Microstructural Evolution as a Function of Increasing Aluminum Content in Novel Lightweight Cast Irons

Alejandro Obregon,Gurutze Arruebarrena,Ion Quintana,Jose Carlos Garcia,Jon Mikel Sanchez,Iñaki Hurtado,David Eguizabal,Patxi Rodriguez

doi:10.3390/met11101646

Alejandro Obregon, Gurutze Arruebarrena + Show 6 more

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https://doi.org/10.3390/met11101646

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Abstract

In the context of the development of new lightweight materials, Al-alloyed cast irons have a great potential for reducing the weight of the different part of the vehicles in the transport industry. The correlation of the amount of Al and its effect in the microstructure of cast irons is not completely well established as it is affected by many factors such as chemical composition, cooling rate, etc. In this work, four novel lightweight cast irons were developed with different amounts of Al (from 0 wt. % to 15 wt. %). The alloys were manufactured by an easily scalable and affordable gravity casting process in an induction furnace, and casted in a resin-bonded sand mold. The microstructural evolution as a function of increasing Al content by different microstructural characterization techniques was studied. The hardness of the cast irons was measured by the Vickers indentation test and correlated with the previously characterized microstructures. In general, the microstructural evolution shows that the perlite content decrease with the increment of wt. % of Al. The opposite occurs with the ferrite content. In the case of graphite, a slight increment occurs with 2 wt. % of Al, but a great decrease occurs until 15 wt. % of Al. The addition of Al promotes the stabilization of ferrite in the studied alloys. The hardness obtained varied from 235 HV and 363 HV in function of the Al content. The addition of Al increases the hardness of the studied cast irons, but not gradually. The alloy with the highest hardness is the alloy containing 7 wt. % Al, which is correlated with the formation of kappa-carbides and finer perlite.

Highlights

Weight reduction has become an important element to reduce greenhouse gas emissions in the transport industry
Motivated by the above concerns, and because of the great potential that lightweight cast iron to reduce the density and overpass the mechanical properties of traditional cast irons, this study developed four novel Fe-Al-C-Si lightweight gray cast iron alloys
The as-cast microstructures of each alloy subsequently observed by optical microscopy (OM) were correlated with the mass percent of Al in the diagram

Summary

Introduction

Weight reduction has become an important element to reduce greenhouse gas emissions in the transport industry. A great deal of effort is being made in the development of novel materials with improved mechanical and/or physical properties, with light weight as the main goal. The transport industry depends on the development of new lightweight materials to optimize the fuel consumption of the generation of vehicles. With the goal of complying with global vehicle emissions regulations, the research focus is on the development of new materials to replace traditional alloys for reducing energy consumption and, thereby, gas emissions (NOx, CO2 , etc.). New materials should not compromise structural properties, or contribute to significant cost increases. In this way, novel materials such as complex concentrated alloys, medium/high entropy alloys, aluminum-based hybrid composites, etc. Novel materials such as complex concentrated alloys, medium/high entropy alloys, aluminum-based hybrid composites, etc. has been developed in the last years [1,2,3,4,5]

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