Making Federal Financial Data More Reliable With Emerging Tech

Symposium PresentationApproved for public release; distribution is unlimited

Making Federal Financial Data More Reliable With Emerging Tech

Excerpt from the Proceedings of the Nineteenth Annual Acquisition Research SymposiumFederal agencies are stewards of billions in taxpayer funds. Given the scale of federal financial transactions, maintaining reliable, high-quality financial data can be challenging. The use of emerging technologies such as robotic process automation (RPA) and natural language processing can reduce manual work for agency employees and improve the consistency of financial data. These technologies are key to success on financial audits and maintaining public confidence in the reliability of procurement and nonprocurement financial information.Approved for public release; distribution is unlimited

Effect of PWHT on the Microstructure and Mechanical Properties of Friction Stir Welded DP780 Steel

In the present study, the effect of post-weld heat treatment (PWHT) on the microstructure and mechanical properties of friction stir welded (FSW) DP780 steel sheets was investigated. FSW was carried out at a constant tool rotation speed of 400 rpm and different welding speeds (200 mm/min and 400 min/min). A defect free weld was witnessed for both of the welding conditions. The mutual effect of severe plastic deformation and frictional heat generation by pin rotation during the FSW process resulted in grain refinement due to dynamic recrystallization in the stir zone (SZ) and thermo-mechanically affected zone (TMAZ). Lower tensile elongation and higher yield and ultimate tensile strengths were recorded for welded-samples as compared to the base material (BM) DP780 steel. The joints were subsequently annealed at various temperatures at 450–650 °C for 1 h. At higher annealing temperature, the work hardening rate of joints gradually decreased and subsequently failed in the softened heat-affected zone (HAZ) during the uniaxial tensile test. Reduction in yield strength and tensile strength was found in all PWHT conditions, though improvement in elongation was achieved by annealing at 550 °C. The digital image correlation analysis showed that an inhomogeneous strain distribution occurred in the FSWed samples, and the strain was particularly highly localized in the advancing side of interface zone. The nanoindentation measurements covering the FSWed joint were consistent with an increase of the annealing temperature. The various grains size in the BM, TMAZ, and SZ is the main factor monitoring the hardness distribution in these zones and the observed discrepancies in mechanical properties

Investigating the Microstructure, Crystallographic Texture and Mechanical Behavior of Hot-Rolled Pure Mg and Mg-2Al-1Zn-1Ca Alloy

In this study, the microstructure, crystallographic texture and the mechanical performance of hot-rolled pure Mg and Mg-2Al-1Zn-1Ca (herein inferred as AZX211) were thoroughly investigated. The results showed that the designed AZX211 alloy exhibited an exceptional strength/ductility synergy where an almost 40% increase in ductility was received for AZX211. The microstructural characterization revealed the grain refinement in the AZX211, where the grain size was reduced by more than 50% (24.5 µm, 10 µm for the pure Mg and the AZX211, respectively). Moreover, a discernible number of precipitates were dispersed in the AZX211, which were confirmed to be (Mg, Al)2Ca. The pure Mg showed a conventional strong basal texture while a significantly weakened split basal texture was received for the AZX211. The fraction of basal-oriented grains was 21% for the pure Mg and 5% for the AZX211. The significant texture weakening for the AZX211 can be attributed to the precipitation and co-segregation that triggered the preferential evolution of the non-basal grains while impeding the growth of the basal grains. This was also confirmed by the crystal orientation and the pseudo-rocking curves. The higher ductility of the AZX211 was explained based on the texture softening and Schmid factor for the basal and non-basal slip systems

A Further Improvement in the Room-Temperature Formability of Magnesium Alloy Sheets by Pre-Stretching

Pre-stretching experiments were carried out on AZ31–0.5Ca magnesium alloy to alter the microstructure and texture for enhancing room-temperature formability. Compared to as-received alloy, the formability of a 5%-stretched sample was improved by 15%. This was attributed to enhanced strain hardening capability related to the weakening of basal texture and less homogeneous microstructure. In addition, in-grain misorientation axis analysis performed on the samples (as-received and stretched) also confirmed the higher activity of the non-basal slip systems in the 5%-stretched sample

Investigating the Microstructure, Crystallographic Texture and Mechanical Behavior of Hot-Rolled Pure Mg and Mg-2Al-1Zn-1Ca Alloy

In this study, the microstructure, crystallographic texture and the mechanical performance of hot-rolled pure Mg and Mg-2Al-1Zn-1Ca (herein inferred as AZX211) were thoroughly investigated. The results showed that the designed AZX211 alloy exhibited an exceptional strength/ductility synergy where an almost 40% increase in ductility was received for AZX211. The microstructural characterization revealed the grain refinement in the AZX211, where the grain size was reduced by more than 50% (24.5 µm, 10 µm for the pure Mg and the AZX211, respectively). Moreover, a discernible number of precipitates were dispersed in the AZX211, which were confirmed to be (Mg, Al)2Ca. The pure Mg showed a conventional strong basal texture while a significantly weakened split basal texture was received for the AZX211. The fraction of basal-oriented grains was 21% for the pure Mg and 5% for the AZX211. The significant texture weakening for the AZX211 can be attributed to the precipitation and co-segregation that triggered the preferential evolution of the non-basal grains while impeding the growth of the basal grains. This was also confirmed by the crystal orientation and the pseudo-rocking curves. The higher ductility of the AZX211 was explained based on the texture softening and Schmid factor for the basal and non-basal slip systems

Microstructure Features and Superplasticity of Extruded, Rolled and SPD-Processed Magnesium Alloys: A Short Review

In this study, an overview of microstructure features such as grain size, grain structure, texture and its impact on strain rate sensitivity, strain hardening index, activation energy and thermal stability for achieving superplasticity of Mg alloys are presented. The deformation behavior under different strain rates and temperatures was also elaborated. For high elongation to fracture grain boundary sliding, grain boundary diffusion is the dominant deformation mechanism. In contrast, for low-temperature and high strain rate superplasticity, grain boundary sliding and solute drag creep mechanism or viscous glide dislocation followed by GBS are the dominant deformations. In addition, the results of different studies were compared, and optimal strain rate and temperature were diagnosed for achieving excellent high strain rate superplasticity

Designing highly ductile magnesium alloys: Current status and future challenges

10.1080/10408436.2021.1947185Critical Reviews in Solid State and Materials Sciences472194-28

Synergetic improvement in strength and ductility of AZX211 Mg alloy facilitated by {10–12}-{01–12} twin-twin interactions during pre-stretching at cryogenic temperature

In the pursuit of enhancing the mechanical properties of magnesium alloys, particularly AZX211, which is renowned for its lightweight characteristics but plagued by low ductility and strength, this study explores the effects of cryogenic pre-stretching at −170 °C. The research reveals that cryogenic pre-stretching triggers the formation of a complex twinning network comprising thin tension twin {10–12} lamellas and multiple twin variants, significantly improving both strength and ductility in the material. The enhanced ductility is attributed to the activation of the prismatic slip system due to texture reorientation, as confirmed by Schmid factor criteria and in-grain misorientation axes (IGMA) analysis

Probabilistic Fatigue Life Prediction of Dissimilar Material Weld Using Accelerated Life Method and Neural Network Approach

Welding alloy 617 with other metals and alloys has been receiving significant attention in the last few years. It is considered to be the benchmark for the development of economical hybrid structures to be used in different engineering applications. The differences in the physical and metallurgical properties of dissimilar materials to be welded usually result in weaker structures. Fatigue failure is one of the most common failure modes of dissimilar material welded structures. In this study, fatigue life prediction of dissimilar material weld was evaluated by the accelerated life method and artificial neural network approach (ANN). The accelerated life testing approach was evaluated for different distributions. Weibull distribution was the most appropriate distribution that fits the fatigue data very well. Acceleration of fatigue life test data was attained with 95% reliability for Weibull distribution. The probability plot verified that accelerating variables at each level were appropriate. Experimental test data and predicted fatigue life were in good agreement with each other. Two training algorithms, Bayesian regularization (BR) and Levenberg–Marquardt (LM), were employed for training ANN. The Bayesian regularization training algorithm exhibited a better performance than the Levenberg–Marquardt algorithm. The results confirmed that the assessment methods are effective for lifetime prediction of dissimilar material welded joints