Correlation of reactant particle size on residual stresses of nanostructured NiAl generated by self-propagating high-tem
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Michelle L. Pantoya Department of Mechanical Engineering, Texas Tech University, Lubbock, Texas 79409-1021
Karthik Rajamani Oil and Gas Service, Houston, Texas 77057
Simon M. Hsiang Edward P. Fitts Department of Industrial and Systems Engineering, North Carolina State University, Raleigh, North Carolina 27695-7906 (Received 5 October 2008; accepted 6 February 2009)
This investigation analyzed the effect of reactant particle size on the stress development characteristics of NiAl synthesized through self-propagating high temperature synthesis. Four sample combinations of NiAl were synthesized based on initial particle diameters of the reactants: (i) 10 mm Al and 10 mm Ni (S1), (ii) 10 mm Al and 100 nm Ni (S2), (iii) 50 nm Al and 10 mm Ni (S3), and (iv) 50 nm Al and 100 nm Ni (S4). Characterization of NiAl was performed by parallel comparison of the distribution of residual stresses of the samples prior to and after the reaction. Residual stresses were quantified using x-ray diffraction. Upon characterization it was found that combinations S1, S2, and S3 exhibited tensile residual stresses, while combination S4 exhibited compressive residual stresses. Statistical analysis confirmed that self-propagating high temperature synthesis products derived from nanoparticle reactant sizes exhibited compressive residual stresses offering improved fatigue resistance in composite production.
I. INTRODUCTION A. Motivation
Combustion synthesis is an established technique for synthesizing intermetallic alloys, which can be difficult to manufacture using traditional and advanced manufacturing processes. Traditional synthesis processes include conventional melting and casting, powder metallurgy, mechanical alloying, vacuum arc remelting, and electron beam melting, to name a few.1 A disadvantage of these processes is that they require complex equipment besides being time- and energy-intensive. Advanced synthesis processes include sol gel, hydrothermal synthesis, and chemical vapor deposition. In general, the combustion synthesis method is described as a self-propagating exothermic reaction that transforms discreetly distinct reactants into a product alloy. In essence, the method is based on the availability of a heterogeneous and sufficiently exothermic chemical reaction to produce (after ignition with an external energy pulse) a reaction front, steadily propagating as a thermal and chemical wave through the a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2009.0240 J. Mater. Res., Vol. 24, No. 6, Jun 2009
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heterogeneous mixture of reactants.2 In the self-propagating high temperature synthesis (SHS) reaction, the pellet is heated locally to stimulate ignition. Once ignition is achieved, the external energy source is removed and the reactants are consumed by the self-propagating combustion reaction. As the reaction propagates, high heating rates can be achieved such that the product material is free from volatile contaminants and impur
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