Using heat treatment effects and EBSD analysis to tailor microstructure of hybrid Mg nanocomposite for enhanced overall mechanical response

Abstract

In this study, a detailed investigation on the effect of heat treatment on the microstructural characteristics, texture evolution and mechanical properties of Mg–(5·6Ti+2·5B4C)BM hybrid nanocomposite is presented. Optimised heat treatment parameters, namely, heat treatment temperature and heat treatment time, were first identified through grain size and microhardness measurements. Initially, heat treatment of composites was conducted at temperature range between 100 and 300°C for 1 h. Based on optical microscopic analysis and microhardness measurements, it was evident that significant grain growth and reduction in microhardness occurred for temperatures >200°C. The cutoff temperature that caused significant grain growth/matrix softening was thus identified. Second, at constant temperature (200°C), the effect of variation of heat treatment time was carried out (ranging between 1 and 5 h) so as to identify the range wherein increase in average grain size and reduction in microhardness occurred. Furthering the study, the effect of optimised heat treatment parameters (200°C, 5 h) on the microstructural texture evolution and hence, on the tensile and compressive properties of the Mg–(5·6Ti+2·5B4C)BM hybrid nanocomposite was carried out. From electron backscattered diffraction (EBSD) analysis, it was identified that the optimised heat treatment resulted in recrystallisation and residual stress relaxation, as evident from the presence of ∼87 strain free grains, when compared to that observed in the non-heat treated/as extruded condition (i.e. 2·2 times greater than in the as extruded condition). For the heat treated composite, under both tensile and compressive loads, a significant improvement in fracture strain values (∼60 increase) was observed when compared to that of the non-heat treated counterpart, with ∼20 reduction in yield strength. Based on structure–property correlation, the change in mechanical characteristics is identified to be due to: (1) the presence of less stressed matrix/reinforcement interface due to the relief of residual stresses and (2) texture weakening due to matrix recrystallisation effects, both arising due to heat treatment.

Nano-AlN particle reinforced Mg composites: Microstructural and mechanical properties

“…Similar observations are reported in our recent studies on nano-particle reinforced Mg composites and further studies are in process to comprehensively understand the deformation behaviour in detail. 17,28 The fractographic evidences (Fig. 5) of pure Mg and its nanocomposites under tensile loading also confirm to the results of above observations on the tensile property measurements (Fig.…”

“…11 Further, the results of X-ray analysis are significant to comprehend the role of nanoscale AlN particulates on the crystallographic texture change and the mechanical property improvement. 17,28,31 From the X-ray diffracto-grams, it can be clearly seen that the developed Mg/AlN nanocomposites exhibit dominant basal texture with basal planes alignment parallel to the extrusion direction (max peak observed at 2h532u along the cross-section and 2h534u along the longitudinal section). The development of basal extrusion texture during thermomechanical processing is similar to the observations reported by various researchers in the open literature.…”

“…12 Further, it also clearly states that the mechanical properties enhancement in Mg-MMNCs by nanoscale reinforcement addition primarily depends on the efficient dispersion strengthening effects and non-basal cross slip activation as identified by the change in fracture mode and the reduction in tensile compression yield asymmetry. 10,12,17 The existing literature also suggests that the ceramic particles such as SiC, Al 2 O 3 , SiO 2 and Y 2 O 3 have been extensively used as nanoscale reinforcement in Mg and their beneficial role in improving the mechanical properties of Mg are well documented. However, research works on nanoscale nitride reinforcements such as AlN, BN, Si 3 N 4 and TiN are relatively meagre in the available literature.…”

Synthesis and properties of light weight magnesium–cenosphere composite

“…The significant increase in 0.2% compressive yield strength and ultimate compressive strength of composite foams can primarily be attributed to the presence of reasonably well distributed harder cenosphere particles and secondary phases, load transfer from matrix to reinforcement/second phases, dislocation generation due to elastic modulus mismatch and coefficient of thermal expansion mismatch between the matrix and reinforcement/second phases, and Orowan strengthening mechanism. 8,23–25 It is noted that the total failure strain was increased from 16% to 22, 22.5 and 23% when the additional amount increased from 5 to 10 and 15 wt-%. This is mainly due to the ability of cenosphere particles in resisting the compression force as cenosphere particles themselves exhibit very high compressive strength.…”

Effect of fabrication parameters on carbon fibre reinforced magnesium matrix composite components

“…In this regard, owing to the poor strength and Young's modulus of magnesium alloys at room temperature, to realise the application potential of magnesium alloys, further improvement in the mechanical properties could be achieved by reinforcement. [1][2][3] Carbon fibre reinforced magnesium matrix composites (C f /Mg) exhibited many advantages over the magnesium alloys including high specific strength and specific stiffness, low thermal expansion coefficient and satisfying secondary processing performance, which resulted in good application prospects in aerospace system. [4][5][6] Then, the C f /Mg composites have become an alternative material for the aluminium-magnesium alloy due to the need for lightweight materials.…”