Synthesis and property evaluation of aluminum cr3c2 surface composites prepared via friction stir processing

Abstract

Friction Stir Processing (FSP), a surface modification method evolved from Friction Stir Welding is used in this research to fabricate an Aluminum Surface Composites. FSP is a semi-solid technique, where the temperature of the process is well below than the melting point of the matrix alloy and thereby reducing the chances for the formation of detrimental phases. The FSP tool imposes severe plastic deformation to the matrix material due to its stirring action leading to the micro structural modification of the base metal along with the homogenous dispersion of the ceramic particles. Most commonly used techniques for producing surface composites by FSP are (a) using groove (b) using drilled holes (c) using cover plate. In case of grooving method, first step a groove with known dimension will be machined on the surface of the plate and then the groove is packed with ceramic particles. Next step is to close the groove with a pin less tool to avoid spilling of reinforcement particles during FSP. Finally a tool consisting of pin was used to close the groove. In the current study Aluminum alloy of grade ADC-12 was considered as the matrix metal and Chromium Carbide of varying volume fraction was dispersed onto the surface of ADC-12 through FSP using groove technique. A detailed analysis of the micro structural and mechanical characterization was carried over on the thus developed surface composites. Micro structural characterization of developed surface composites through an optical microscope depicted a reduction in grain size as a function of the plastic deformation created by the vigorous rotating action and load provided by the FSP tool. Up to 18 vol.% of Cr3C2 particle addition to ADC12 alloy were found to be dispersed homogenously on the surface. Further addition of Cr3C2 particles lead to agglomeration in ADC 12 alloy. SEM observation exposed proper bonding between the matrix and ceramic particles. XRD analysis confirms the confirm the presence of added Cr3C2 particles in ADC12 alloy matrix and no other compounds were observed. EBSD analysis confirms that the addition of Cr3C2 particles to ADC12 alloy significantly reduces the matrix grain size from 50 µm to 18 µm. Micro hardness analysis of the developed specimens depicted an enhanced hardness value and it was also accounted from the studies that increase in vol. % of Cr3C2 leads to an increase in the hardness of developed surface composites. Micro hardness of the base metal is found to be 98 HV. At higher rotational speed of 1100 rpm and lower traverse speed of 30 mm/s the hardness of the ADC12/Cr3C2 surface composite is increased to 118.24 HV, and the ultimate tensile strength of the composite material is increase to 330 Mpa from 220 Mpa at 18 Vol. % .UTS was found to increase with an increase in vol. % of reinforcement up to 18 vol. % and further addition of Cr3C2 was found to reduce the UTS and % of elongation. Compared to the base alloy, the developed composites exhibited an improved wear resistance. Increase in vol % of reinforcement lead to increase in wear resistance of the composites up to an addition of 18 vol.% of reinforcement. Further addition of reinforcement was found to decrease the wear resistance of the surface composites. Worn out surfaces of the ADC 12 alloy and surface composites showed adhesive and abrasive are the major wear mechanisms respectively. Compared to ADC12 alloy, developed surface composites exhibits excellent high temperature wear resistance. Mild wear, oxidative wear, mechanical mixing layer formation, thermal softening, plastic deformation and particle pull out are the wear mechanisms identified from the high temperature worn surface. From the corrosion studies it was observed that the FSPed ADC12/ Cr3C2 composites exhibits good corrosion resistance. newline