Processing, microstructural evolution and strength properties of in-situ magnesium matrix composites containing nano-sized polymer derived SiCNO particles

Abstract

In-situ Mg matrix composites are fabricated by combining both liquid-and solid-state processing routes. Firstly, liquid polymer was injected into the molten Mg at a temperature of 800 o C to initiate pyrolysis. In-situ pyrolysis aids in the conversion of liquid polymer into sub-micron sized SiCNO particles (mean particle size in the range of 0.5-1 m) and Mg 2 Si particles. Most of the polymer derived SiCNO particles were pushed by the solidification front and as a result segregated at the grain boundaries of as-cast composites (mean grain size in range of 50-65 m) during subsequent solidification process. Formation of Mg 2 Si phase could be minimized by © 2017. This manuscript version is made available under the Elsevier user license http://www.elsevier.com/open-access/userlicense/1.0/ 2reducing the pyrolysis temperature from 800 to 700 o C. Single pass friction stir processing (FSP) of these as-cast composites lead to improved homogeneity in the SiCNO particle distribution, particle refinement (mean particle size of about 200-300 nm) and grain refinement (mean grain size in range of 2.5-3.5 m). Mechanical properties (hardness, compressive yield stress, ultimate compressive stress, strain to failure and strain hardening exponent) of the FS processed composites were enhanced significantly as compared to their as-cast counterparts. Strengthening mechanisms and numerical models are being evoked to explain the observed yield strength in these two stage processed composites.

Microstructural evolution and strengthening behavior in in-situ magnesium matrix composites fabricated by solidification processing

“…During in-situ pyrolysis, the chance of forming (Fig 9(d) Table 3 [13]. The properties and parameters which are used for calculating the various strengthening modes are provided in Table. 4 and Table. 5.…”

“…The most common numerical models to predict the yield strength of particulate MMCs are as follows [13,32] strengthening mechanisms which act unevenly throughout the matrix by least-square approximation. Sanaty-Zadeh et al [32] reported that the modified Clyne method can predict the yield strength more precisely than any other methods after comparing the various numerical models for the particulate MMCs.…”

Synthesis of Magnesium Based Nano-composites

“…reactions between principal alloy and the additives [46][47][48][49][50]. The type and number of additives are chosen based on final formulation of the matrix and volume fraction of the reinforcement.…”

“…Chelliah et al [46] synthesized magnesium-polymeric derived ceramic (PDC) silicon carbonitride (SiCNO) nano composite by liquid pyrolysis using stir casting technique. The liquid poly (urea-methyl-vinyl) silazane (PUVMS) was used to formulate magnesium nano-composite.…”

Amorphous SiCNO hollow nanofibers with mesoporous walls

“…To date, PDCs are mainly classified as binary systems (eg, SiC, Si 3 N 4 , and BN), tertiary system (eg, SiCN, SiCO) and quaternary systems (eg, SiBCN, SiBCO, SiAlCO, and SiCNO), which is based on the number of constituent elements or phases in the final ceramic. Among these various PDCs systems, the Si‐based quaternary ones often possess the free carbon, stable Si–C bonds and overall disordered ceramic structure which make them higher in resistance to oxidation and hot corrosion.…”