Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userSimulation of the liquid pool for VT3-1 titanium alloy during vacuum arc remelting process
56
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
This article describes a simple heat model of the vacuum arc remelting (VAR) process that includes solution of the nonlinear heat conductivity equation with the nonlinear boundary conditions which are typical for VAR process. The finite-difference analogue of the model equations was obtained through the finite volume method. To check the efficiency of the simplified model that does not include magnetohydrodynamic phenomena in the liquid metal pool, the comparison has been made of the numerical calculation of the metal pool depth when melting the Russian titanium alloy VT3-1 with the results of radiographical tests. It was established that the model adequately describes the test data for various melting modes (ingot diameter and current strength).
rate research
Read More
Zr and Mo macrosegregations were investigated in Ti6246 titanium alloy industrial-scale ingotby vacuum arc remelting. The formation mechanism of Zr and Mo macrosegregations was studied during the solidification process. Zr macrosegregation was characterized by low content in the equiaxed grain zone and high content in the hot top zone. Mo exhibits an opposite trend with Zr. The macrosegregations of Zr and Mo were the most pronounced, with a statistic segregation degree higher than Al and Sn. It could be concluded that temperature gradient and solidification rate dominated the macrosegregation formations during the solidification process. The thermal buoyancy made the negative segregation Zr be continuously discharged to the front of the solid-liquid interface. Mo was enriched in the solid phase at the solid-liquid interface as the positive segregation.
The alpha/beta interface in Ti-6Al-2Sn-4Zr-6Mo (Ti-6246) is investigated via centre of symmetry analysis, both as-grown and after 10% cold work. Semi-coherent interface steps are observed at a spacing of 4.5 +/-1.13 atoms in the as-grown condition, in good agreement with theory prediction (4.37 atoms). Lattice accommodation is observed, with elongation along [-1 2 -1 0]alpha and contraction along [1 0 -1 0]alpha . Deformed alpha exhibited larger, less coherent steps with slip bands lying in {110}beta. This indicates dislocation pile-up at the grain boundary, a precursor to globularisation, offering insight into the effect of deformation processing on the interface, which is important for titanium alloy processing route design.
Machine learning (ML) is shown to predict new alloys and their performances in a high dimensional, multiple-target-property design space that considers chemistry, multi-step processing routes, and characterization methodology variations. A physics-informed featured engineering approach is shown to enable otherwise poorly performing ML models to perform well with the same data. Specifically, previously engineered elemental features based on alloy chemistries are combined with newly engineered heat treatment process features. The new features result from first transforming the heat treatment parameter data as it was previously recorded using nonlinear mathematical relationships known to describe the thermodynamics and kinetics of phase transformations in alloys. The ability of the ML model to be used for predictive design is validated using blind predictions. Composition - process - property relationships for thermal hysteresis of shape memory alloys (SMAs) with complex microstructures created via multiple melting-homogenization-solutionization-precipitation processing stage variations are captured, in addition to the mean transformation temperatures of the SMAs. The quantitative models of hysteresis exhibited by such highly processed alloys demonstrate the ability for ML models to design for physical complexities that have challenged physics-based modeling approaches for decades.
The mechanism of AgCl-induced stress corrosion cracking of Ti-6246 was examined at SI{500}{megapascal} and SI{380}{celsius} for SI{24}{hour} exposures. SEM and STEM-EDX examination of a FIB-sectioned blister and crack showed that metallic Ag was formed and migrated along the crack. TEM analysis also revealed the presence of ce{SnO2} and ce{Al2O3} corrosion products mixed into ce{TiO2}. The fracture surface has a transgranular nature with a brittle appearance in the primary $alpha$ phase. Long, straight and non-interacting dislocations were observed in a cleavage-fractured primary $alpha$ grain, with basal and pyramidal traces. This is consistent with a dislocation emission view of the the cracking mechanism.
We investigated the homogenous nucleation of the stoichiometric B2 and B33 phases in the Ni50Zr50 alloy using the persistent embryo method and the classical nucleation theory. The two phases become very close competitors at large supercoolings, which is consistent with the experimental observations. In the case of the B2 phase, the linear temperature dependence of the solid-liquid interface (SLI) free energy extrapolated to the melting temperature leads to the same value as the one obtained from the capillarity fluctuation method (CFM). In the case of the B33 phases, the SLI free energy is also a linear function of temperature at large supercoolings but the extrapolation to the melting temperature leads to a value which is considerably different from the CFM value. This is consistent with the large anisotropy of the SLI properties of the B33 phase nearby the melting temperature observed in the simulation of the nominally flat interface migration.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
