Spray forming

About: Spray forming is a research topic. Over the lifetime, 1153 publications have been published within this topic receiving 12869 citations. The topic is also known as: spray casting & spray deposition.

Metal Matrix Composites

Abstract: Metal matrix composites consist of a metal or an alloy as the continuous matrix and a reinforcement that can be particle, short fiber or whisker, or continuous fiber. In this chapter, we first describe important techniques to process metal matrix composites, then we describe the interface region and its characteristics, properties of different metal matrix composites, and finally, we summarize different applications of metal matrix composites.

Mathematical modeling of the isothermal impingement of liquid droplets in spraying processes

Abstract: A mathematical representation has been developed and computed results are presented describing the spreading of droplets impacting onto a solid substrate. Problems of this type are of major practical interest in plasma spraying (PS) and in spray forming (SF) operations. While the present study was confined to the fluid flow aspects of the process, information has been generated on both the final splat dimensions and on the time required to complete the spreading process. Through this treatment, it is possible to relate these quantities (the splat size and the spreading time) to the operating conditions,i.e., droplet size and droplet velocity, and material properties. The theoretical predictions were found to be in good agreement with both Madejski’s asymptotic solution[17] and with available experimental results. For typical SF conditions (droplet sizes in the 100-µm range and droplet velocities in the 100 m/s range), the spreading times were of the order of microseconds,i.e., significantly shorter than the estimated solidification time.

Solidification progress and heat transfer analysis of gas-atomized alloy droplets during spray forming

Abstract: In order to predict gas and droplet velocities, droplet temperature, and fractional solidification with flight distance during spray forming, the Newtonian heat transfer formulation has been coupled with the classical heterogeneous nucleation and the specific solidification process. It has been demonstrated that the thermal profile of the droplet in flight is significantly affected by process parameters such as droplet size, initial gas velocity, undercooling, and superheat. With increasing droplet size or initial gas velocity, the onset and completion of solidification are shifted to greater flight distances and the solidification process also extends over a wider range of flight distances. It has been found that the corresponding solid fractions formed during recalesced, segregated, and eutectic solidifications are linearly related to the degree of undercooling and that those solid fractions are insensitive to droplet size, initial gas velocity and superheat.

Fluid flow, heat transfer, and solidification of molten metal droplets impinging on substrates: Comparison of numerical and experimental results

Abstract: A mathematical representation has been developed, and computed results are presented describing the spreading and solidification of droplets impacting onto a solid substrate. This impingement is of major practical interest in plasma spraying and spray forming operations. Experiments in which molten metal drops were made to impinge onto a substrate were used to test the model. High-speed videography was used to record the spreading process, which typically took a few milliseconds for the experimental conditions employed. A comparison was made of the theoretical predictions with the experimental measurements; these were found to be in very good agreement, suggesting that the theoretical treatment of the model is sound. These calculations permit the prediction of the time and extent of the spreading process, the solidification rate, and the effect of process parameters, such as droplet size, droplet velocity, superheat, and material properties, provided that a value of the thermal contact coefficient is known. The most important finding of the modeling work is that for large droplets (∼5-mm diameter) with low impinging velocities (∼2 m/s), spreading and solidification appear to take place at comparable rates; in contrast, for small (∼100−µm diameter) particles impacting at a high velocity (∼100 m/s), the time scale for spreading appears to be shorter than the time scale for solidification (within the range of parameters of this study.)

Aluminum-Based Cast In Situ Composites: A Review

Abstract: In situ composites are a class of composite materials in which the reinforcement is formed within the matrix by reaction during the processing. In situ method of composite synthesis has been widely followed by researchers because of several advantages over conventional stir casting such as fine particle size, clean interface, and good wettability of the reinforcement with the matrix and homogeneous distribution of the reinforcement compared to other processes. Besides this, in situ processing of composites by casting route is also economical and amenable for large scale production as compared to other methods such as powder metallurgy and spray forming. Commonly used reinforcements for Al and its alloys which can be produced in situ are Al2O3, AlN, TiB2, TiC, ZrB2, and Mg2Si. The aim of this paper is to review the current research and development in aluminum-based in situ composites by casting route.