Microstructural Analysis of TiC Reinforced Ferrous Surface Composites Processed by Accelerated Electron Beam Irradiation

The present study aims to analyze microstructures of TiC reinforced ferrous surface composites processed by accelerated electron beam irradiation. Two kinds of powder/flux mixtures, i.e., TiC and (Ti + C) powders with 40 wt% of CaF2 flux, were deposited evenly on an AISI 304 stainless steel substrate, which was then irradiated with electron beam. TiC agglomerates and pores were found in the surface composite specimen processed by irradiation of TiC powders because of insufficient melting of TiC powders. In the specimen processed by irradiation of Ti and C powders having lower melting points than TiC powders, a lot of large TiC carbides were precipitated in the melted region, together with a few TiC agglomerates or pores. This indicated the more effective TiC precipitation obtained from the melting of Ti and C powders, instead of TiC powders. The hardness of the surface composite layer was about two times higher than that of the AISI 304 substrate mainly due to the precipitation of TiC carbides. (C) 2001 Elsevier Science B.V. All rights reserved.11Nsciescopu

In-Situ Fracture Observation and Fracture Toughness Analysis of Ni-Mn-Ga-Fe Ferromagnetic Shape Memory Alloys

The fracture property improvement of Ni-Mn-Ga-Fe ferromagnetic shape memory alloys containing ductile gamma particles was explained by direct observation of microfracture processes using an in-situ loading stage installed inside a scanning electron microscope (SEM) chamber. The Ni-Mn-Ga-Fe alloys contained a considerable amount of gamma particles in beta grains after the homogenization treatment at 1073 K to 1373 K (800 A degrees C to 1100 A degrees C). With increasing homogenization temperature, gamma particles were coarsened and distributed homogeneously along beta grain boundaries as well as inside beta grains. According to the in-situ microfracture observation, gamma particles effectively acted as blocking sites of crack propagation and provided the stable crack growth, which could be confirmed by the R-curve analysis. The increase in fracture resistance with increasing crack length improved overall fracture properties of the Ni-Mn-Ga-Fe alloys. This improvement could be explained by mechanisms of blocking of crack propagation and crack blunting and bridging.open1123sciescopu

High strength aluminum alloys design via explainable artificial intelligence

Here, we have approached to discover new aluminum (Al) alloys with the assistance of artificial intelligence (A.I.) for the enhanced mechanical property. A high prediction rate of 7xxx series Al alloy was achieved via the Bayesian hyperparameter optimization algorithm. With the guide of A.I.-based recommendation algorithm, new Al alloys were designed that had an excellent combination of strength and ductility with a yield strength (YS) of 712 MPa and elongation (EL) of 19%, exhibiting a homogeneous distribution of nanoscale precipitates hindering dislocation movement during deformation. Adding Mg and Cu was found to be the critical factor that decides the relative ratio of strength and EL. We also demonstrate an explainable A.I. (XAI) system that reveals the relationship between input and output parameters. Our A.I. assistant system can accelerate the search for high-strength Al alloys for both experts and non-experts in the field of Al alloy design. (c) 2022 Published by Elsevier B.V

Effect of Interdendritic Precipitations on the Mechanical Properties of GBF or EMS Processed Al-Zn-Mg-Cu Alloys

The effects of nanoprecipitations on the mechanical properties of Al-Zn-Mg-Cu alloys after GBF (gas bubbling filtration) and EMS (electromagnetic stirring) casting were investigated. Dendritic cell structures were formed after GBF processing, while globular dendritic structures were nucleated after EMS processing. Equiaxed cell sizes were smaller in the EMS-processed specimens compared to the GBF-processed specimens, confirmed by EBSD (electron backscatter diffraction) analysis. Nanoprecipitations of eta & PRIME; phases inside of dendrites were observed by TEM (transmission electron microscope), and other Fe-bearing compounds were located in the dendritic boundaries. The yield strength of the T4 and T6 heat-treated specimens was close to 400 MPa and 500 MPa, respectively. Fractographic analysis was performed to investigate the effect of precipitations on tensile fracture.</p&gt

Pore formation mechanism and intermetallic phase transformation in Ti–Al alloy during reactive sintering

The mechanism of pore formation associated with intermetallic reaction is studied in sintered Ti50Al50 alloy with two different heating rates i.e. 1 °C/min and 10 °C/min. The heating rate significantly influences the pore parameters and the intermetallic reactions. The pore size and porosity increase with the extent of exothermic reactions during sintering. The intermetallic Ti2Al5 phase forms by a low-temperature solid-state diffusion of Al at the surface of Ti skeletons, while TiAl3 and TiAl2 intermetallic phases form at a high temperature owing to Ti2Al5 phase reaction with Al and Ti, respectively. A considerable change in thermal and volume expansion take place in the alloy heated with 10 °C/min compared to 1 °C/min. Therefore, it is found that the heating rate during sintering greatly influences the porous properties of Ti50Al50 by controlling the degree of exothermic reactions