Effect of laser dwell time on pore elimination in powder bed fusion of metal matrix composites: experimentally validated modeling

Many studies have been conducted to better understand the relationship between additive manufacturing (AM) process parameters and the resulting structure and properties of manufactured parts. It is quite clear that defects associated with AM parts are detrimental to part performance and are thus a major concern for a broader application of AM processed parts. In this study, we aim to investigate the influence of process parameters such as laser dwell time in mitigating pore formation during powder bed fusion of AISI 316L austenitic stainless steel (SS316L)-WC composites. Single-track experiments are conducted with varying printing parameters, while discrete element modeling (DEM) is employed for simulating powder-bed packing for composite system. Results show that the filling of the pores between ceramic particles by the molten SS316L is dependent on the laser dwell time, which in turn, depends on the volume fraction of ceramic reinforcement and initial pore sizes between inclusions. Our experiments, in agreement with model analysis, show that with the information of the materials property of the metal phase in a composite system such as viscosity, surface energy and initial pore sizes between ceramic inclusions, the printing parameters can be chosen to yield the appropriate dwell time for pore free composites

Prediction of initial shape of functionally graded ceramic pre-forms for near-net-shape sintering

Sintering of macroscopically inhomogeneous ceramic components is always accompanied by shape distortions due to the difference in shrinkage rates of powder elements. The objective of the present investigation is the theoretical determination of initially distorted shapes of the green bodies needed to provide near-net-shape sintered components. Calculations are based on a finite element implementation of the continuum theory of sintering. In this theory, sintering is considered as a creep under the influence of the compressive “sintering stress”. To predict the initial shapes of the components the “inverse” numerical procedure is used when the component is assumed to swell from the final shape to the initial one under the influence of the pressure equal (with the exception of sign) to the sintering stress

Tolerability and Efficacy of Retard Form of Indapamide in the Treatment of Hypertension in Elderly Patients (Results of Multicenter Open Non-Comparative Trial in Russian Program ARGUS)

Open noncomparative multicenter study of tolerability and efficacy of a retard form of indapamide (1.5 mg o.d. for 3 months) in patients older then 55 years was conducted in 14 centers in Russia. Numbers of patients included into was analysis of safety and tolerability were 1277 and 1121, respectively. After 3 months systolic, diastolic and pulse blood pressure (BP) decreased by 20.2, 13.2, 27.5% (supine) and by 19.4, 11.8, 26.9% (standing), respectively. There were no significant changes of heart rate. Effect of treatment was considered positive in 92.4% of patients. Normalization of blood pressure occurred in 51.8% of patients (in 46.2% and 53.4% among men and women, respectively, p=0.0252; in 55.7% and 48% among patients aged 65 years, respectively). In patients with type II diabetes rates of positive effect and achievement of target BP <130/85 mm Hg were 60.8% and 31.4%, respectively. Hypokaliemia (3.0-3.5 mmol/l) was registered in 43 patients (3.4%), age of 27 of these patients was =65 years. There were no pronounced changes of blood serum levels of creatinine, glucose and uric acid. Significant lowering of atherogeneity cholesterol index occurred in the whole group while both this index and total cholesterol significantly decreased in patients with baseline hypercholesterolemia. Thus in patients older that 55 years monotherapy with retard form of indapamide was demonstrated to be safe and effective antihypertensive intervention

Tolerability and efficacy of retard form of Indapamide in the treatment of hypertension in elderly patients - (Results of multicenter open non-comparative trial in Russian program ARGUS)

Open noncomparative multicenter study of tolerability and efficacy of a retard form of indapamide 0.5 mg o.d. for 3 months) in patients older then 55 years was conducted in 14 centers in Russia. Numbers of patients included into was analysis of safety and tolerability were 1277 and 1121, respectively. After 3 months systolic, diastolic and pulse blood pressure (BP) decreased by 20.2, 13.2, 27.5% (supine) and by 19.4, 11.8, 26.9% (standing), respectively. There were no significant changes of heart rate. Effect of treatment was considered positive in 92.4% of patients. Normalization of blood pressure occurred in 51.8% of patients (in 46.2% and 53.4% among men and women, respectively, p=0.0252; in 55.7% and 48% among patients aged 65 years, respectively). In patients with type II diabetes rates of positive effect and achievement of target BP <130/85 mm Hg were 60.8% and 31.4%, respectively. Hypokaliemia (3.0-3.5 mmol/l) was registered in 43 patients (3.4%), age of 27 of these patients was =65 years. There were no pronounced changes of blood serum levels of creatinine, glucose and uric acid. Significant lowering of atherogeneity cholesterol index occurred in the whole group while both this index and total cholesterol significantly decreased in patients with baseline hypercholesterolemia. Thus in patients older that 55 years monotherapy with retard form of indapamide was demonstrated to be safe and effective antihypertensive intervention

Tolerability and efficacy of retard form of Indapamide in the treatment of hypertension in elderly patients - (Results of multicenter open non-comparative trial in Russian program ARGUS)

Open noncomparative multicenter study of tolerability and efficacy of a retard form of indapamide 0.5 mg o.d. for 3 months) in patients older then 55 years was conducted in 14 centers in Russia. Numbers of patients included into was analysis of safety and tolerability were 1277 and 1121, respectively. After 3 months systolic, diastolic and pulse blood pressure (BP) decreased by 20.2, 13.2, 27.5% (supine) and by 19.4, 11.8, 26.9% (standing), respectively. There were no significant changes of heart rate. Effect of treatment was considered positive in 92.4% of patients. Normalization of blood pressure occurred in 51.8% of patients (in 46.2% and 53.4% among men and women, respectively, p=0.0252; in 55.7% and 48% among patients aged 65 years, respectively). In patients with type II diabetes rates of positive effect and achievement of target BP <130/85 mm Hg were 60.8% and 31.4%, respectively. Hypokaliemia (3.0-3.5 mmol/l) was registered in 43 patients (3.4%), age of 27 of these patients was =65 years. There were no pronounced changes of blood serum levels of creatinine, glucose and uric acid. Significant lowering of atherogeneity cholesterol index occurred in the whole group while both this index and total cholesterol significantly decreased in patients with baseline hypercholesterolemia. Thus in patients older that 55 years monotherapy with retard form of indapamide was demonstrated to be safe and effective antihypertensive intervention

Tolerability and Efficacy of Retard Form of Indapamide in the Treatment of Hypertension in Elderly Patients (Results of Multicenter Open Non-Comparative Trial in Russian Program ARGUS)

Open noncomparative multicenter study of tolerability and efficacy of a retard form of indapamide (1.5 mg o.d. for 3 months) in patients older then 55 years was conducted in 14 centers in Russia. Numbers of patients included into was analysis of safety and tolerability were 1277 and 1121, respectively. After 3 months systolic, diastolic and pulse blood pressure (BP) decreased by 20.2, 13.2, 27.5% (supine) and by 19.4, 11.8, 26.9% (standing), respectively. There were no significant changes of heart rate. Effect of treatment was considered positive in 92.4% of patients. Normalization of blood pressure occurred in 51.8% of patients (in 46.2% and 53.4% among men and women, respectively, p=0.0252; in 55.7% and 48% among patients aged 65 years, respectively). In patients with type II diabetes rates of positive effect and achievement of target BP <130/85 mm Hg were 60.8% and 31.4%, respectively. Hypokaliemia (3.0-3.5 mmol/l) was registered in 43 patients (3.4%), age of 27 of these patients was =65 years. There were no pronounced changes of blood serum levels of creatinine, glucose and uric acid. Significant lowering of atherogeneity cholesterol index occurred in the whole group while both this index and total cholesterol significantly decreased in patients with baseline hypercholesterolemia. Thus in patients older that 55 years monotherapy with retard form of indapamide was demonstrated to be safe and effective antihypertensive intervention

Role of Cu During Sintering of Fe0.96Cu0.04 Nanoparticles

Nanoparticle agglomerates of passivated Fe (n-Fe) and Fe0.96Cu0.04 (n-Fe0.96Cu0.04), synthesized through the levitational gas condensation (LGC) process, were compacted and sintered using the conventional powder metallurgy method. The n-Fe0.96Cu0.04 agglomerates produced lower green density than n-Fe, and when compacted under pressure beyond 200 MPa, they underwent lateral cracking during ejection attributed to the presence of a passive oxide layer. Sintering under dynamic hydrogen atmosphere can produce a higher density of compact in n-Fe0.96Cu0.04 in comparison to n-Fe. Both the results of dilatometry and thermogravimetric (TG) measurements of the samples under flowing hydrogen revealed enhancement of the sintering process as soon as the reduction of oxide layers could be accomplished. The shrinkage rate of n-Fe0.96Cu0.04 reached a value three times higher than n-Fe at a low temperature of 723 K (450 A degrees C) during heating. This enhanced shrinkage rate was the manifestation of accumulation of Cu at the surface of the particles. The formation of a thin-surface melted layer enriched with copper during heating to isothermal holding facilitated as a medium of transport for diffusion of the elements. The compacts produced by sintering at 773 K (500 A degrees C), with relative density 82 pct, were found to be unstable and oxidized instantly when exposed to ambient atmosphere. The stable compacts of density more than 92 pct with 300- to 450-nm grain size could only be produced when sintering was carried out at 973 K (700 A degrees C) and beyond. The 0.22 wt pct residual oxygen obtained in the sintered compact is similar to what is used for conventional ferrous powder metallurgy products