show some general correlations between process parameters and porosity. These correlations can be helpful to form a basic understanding of the process. Finally it is necessary to know more about the conditions of the droplets and the deposit at the point of impingement. These impacting conditions have to be correlated to the porosity to improve the understanding of the process and to make a prediction possible. Determining the impact conditions is a challenge because usually they are not constant with time and some values are difficult to measure. Our experiments show a strong correlation between the surface temperature of the deposit and the porosity. For IN718 and U720 as-sprayed porosities below 1 vol.% were achieved if the deposit surface temperature is app. 1250C The average impact angle weighted by the local particle mass flux is also an important parameter. The probability of low as-sprayed porosity is high if the average weighted impact angle is below 25 but decreases dramatically for higher impact angles.
Notes: Compilation and indexing terms, Copyright 2011 Elsevier Inc. xD;20080511062729 xD;Impact angle xD;Sprayed porosities xD;Surface temperature
