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IIT Kharagpur
Abstract
In this study the direct metal laser sintering (DMLS) process was successfully applied to develop the aluminium based metal matrix composites (Al-MMCs) with both ex- situ and in-situ reinforcements. Initially, SiC particulate (SiCp) reinforced Al-MMC was successfully produced using pulsed Nd:YAG laser. Taguchi design of experiments was applied to obtain the optimal parameters for the responses (density, porosity and microhardness). Porosity and density are more dependent on hatching distance than layer thickness. The percentage of SiCp has greater influence on micro- hardness than pulse energy. Density and porosity remain almost constant with the variation of SiCp size within the range of study. 300 mesh of SiCp gave better results.
Addition of SiCp beyond 15 volume % does not improve density and porosity.
Although microhardness improves with increase in volume fraction of the reinforcement but it is found that crack density changes notably after 15 volume %.
The specific wear rate increases with the decrease in reinforcement size for a given volume percentage of SiCp. There is no enhancement in wear resistance after 20 vol.
%. SiCp. The ex-situ SiCp reinforced Al-MMC was successfully fabricated also with the help of a continuous wave Yb-fibre laser. It was found that with increase in laser power density and microhardness increase whereas specific wear rate and porosity decrease. The density, porosity and microhardness decrease and specific wear rate increases with increase in layer thickness and hatching distance. The decrease in scan speed improves the above mentioned properties.
In-situ Al2O3, TiC and TiB2 reinforced Al-MMC was successfully synthesized by combined SHS and DMLS process using continuous wave Yb-fibre laser. Taguchi method was successfully applied to obtain the optimal parameters. Hatching distance was found out to be the major influencing parameter on porosity and density. The composition of powder material is the key parameter to improve the microhardness and specific wear rate. The SEM and XRD analysis shows the microstructure and formation of intermetallic compounds. The knowledge and information thus generated
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IIT Kharagpur
are not only of academic importance but also of relevance to actual users and industries involved in the manufacture of Al based MMC.
Keywords: Laser; DMLS; Al-MMC; optimisation, density; porosity; microhardness;
specific wear rate; SEM.
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