Amirthalingam Srinivasan

Microstructure, mechanical, in vitro and in vivo behavior of extruded Mg alloys with varying Zn/Gd ratios, Mg‐2Gd‐2Zn‐0.5Zr (Zn/Gd = 1), Mg‐2Gd‐6Zn‐0.5Zr (Zn/Gd = 3), and Mg‐10Gd‐1Zn‐0.5Zr (Zn/Gd = 0.1) were investigated. The results revealed that the major secondary phases such as W (Mg₃Zn₃Gd₂), (Mg,Zn)₃Gd, LPSO (Long period stacking order) and I (Mg₃Zn₆Gd) phase in alloys depended on Zn/Gd ratio. These second phases influenced the mechanical as well as biological characteristics of the alloys. Among studied alloys, Mg‐10Gd‐1Zn‐0.5Zr alloy showed the highest yield strength and tensile strength of 270 (±9.29) and 330 MPa (±15.8), respectively, with a reasonably good elongation of 12% (±2.36). The presence of Gd₂O₃ in the degradation film of Mg‐10Gd‐1Zn‐0.5Zr enhanced the resistance offered by the film, which resulted in its lowest biodegradation, better viability, and cell proliferation under in vitro condition. The short term (subcutaneous implantation in rats for 1 month) in vivo studies showed that the alloy Mg‐10Gd‐1Zn‐0.5Zr degraded at a rate of 0.35 mm/y (±0.02) and did not induce any toxicity to the vital organs.

Hypoeutectic composition of Al-Mg alloy binary system was established as a stabilized composition for production of Al-Mg alloy nano powders for fabrication of solid propellant. Nano powder of hypoeutectic Al-Mg alloy was prepared by high voltage Electrical Wire Explosion Process (EEW) under inert Argon and Helium gas environment with chamber pressure of 25 kPa and 50 kPa. The thin wires for explosion were prepared by Electrical Discharge Machining (EDM) process from Al-Mg alloy cast. XRD analysis of powder produced and alloy cast was performed to compare the phases present. Scanning Electron Microscope (SEM) images were taken for studying the shape and structure of the nano powder particles and Energy Dispersive Analysis of X-rays (EDX) was performed for affirming elemental composition of alloy powder. Morphological characteristics of nano powders were analyzed by Transmission Electron Microscope (TEM) images and the particle diameter was found ranging from10 nm to 90 nm. Highly magnified TEM images were obtained to analyze the formation of various phases in the powder. Thermo-Gravimetric Analysis and Differential Scanning Calorimetry (TGA-DSC) measurements were made to substantiate the low melting nature of Al-Mg alloys predicted by Al-Mg binary phase diagram with an offset temperature of melting 460 °C, which is much closer to the eutectic melting point (450 °C) of Al-Mg binary metal alloy. With the improved ductility of hypoeutectic alloys enabling better machinability to produce thin wires than eutectic composition, the results suggests hypoeutectic nano powders can be used as replacement for nano aluminium as energetic element in solid propellants