Evaluation of Mechanical Properties and Microstructure for Laser Deposition Process and Welding Process

Laser Aided Manufacturing Process (LAMP) can be applied to repair steel die/molds which are currently repaired using traditional welding process in industry. In order to fully understand the advantages of laser deposition repair process over traditional welded-repair process, the mechanical properties such as tensile strength and hardness of H13 tool steel samples produced by these two processes were investigated. The microstructure and fracture surface of the samples were analyzed using optical microscope and SEM (Scanning Electron Microscope). Moreover, depositions on substrates with different shapes were studied to evaluate the performance of LAMP on damaged parts with complicated geometric shape.Mechanical Engineerin

Numerical Simulation and Prediction of Dilution during Laser Deposition

The laser additive manufacturing technique of laser deposition allows quick fabrication of fully-dense metallic components directly from Computer Aided Design (CAD) solid models. The applications of laser deposition include rapid prototyping, rapid tooling and part refurbishment. The development of an accurate predictive model for laser deposition is extremely complicated due to the multitude of process parameters and materials properties involved. In this work, a heat transfer and fluid flow model is developed. The model is used to predict dilution under varying process parameters for deposits of Ti-6Al-4V. Experimental validation of the predicted dilution is presented. The laser used is a direct diode lase

Numerical Simulation of the Evolution of Solidification Microstructure in Laser Deposition

A predictive model is developed to simulate the evolution of the solidification microstructure during the laser deposition process. The microstructure model is coupled with a comprehensive macroscopic thermodynamic model. This model simulates dendritic grain structures and morphological evolution in solidification. Based on the cellular automata approach, this microstructure model takes into account the heterogeneous nucleation both within the melt pool and at the substrate/melt interface, the growth kinetics, and preferential growth directions of dendrites. Both diffusion and convection effects are included. This model enables prediction and visualization of grain structures during and after the deposition process. This model is applied to Ti-6Al-4V

Conventional and Molecular Breeding Approaches for Biofortification of Pearl Millet

Pearl millet [Pennisetum glaucum (L.) R. Br.] is an essential diet of more than 90 million people in the semi-arid tropics of the world where droughts and low fertility of soils cause frequent failures of other crops. It is an important nutri-rich grain cereal in the drier regions of the world grown on 26 mha by millions of farmers (IFAD 1999; Yadav and Rai 2013). This makes pearl millet the sixth most important crop in the world and fourth most important food crop of the India, next to rice, wheat, and maize with annual cultivation over an area of ~8 mha. Pearl millet is also primary food crop in sub-Saharan Africa and is grown on 15 mha (Yadav and Rai 2013). The significant increase in productivity of pearl millet in India is attributed to development and adoption of hybrids of early to medium duration maturity. More than 120 diverse hybrids/varieties have been released till date for various production environments. The heterosis breeding and improved crop management technologies increased productivity substantially achieving higher increased production of 9.80 mt in 2016–2017 from 2.60 mt in 1950–1951 in spite of declined of area under the crop by 20–30% over last two decades (Yadav et al. 2012)

Friction stir processing for local modification of aluminum components

Friction stir processing was used for local modification of powder metallurgy alloys and to prepare a surface composite for wear and friction applications. Sintered Al 2014 compacts were processed to two different conditions; stirred and stirred plus heat treated to T6. Al 6061 compacts were processed to three different conditions, green compacts were stirred, sintered compacts were stirred, and sintered compacts were stirred and then treated to T6. The two alloys in the different conditions were tested for mechanical properties. In all cases the materials in the stirred volume was superior to the unstirred material. Furthermore heat treating to the T6 condition enhanced all the measured properties in the stirred volume with the only exception being ductility --Abstract, page iv

Local Surface Modification of P/M Parts without Furnace Treatments

The design of a process to produce a P/M part is driven by shape control, dimensional control, cost and finally properties. Significant compromises are made in order to balance these attributes. Secondary operations allow some separation of these attributes allowing more design flexibility. A new application of friction stir processing produces surface modification with dramatic improvements in properties and good control of shape and dimensions. As all energy used is electrical from mechanical motors and generated in the part to be modified, it is highly efficient with low energy costs. A number of P/M materials have been modified with aluminum, steel and an aluminum matrix composite given as examples. Friction stir processing is capable of lower part costs or producing higher performance parts

Furnaceless Sintering of P/M Materials through Friction Stirring

Processes that combine thermal processing and mechanical processing, such as hot extrusion and hot pressing, are well known to be capable of fully densifying particulate materials. This is particularly useful for prealloyed materials where cold compaction would be difficult. A new application of friction stir processing has been developed to provide thermomechanical processing of particulate materials leading to densification of green materials. As the heat is generated solely by the mechanical action of the tool, no furnace is needed and the energy costs are proportionally lower. Temperature is controlled by machine parameters and the material. Materials range from low sintering temperature materials such as aluminum to steels. Since diffusion is enhanced by the mechanical work, inhomogeneous materials are homogenized. Mechanical properties are enhanced as would be expected from the high density and chemical homogeneity. Examples of materials processed in this manner will be given and the mechanisms for densification discussed

Local Modification of P/M Parts to Fully Densify and Enhance Properties

P/M part design is similar to casting in that different properties can be achieved at different locations on a part. Most of this is accomplished through secondary processes, such as repressing or infiltration. While partially successful in modifying properties, it is difficult to alter the local microstructure beyond modifying the pores. A near net-shape thermomechanical process, Friction Stir Processing has been applied to press and sintered P/M parts to both eliminate porosity and homogenize and refine the microstructure. Exceptional improvements in local properties can be made, including increasing hardness, ductility, etc., while decreasing permeability and increasing the response to heat treatment. The action of the friction stir processing is to stir the solid material like cookie dough. There is a local short temperature rise to the hot working range followed by a rapid self quench. Examples of several different materials will be described along with property improvements

Evaluating LDL-C control in Indian acute coronary syndrome (ACS) patients- A retrospective real-world study LDL-C control in ACS

Background: Low-density lipoprotein-cholesterol (LDL-C) is an independent risk factor for atherosclerotic cardiovascular disease (ASCVD) progression. Although lipid lowering therapies remain the cornerstone of secondary ACSVD prevention, there exists residual dyslipidemia. The current study aimed to evaluate the real-world experience related to the treatment patterns and LDL-C control in Indian Acute Coronary Syndrome (ACS) patients. Methods: This was a real-world, descriptive, retrospective, observational, and multicentric study conducted across India. The data was collected for 1 year following the ACS event. The change in the levels of LDL-C from the baseline to the follow-up visits and the control of LDL-C, the change in lipid profile, lipoprotein levels, treatment patterns for lipid-lowering, and tolerability of existing treatments were evaluated. Results: Overall, 575 patients were included from 11 centers across India. The mean age of the patients was 52.92 years, with male predominance (76.35%). Although there was a significant reduction in the mean levels of LDL-C from the baseline [(122.64 ± 42.01 mg/dl to 74.41 ± 26.45 mg/dl (p < 0.001)], it was observed that despite high-intensity statin therapy, only 20.87% patients managed to achieve target LDL-C of <55 mg/dL and 55.65% were unable to reach LDL-C levels of <70 mg/dl one year after the event. Six patients reported adverse events without treatment discontinuation. Conclusion: The majority of the patients received high-intensity statins and did not attain target LDL-C levels, suggesting LDL-C control after an ACS event requires management with novel therapies having better efficacy as recommended by international and national guidelines