Precision Thermal Treatments, Atom Probe Characterization, and Modeling to Describe the Fe-Cr Metastable Miscibility Gap

The Fe-Cr metastable miscibility gap has been studied by high-precision thermal treatments, Vickers micro-hardness (HV) measurements, and atom probe tomography (APT). Thermodynamic modeling further supplements the experimental work. The results obtained show that recent thermodynamic descriptions of the metastable miscibility gap found in literature generally overestimates the consolute temperature. We can show that the source of ambiguity in previous studies is most likely a lack of clear distinction between Cr-Cr clustering and $$ \alpha^{\prime} $$ α ′ formation. This distinction is here made by APT results, and it leads to a determined consolute temperature of 580 ± 1 °C for Fe0.50Cr0.50. The revised thermodynamic modeling of the metastable miscibility gap captures the experimental results and is consistent with the overall picture from the Fe-Cr data in the literature. Graphic Abstract

EFFECT OF DEPOSITION PARAMETERS ON MICROSTRUCTURE AND TRIBOLOGICAL PROPERTIES OF HARD CA-PVD MULTICOMPONENT TiAlCrN AND TiAlCrCN COATINGS

Multicomponent TiAlCrN and TiAlCrCN coatings were deposited using vacuum arc evaporation technique on AISI 430 stainless steel. The influence of working gas pressure, C/N ratio, bias voltage on the structure and tribomechanical properties of the obtained coatings has been studied. The surface morphology, chemical compound of the coatings obtained under the various conditions has been analyzed by SEM with EDX, XRD, and XRF analysis. The dry wear pad-on-disc tests against 100Cr6 counterbody at 20 N load have been carried out. It was established that Vickers micro-hardness was varied from 26 to 41 GPa depending on deposition parameters.

Parametric Optimization of ZrB2–SiC Composites Sintered Through Microwave Sintering Using Grey Relational Taguchi

Zirconium Diboride (ZrB2) is known as an ultra-high temperature ceramic with applications in various industries like refractory and foundry industries. In conjunction with Silicon Carbide (SiC), ZrB2 ceramic finds extensive applications in the nose caps and leading edges of atmospheric re-entry vehicles and rocket propulsion. The primary objective is to optimize the output responses viz., Vickers micro hardness, relative density, compressive strength of ZrB2-30 vol.% SiC composites developed through microwave sintering. The three control factors viz., sintering temperature, heating rate and holding time are chosen as input process parameters for microwave sintering. Taguchi’s L9 orthogonal array is used to obtain experimental runs. The Grey Relational Taguchi provides the optimal process parameters by binding the multiple responses (relative density, vickers micro-hardness, and compressive strength) into single comprehensive response [i.e., Grey Relational Grade (GRG)]. The results confirm that the optimal parameters attained using Grey Relational Taguchi maximize the performance characteristics of the microwave sintering process.

Assessment of Sodium Thiosulfate Neutralizing Effect on Micro-hardness of Dentin Treated With Sodium Hypochlorite

Background The aim of this study is to evaluate the ability of sodium thiosulfate (STS) to reverse the adverse effect of sodium hypochlorite (NaOCl) on dentin microhardness. Methods Fifty single-rooted teeth were decoronated and longitudinally sectioned. The samples were divided into a control and four sample groups (n = 20): Normal saline for 15 min as the control group, G1: 2.5% NaOCl for 15 min without an incubation period, G2: 2.5% NaOCl for 15 min, G3: 2.5% NaOCl for 15 min irrigated with normal saline followed by 5% Na2S2O3 for 10 min, G4: Normal saline for 15 min followed by 5% Na2S2O3 for 10 min. All groups except G1 were incubated for 1 week. The microhardness measurements were determined using the Vickers micro-hardness test. Data were analyzed using the Kruskal-Wallis test for pairwise comparisons. A p-value < 0.05 was considered significant. Results All groups showed a significant decrease in the micro-hardness value compared with the control group. NaOCl for 1 week (G2) reduced the micro-hardness of dentine compared with samples, tested immediately after immersion in NaOCl (G1) (p < 0.05). NaOCl alone (G2) or treated with Na2S2O3 (G3) resulted in a significant decrease in microhardness compared with the Na2S2O3 group (G4) (p < 0.05). Conclusions Sodium thiosulfate as a neutralizing agent could not prevent the microhardness downturn caused by sodium hypochlorite

A Study of Composite Surface Hardness When Cured Using Special Accessories with a Curing Light

The study was carried out to compare the Vickers Micro-Hardness (VHN) of composite resin of different diameters (6 mm and 10 mm) prepared in a split mold. The 6 mm and 10 mm diameter composite resin samples were cured with the tip of a fiber optic light. Additional sample for same size were cured with the same tip after a mirror or a lens accessory was mounted to it. All the specimens were cured for 40 seconds. The hardness was calculated for both top and bottom at the center and the periphery. The results showed that the hardness of top surface was higher than that at the periphery. The mean hardness value for specimens cured with the light tip was higher than the hardness of specimens cured with their accessory. Conclusion mirror or lens didn’t potentiate light but distribute the energy to a larger area, resulting in less energy applied to the same small surface area, which reduced the hardness.

Mechanical Behavior and Microstructural Analysis of Molybdenum-TZM Alloy Subjected to Different Annealing Temperature

Mo-TZM alloy is one of the most famous economic molybdenum-based alloys. The percentage of chemical composition in mass of Mo-TZM alloy are Mo-0.5Ti-0.08Zr-0.03C. By adding some Titanium and Zirconium so that the mechanical properties and recrystallization temperature of molybdenum has been corresponding improvement. The purpose of this study is to determine the effect of different annealing temperature on mechanical properties of Mo-TZM alloy. The samples will be heated at two different temperature which are 1000 oC and 1300 oC in 1 hour and 40 minutes to change their microstructure behavior. The mechanical properties of the sample like hardness will be analyzed by using Vickers Micro hardness test. The force applied is 4.903 N and Vickers micro hardness number is 0.5 HVN for 10 second. Then to observe the microstructure changes, optical microscope and Scanning Electron Microscope (SEM) is be used. At annealing temperature 1000 oC, it show values of hardness is 249.54 VHN and the grain boundary size is 0.0898mm. While at annealing temperature 1300 oC, it show the lowest values of hardness which is 243.55 VHN and the highest grain boundary size which is 0.1068 mm. By doing annealing heat treatment it will decreases hardness values and increases the size of grain boundary

Spectroscopic and Mechanical Studies on the Fe-based Amorphous Alloy 2605SA1

The Vickers micro-hardness of this alloy was unusually dependent on the heat treatment from 300 to 634K, inferring important micro-structural changes and the presence of amorphous grains before its phase transition. Once the alloy is crystallized, the microhardness is characteristic of a brittle alloy, the main problem of these alloys. Within the amorphous state, other properties like free-volume, magnetic states and Fe-Fe distances were followed by PALS and MS, respectively, to analyze those micro-structural changes, thermally induced, which are of paramount interest to understand their brittleness problem.

Investigation of Mechanical Properties of Friction-welded AISI 304 with AISI 430 Dissimilar Steels

In this paper, standard SS304 austenitic stainless steel and SS430 ferritic steel cylindrical rods were fabricated by friction welding process by varying the frictional pressure and forge pressure in order to understand the effect of process parameter. The tensile strength and Vickers micro hardness tests were conducted for each fabricated joint to evaluate the mechanical properties of the welded specimen. It was found that sample S5 with friction pressure of 90 MPa and forging Pressure of 120 MPa has the high tensile strength value of 637 MPa and 372HV at the interface region. A detailed microstructural analysis was performed at the interface to reveal interconnecting of dissimilar metals.