Papers by Author: Raja K. Mishra

Abstract: Compression tests were employed to characterize the DSA behaviour of Mg-Ce alloys. Samples were taken from cast billets and extruded bars of Mg-0.5 wt.% Ce. The DSA behavior was examined at temperatures from 150°C to 400°C at strain rates of 0.001/s to 1.5/s. A rate equation was fitted to the experimental results, which is employed to predict whether or not DSA will occur at the strain rates and temperatures involved in the formation of the RE texture component during extrusion.

Abstract: This paper summarizes the development of new cast and wrought magnesium alloys using computational thermodynamics tools and experimental approach. The Mg-Al-Ca alloys show excellent creep resistance due to the formation of high-temperature (Mg,Al)₂Ca phase. The Mg-Al-Sn alloys are designed for mechanical properties and corrosion resistance through the optimization of Mg₁₇Al₁₂ and Mg₂Sn phases in the microstructure. In the Mg-Zn-Ce system, Zn provides strength through solid solution strengthening while Ce increases the ductility via improved texture. Mg-Nd-Zn is a heat-treatable alloy system based on the precipitation hardening of Mg₁₂Nd phase.

Abstract: Microstructure Sensitive Design (MSD) offers a rigorous mathematical framework for representing the relevant statistical details of the material microstructure for a given design problem, and for developing quantitative invertible relationships between these microstructure representations and the macroscale properties of interest. The methodology makes extensive use of Fourier representations of the distribution functions representing the material internal structure and existing homogenization theories. In this paper, we describe the application of the MSD framework to fcc polycrystals with a specific focus on the crystallographic texture as the microstructure design variable. The advantages of the MSD approach are demonstrated through a number of elastic-plastic property closures for cubic metals.

Abstract: Predictions of chromium additions to aluminum alloys to stabilize the deformation debris products were examined. Additions of 0.22 wt. % Cr to AA6063 extrusion alloys manifested enhanced formability under bending and precision-strain-rate-sensitivity tensile testing indicated that the stacking fault energy was reduced. The debris products were more resistant to dynamic recovery resulting in enhanced ductility at 27 °C and the solute-drag effect of Mg was dramatically manifested in the Haasen plot.