Abstract
This study investigates the effects of nano-B4C addition and isothermal heat treatment on the microstructure and mechanical properties of Mg-(5.6Ti+3Al) composite developed through the disintegrated melt deposition method followed by hot extrusion. The developed Mg composites were characterized for their microstructural and mechanical properties in the as-extruded and heat treated conditions. Microstructural studies reveal no significant changes to the pre-existing Al 3 Ti intermetallic phases and the average grain size, due to nano-B4C addition. In the as-extruded condition, mechanical properties measurements showed large improvement in fracture strain without significant changes in strength properties due to nano-B 4 C addition. The best combination of strength and ductility observed in Mg-(5.6Ti+3Al)-2.5B 4 C composite was attributed to combined presence of nano-B4C particulates and Al3Ti intermetallics. In the isothermal heat-treated condition (200oC for 5 hours), all the developed Mg composites exhibit significant enhancement in ductility with marginal reduction in strength due to the stress relaxation at matrix-reinforcement interface.
Highlights
Magnesium (Mg) materials with low density (1.74 g/cc) exhibit tremendous application potential in weight critical applications such as in automobile and aerospace sectors
The Ti and Al particulates were ball milled for 2 hours to form (Ti+Al3Ti) composite powder and the resulting ball milled mixture was used as composite reinforcement in Mg matrix
While the composites display refined microstructure when compared to pure Mg [9], no significant changes in the average grain size of Mg composites were observed after nanoB4C addition (Table 1)
Summary
Magnesium (Mg) materials with low density (1.74 g/cc) exhibit tremendous application potential in weight critical applications such as in automobile and aerospace sectors. The mechanical characteristics such as poor elastic modulus and low absolute strength (especially at high temperature) restrict its utilization in critical engineering applications [1,2,3,4] To overcome these limitations, high strength and high modulus ceramic reinforcements such as Al2O3, SiC etc. In addition to the above mentioned conventional ceramic reinforcements, hard, high modulus and high strength intermetallics are being introduced into Mg matrix as reinforcements and these intermetallic reinforcements were prepared either in-situ or through external processing [68] In this regard, our recent work on the development of Mg(5.6Ti+3Al) composite containing (Ti+Al3Ti) phases confirms the possibility of utilizing the externally processed intermetallics as a potential reinforcement to develop new Mg-composites [9]. The current research work is aimed at improving the mechanical response, in particular, the ductility of the Mg-(5.6Ti+3Al) composite
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