Customised Alloy Blends for In-Situ Al339 Alloy Formation Using Anchorless Selective Laser Melting

The additive manufacturing process Selective Laser Melting (SLM) can generate large thermal gradients during the processing of metallic powder; this can in turn lead to increased residual stress formation within a component. Metal anchors or support structures are required to be built during the process and forcibly hold SLM components to a substrate plate and minimise geometric distortion/warpage due to the process induced thermal residual stress. The requirement for support structures can limit the geometric freedom of the SLM process and increase post-processing operations. A novel method known as Anchorless Selective Laser Melting (ASLM) maintains processed material within a stress relieved state throughout the duration of a build. As a result, metal components formed using ASLM do not develop signification residual stresses within the process, thus, the conventional support structures or anchors used are not required to prevent geometric distortion. ASLM locally melts two or more compositionally distinct powdered materials that alloy under the action of the laser, forming into various combinations of hypo/hyper eutectic alloys with a new reduced solidification temperature. This new alloy is maintained in a semi-solid or stress reduced state for a prolonged period during the build with the assistance of elevated powder bed pre-heating. In this paper, custom blends of alloys are designed, manufactured and processed using ASLM. The purpose of this work is to create an Al339 alloy from compositionally distinct powder blends. The in-situ alloying of this material and ASLM processing conditions allowed components to be built in a stress-relieved state, enabling the manufacture of overhanging and unsupported features

AlSi12 In-Situ Alloy Formation and Residual Stress Reduction using Anchorless Selective Laser Melting

Rapid melt pool formation and solidification during the metal powder bed process Selective Laser Melting (SLM) generates large thermal gradients that can in turn lead to increased residual stress formation within a component. Metal anchors or supports are required to be built in-situ and forcibly hold SLM structures in place and minimise geometric distortion/warpage as a result of this thermal residual stress. Anchors are often costly, difficult and time consuming to remove and limit the geometric freedom of this Additive Manufacturing (AM) process. A novel method known as Anchorless Selective Laser Melting (ASLM) maintains processed material within a stress relieved state throughout the duration of a build. As a result metal components formed using ASLM do not require support structures or anchors. ASLM locally melts two or more powdered materials that alloy under the action of the laser and can form into various combinations of eutectic/hypo/hyper eutectic alloys with a new lower solidification temperature. This new alloy is maintained in a semi-solid or stress reduced state throughout the build with the assistance of elevated powder bed pre-heating. In this paper the ASLM methodology is detailed and investigations into processing of a low temperature eutectic Al-Si binary casting alloy is explored. Two types of Al powders were compared; pre-alloyed AlSi12 and elemental mix Al + 12 wt% Si. The study established an understanding of the laser in-situ alloying process and confirmed successful alloy formation within the process. Differential thermal analysis, microscopy and X-Ray diffraction were used to further understand the nature of alloying within the process. Residual stress reduction was observed within ASLM processed elemental Al + Si12 and geometries produced without the requirement for anchors

A Method to Eliminate Anchors/Supports from Directly Laser Melted Metal Powder Bed Processes

Metal powder bed AM processes have a significant drawback in that they require anchors/supports to hold overhanging features down during laser processing. This severely restricts the geometries that the processes can make, adds significant time and cost to production and reduces throughput as parts cannot be easily stacked in the build bed. A method to eliminate the need for these anchors/supports has been invented and will be described. Early parts made without anchors will be shown and next steps for research will be discussed

Investigating a Semi-Solid Processing technique using metal powder bed Additive Manufacturing Processes

The work reported investigates in-situ alloying using a semi-solid processing technique with metal powder bed Additive Manufacturing (AM); in this instance Selective Laser Melting (SLM) and Electron Beam Melting (EBM) were employed. This technique utilised customised powder blends that were processed at elevated temperatures. The selection of processing temperature considered specific alloy solidification ranges. As a result, parts with reduced residual stresses can be produced. In addition, the use of customised powder blends explored the feasibility of developing alloys specific to the process/application, thus increasing available material ranges for AM metal powder bed processes

Benchmarking metal powder bed Additive Manufacturing processes (SLM and EBM) to build flat overhanging geometries without supports

Metal powder Additive Manufacturing (AM) allows complex parts to be build from commercial materials. Several industries such as automotive, aerospace and medical have interests in using these technologies. However in metal powder AM, supports/ anchors are required to be melted in place to avoid process failure due to upward warping of flat overhanging geometries. This leads to additional melting of materials, processing time and thus increasing costs of parts build. A series of experiments were conducted to understand capability of processes such as Selective Laser Melting (SLM) and Electron Beam Melting (EBM) to build flat overhang geometries. In addition, effect of preheating the powder feedstock was also performed

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Not AvailableProductivity of cropland soils, especially in arid and semi - arid tropics of India rigorously declined due to increasing losses of soil organic carbon (SOC) over the past decades. In the present study, we examined a 16 - years long term experiment with continuous mono cropping rainfed groundnut (Arachis hypogaea) to quantify the influence of fertilization and manuring on yield sustainability and C sequestration potential on rainfed Vertisols of Western India. The treatments include, (i) T1 = control; (ii) T2 = 100% recommended dose of fertilizer [RDF - 20:40:40 kg ha−1 of N:P2O5: K2O]; (iii) T3 = integrated nutrient management [INM - 50% RDF + compost 6 Mg ha−1 + biofertilizers (BF)]; (iv) T4 = organic nutrient source [compost 6 Mg ha−1 + vermicompost (VC) 2 Mg ha−1 + castor neem cake (CNC) 250 kg ha−1 + BF + mulching]. Maximum mean groundnut pod yield (1.17 Mg ha−1) was recorded in T2 which was statistically similar to T4 (1.16 Mg ha−1). However, Mann - Kendall test for yield trend suggests the consistency in yield increase under T3 treatment during the last 16 years. The rate of pod yield enhancement was 27 kg ha−1 for every Mg increase in profile SOC stock. The mean SOC concentration (g kg−1) of 1 - m soil depth increased from 4.0 to 5.6 (40%) in T4 over control and the mean SOC sequestration rate was 0.63 Mg C ha−1 yr−1. A minimum of 1.22 Mg C ha−1 yr−1 input was needed to maintain SOC stock at its antecedent level (zero change). We conclude that combined use of chemical fertilizers along with locally available organic resources is essential for enhancing SOC storage while achieving sustainable crop productivity in semi - arid agro - ecosystem.Not Availabl

Influence of 16 years of fertilization and manuring on carbon sequestration and agronomic productivity of groundnut in vertisol of semi-arid tropics of Western India

Productivity of cropland soils, especially in arid and semi-arid tropics of India rigorously declined due to increasing losses of soil organic carbon (SOC) over the past decades. In the present study, we examined a 16-years long term experiment with continuous mono cropping rainfed groundnut (Arachis hypogaea) to quantify the influence of fertilization and manuring on yield sustainability and C sequestration potential on rainfed Vertisols of Western India. The treatments include, i) T1 = control; ii) T2 = 100% recommended dose of fertilizer [RDF-20:40:40 kg ha−1 of N:P2O5: K2O]; iii) T3 = integrated nutrient management [INM- 50% RDF + compost 6 Mg ha−1 + biofertilizers (BF)]; iv) T4 = organic nutrient source [compost 6 Mg ha−1 + vermicompost (VC) 2 Mg ha−1 + castor neem cake (CNC) 250 kg ha−1 + BF + mulching]. Maximum mean groundnut pod yield (1.17 Mg ha−1) was recorded in T2 which was statistically similar to T4 (1.16 Mg ha−1). However, Mann-Kendall test for yield trend suggests the consistency in yield increase under T3 treatment during the last 16 years. The rate of pod yield enhancement was 27 kg ha−1 for every Mg increase in profile SOC stock. The mean SOC concentration (g kg−1) of 1-m soil depth increased from 4.0 to 5.6 (40%) in T4 over control and the mean SOC sequestration rate was 0.63 Mg C ha−1 yr−1. A minimum of 1.22 Mg C ha−1 yr−1 input was needed to maintain SOC stock at its antecedent level (zero change). We conclude that combined use of chemical fertilizers along with locally available organic resources is essential for enhancing SOC storage while achieving sustainable crop productivity in semi-arid agro-ecosystem