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Sneha Samal

Publications and source records attributed to Sneha Samal.

2 recordsLinked to original sources

Mechanical-microstructural correlation on SPS-fabricated NiTi alloy

Mechanical properties and dynamical mechanical analysis were performed on compact Spark Plasma Sinter samples. It has been observed that the sample with less porosity reflects the behavior of superelasticity response. Other samples show failure during first cycles that may be due to porosity. Compaction of metallic powder is one of the standard procedures in the field of powder metallurgy for the fabrication of bulk material. Consolidation of the sample as a function of sintering temperature plays a crucial role in the final compaction mechanism. However, the evolution of compaction, microstructure, phase transformation and mechanical properties as a function of sintering temperature is hardly disclosed. In this work, a correlation has been established between mechanical and microstructural properties of compact samples. The maximum compactness and the corresponding microstructure, porosity, texture, phase transformation, grain size, hardness, mechanical properties of compact samples were discussed. The research establishes mechanical properties-structure correlations for compaction of NiTi alloy in advanced engineering applications.

cond-mat.mtrl-sci

HVAF Spraying of NiTi Coatings: Microstructure, Phase Transformation and Shape Memory Behavior

Depositing various coatings on surface of engineering components with the aim to improve their performance concerning wear, corrosion, friction and thermal protection is already a standard practice. Depositing metallic NiTi shape memory alloy coatings may be a viable alternative for hard ceramic coatings. NiTi coatings offer additional benefits originating from unique functional thermomechanical properties. However, fabrication of thick NiTi coatings turned out to be difficult. Standard electroplating and laser cladding methods are not suitable for NiTi the most widely used plasma spray methods tend to produce chemically inhomogeneous coatings that do not transform martensitically, cold sprayed NiTi coatings suffer from poor adhesion to the substrates. In this work we report on first ever successful fabrication of thick NiTi coatings (100-300 um) that display functional thermomechanical properties and simultaneously show very good adherence to the substrate. We used high velocity air fuel thermal spray method to fabricate NiTi coatings deposited on mild steel using four different sets of processing parameters. Chemical composition, porosity, microstructure, phase transformation and functional thermomechanical properties of the NiTi coatings were evaluated. Although the coatings contain inhomogeneous microstructure, voids, oxide particles, high density of dislocation defects and internal stress, they undergo martensitic transformation upon cooling and or mechanical loading. As sprayed NiTi coatings need to be annealed to display functional thermomechanical properties. Despite their limited tensile strength, the coatings displayed thermal actuation in 3 point bending tests and shape memory effects in nanoindentation and scratch tests.

cond-mat.mtrl-sci