Titanium undergoes a phase transformation from hcp α to bcc β on heating and vice-versa on cooling through β transus temperature which provides a key in control of microstructure and texture while processing and during application of titanium alloys. Present study first makes a critical comparison between conventional experimental methods of β transus determination i.e., thermal scans and metallographic heat treatment, and CALPHAD predictions using TC-Python incorporating TCTI6 thermodynamic database. While experimental accuracy suffers from uncertainty in measurement systems and non-standardized measurement conditions, theoretical predictions perform below par for complex alloy systems with lower β transus. A data-driven statistical model using Ridge Regression Analysis (RRA) is shown to reduce the uncertainty in the CALPHAD predictions when employed over a web-based dataset consisting og sufficient number of alloys. [[EQUATION]] from RRA model are also found more accurate than other statistical models like Lasso and Random Forest Regressor irrespective of alloy composition input approaches (nominal composition vs. extrapolated [[EQUATION]] equivalent) and multi-elemental alloys. RRA modelling also outperforms CALPHAD predictions in the validation against experimental and reported [[EQUATION]] values for various titanium alloys, especially in nominal alloy composition inputs.

Present study reports site-specific microstructure development, porosity formation and micro-texture evolution in LMD processing of 17-4 PH SS and connects with localized mechanical response. A fully martensitic as-deposited microstructure with certain fraction of primary δ-ferrite from initial deposition at all locations along the build direction. Nearly constant melt pool size with similar geometry plus excellent adhesion between layers and absence of appreciable porosity with ~99.9% relative density for indicates suitability of optimized LMD parameters. Crystallographic texture and lattice strain exhibit distinct localized and site-specific characteristics depending on local thermal conditions in solidification and subsequent thermal cycling. Variations in micro-texture evolution is characterized byBD||<111> fiber texture at the bottom region that modifies to primary BD||⟨001⟩ plus secondary BD||⟨101⟩ fiber texture towards the middle region and finally culminating to weak BD||⟨101⟩ fiber texture at the top region. Micro-texture evolution along the build direction at these three locations (bottom, middle and top) altogether decided by a complex interplay between directional solidification through preferential epitaxial growth of favorably oriented primary δ-ferrite grains and subsequent orientation inheritance for transformed α' martensite variants. Retained lattice strain as a result of a balance between strain generation in rapid cooling and phase transformation and relaxation through recovery in subsequent thermal cycling subsequently attributes to a non-linear, near random hardness variation from bottom to the top region for the as-deposited block.

Laser hot wire direct energy deposited (LHW-DED) Ti-6Al-4V wall structures experience variable cooling rates along the build direction as heat accumulates with wall height. These variations in thermal history affect the microstructure, texture, and texture-mediated mechanical response within the walls. In the present work, site-specific texture in single-and multi-walled specimens and its concomitant effect on the localized mechanical properties are investigated via large-scale EBSD characterization and a polycrystal plasticity model based on the viscoplastic self-consistent (VPSC) framework. The effect of secondary process parameters, viz. interlayer delay and scan strategy, on the texture evolution was also examined. The results revealed that the transformed a and (prior) i texture intensities simultaneously increase with increasing wall height. The reconstructed parent i grain structure exhibits a strong cube texture with two a fibers, namely (0112)a and (1120)a aligned parallel to the build direction in both single-and multi-walled specimens. VPSC simulations revealed the role of site-specific texture in the tensile properties and anisotropic mechanical behavior of the walls.

The present study explores fine-scale microstructure, chemistry, and dislocation substructure formation, and their effect on phase decomposition and transformation during and after additive manufacturing (DED-LENSTM) of Ti-6Al-4V alloy. Optimized processing parameters were used to produce bulk alloy specimen. Electron microscopy was carried out to obtain details about microstructure and dislocation sub-structure formation as well as to analyze elemental distribution within the microstructural features. High temperature x-ray diffraction (XRD) and differential scanning calorimetry characterizations were conducted to study the phase transformation in as-deposited specimen. The prior β grain boundary regions either remain free from grain boundary (GB) α phase or contains smaller GB α variants. Lamellar α phase appears beside prior β grain boundaries while basket-weave structure with acicular α lamellae is present inside prior β grains. Larger primary and secondary acicular α lamellae evolve as part of basket-weave structure during deposition of a new layer, whereas refined tertiary and quaternary α lamellae form on reheating of previously deposited layers. Reheating also results in rearrangement of dislocations and α/α interface formation that assists β penetration and promotes spheroidization of α lamellae. β nucleation from retained dislocations inside α^' martensites further accelerates spheroidization. Morphology of different α/α′ phase along with substructure and nonequilibrium elemental distribution effects α → β phase transformation temperature post-deposition. The retained compressive residual stress also decreases with increase in temperature heat treatment and cause peak shifting and peak broadening in XRD pattern.

The present study explores microtexture development within the transformed microstructure of a DED LENS (TM) processed Ti-6Al-4V alloy. Lamellar alpha phase forms primarily beside beta grain boundary regions, whereas basket-weave structure having acicular alpha lamellae is noticed inside beta grains. Depending on the orientation of the adjacent beta grains, single or multiple grain boundary alpha variants occur at beta grain boundary regions. Single grain boundary alpha variant in turn leads to equally long lamellar alpha variants along the beta boundaries. Multiple grain boundary alpha variants on the other hand induce several lamellar alpha variants adjacent to them, frequently with differing orientations. The basket-weave structure inside a single beta grain contains all twelve possible alpha variants in beta ->alpha transformation. The transformed microstructure contains comparatively higher and lower frequency of 60 degrees/<112(sic)0>(alpha) and 10.53 degrees/<0001>(alpha) angle/axis misorientation combinations, respectively between adjacent alpha variants than that expected in ideal condition without variant selection. These aspects of micro-texture formation are ultimately shown to relate to the sequence of formation and orientation development for various microstructural features viz. beta grains in liquid ->beta transformation and grain boundary alpha, lamellar alpha, basket-weave alpha phases in beta -> alpha transformation during the course of DED LENS (TM) processing.

Present study reports the individual and synergistic effect of Mn and Zr solute addition to the stacking fault energy (SFE) of Al–Cu alloys through first principle-based density functional theory (DFT) calculations and experimental x-ray diffraction line profile analysis (XRDLPA). DFT calculations suggest that while Mn addition enhances SFE for Al–Cu–Mn alloys, Zr addition significantly lowers it for Al–Cu–Zr alloys with their co-addition in Al–Cu–Mn–Zr alloys producing an intermediate SFE. XRDLPA of these alloys in cold-rolled conditions validates the trend obtained from the theoretical calculations with consistency and absolute values to a satisfactory extent. Uniaxial tensile testing finally confirms SFE variation from the mechanical properties, especially the ductility of the cold-rolled alloys, which corroborates well with the variation in their strain hardening response as well.

The present study explores the micro-texture formation based on the morphology and orientation of the (3 grains, grain boundary (GB) alpha and lamellar or basketweave alpha phases and the subsequent effect on bulk texture evolution in Ti-6Al-4V alloy under (3 extrusion and (3 forging. The transformed microstructure of (3 extruded alloy is characterized by thick GB alpha plus lamellar alpha phases while (3 forged alloy contains thin GB alpha phase and acicular alpha lamellae forming basketweave structure plus lamellar alpha phase along the elongated prior (3 grain boundaries. The strength of the bulk alpha texture is comparatively higher for (3 forged alloy which is unusual. The reconstructed (3 microstructure contains elongated and equiaxed (3 grains for the two alloys, the former ones primarily contributing towards the (3 texture. Comparatively stronger transformation texture for (3 forged alloy comes from the long and continuous lamellar alpha phase beside adjacent elongated (3 grains as well as strong alpha variant selection within the basketweave structure. Multiple GB alpha variants at the (3 grain boundaries for (3 extruded alloy promotes an equally larger number of smaller lamellar alpha variants, thereby reducing the alpha variant selection and weaken the bulk texture. Formation of micro-textured regions within the transformed microstructure after (3 forging occur out of special (3 boundaries which strengthen the bulk alpha texture. Higher frequency of non-BOR related GB alpha phase on the other hand contributes to texture weakening through sympathetic nucleation of lamellar alpha phase in case of (3 extruded alloy.

Multidirectional fiber architecture for carbon fiber reinforced silicon carbide matrix (C f ‐SiC m ) composites considerably improves mechanical performance under complex loading conditions, thermal stability, and reliability when subjected to complex service conditions. A critical gap analysis however suggests the lack of any comprehensive study focusing on the microstructure evolution and small‐scale mechanical and tribological properties of these composites that encompasses all variants of fiber orientations. In the present study, noncrimped fabrics are employed for the fabrication of C f ‐SiC m composites by liquid silicon infiltration technique. Carbon fibers are stacked in unidirectional (1D) and multidirectional (2D, 3D, and 4D) configurations within the C f ‐C m preform. The composites are dense (density ranging from 2.20 g cm −3 for 3D to 2.23 g cm −3 for 2D) with relatively higher open (10.99% for 1D to 5.58% for 4D) and closed porosity (5.19% for 1D to 3.54% for 4D). The microstructure contains β‐SiC matrix, unreacted silicon and carbon fibers surrounded by secondary carbon matrix for all the composites. Multidirectional stacking offers an evenly distributed, more isotropic and densely packed fiber architecture with progressively larger gaps between similarly oriented fabric layers in 2D, 3D, and 4D composites. Hardness significantly increases for multidirectional fiber architecture compared to 1D composite (10.71 ± 4.48 GPa on longitudinal and 7.60 ± 2.21 on cross‐sectional surfaces) but differs between the longitudinal (ranging 14.40 ± 3.42 GPa for 2D to 18.51 ± 3.82 GPa for 4D) and cross‐sectional surfaces (ranging 8.43 ± 3.15 GPa for 2D to 10.22 ± 3.47 GPa for 4D). Iso‐strain hardness prediction in rule‐of‐mixture calculations closely matches the experimental hardness for all the composites, especially for the multidirectional ones, on the cross‐sectional surface, indicating similar straining for constituent phases when loaded parallel to the fiber direction. Marginal difference in coefficient of friction between longitudinal (ranging 0.40 ± 0.11 for 1D to 0.48 ± 0.12 for 3D) and cross‐sectional surfaces (tanging 0.63 ± 0.18 for 1D to 0.52 ± 0.14 for 4D in) on scratch testing plus minimal fluctuations of traction forces from longitudinal surface further proves the effectiveness of multidirectional 2D, 3D, and 4D composites.

The present study deals with the site-specific microstructure and porosity evolution, micro-texture and corresponding localized mechanical response of a Nickel-base superalloy (WSU 100) after laser metal deposition (LMD) processing. The as-deposited microstructure contains a sharp heterogeneity in size and geometry of the melt pools as well as development of heterogeneous melt pool microstructure due to the difference in thermal gradient and cooling rate in LMD processing. Identical gamma/gamma ' phase forms irrespective of the location within the specimen although a difference in the crystallite size and residual stresses occur at the bottom region. The as-deposited specimen contains various types of pores (both open and closed) having differences in size and sphericity and are heterogeneously distributed along the build direction. Micro-texture evolution is likewise location specific and varies from a weaker texture near the substrate due to a rapid, multidirectional and complex heating/cooling cycles to a stronger one at the middle region due to the long columnar grains out of the highest temperature gradient and again reverting to a relatively weaker texture near the top surfaces from rapid cooling with no further secondary heating. As a concomitant effect, significant hardness variation on the front surface is related to the local-scale heterogeneities and micro-texture evolution as well as the residual stresses from the LMD processing.

Auxetic lattices possess Negative Poisson's Ratio (NPR), which results in enhanced mechanical properties like indentation resistance, energy absorption etc. However, due to their lowered stiffness and low relative density, these lattices have limitations in structural applications. In this paper, a nesting strategy is proposed to enhance the stiffness of such materials. A thorough study, combining both numerical (finite element based) and experimental analyses, is presented to demonstrate the effectiveness of the proposed approach. It is shown that the proposed strategy can lead to high (similar to up to 17-fold) rise in stiffness whilst retaining significant auxeticity. The in-plane elastic properties have been experimentally determined by performing instrumented tensile tests involving Digital Image Correlation and correlation with the numerical data is established. Subsequently, the stress-strain behavior, specific energy absorption, strain to failure and the failure characteristics are presented confirming superior mechanical attributes of the Nested lattices. An important perspective is the effect of Fused Deposition Modelling process and its suitability for printing complex lattice structures.

The present study discuses microstructure evolution based on the morphology and orientation of prior β grains, grain boundary (GB) α and lamellar α phase and basket-weave structure for uniaxially β extruded and β forged Ti-6Al-4V alloys. Both the alloys contain elongated plus equiaxed β grains, although number of equiaxed β grains and their size is higher for β extruded alloy. Thick GB α and lamellar (α+β) colony structure is prevalent in β extruded alloy, whereas thin GB α and predominant basket-weave structure is observed in β forged alloy. Thin lamellar (α+β) colony is found only beside prior β grain boundaries of β forged alloy. The transformed microstructure contains large fraction of dislocations inside α & β phases and at the interfaces plus stacking faults inside α phase of β forged alloy. Lamellar α phase evolve following Burgers orientation relationship (BOR) with β grain, whereas GB α phase forms following BOR with one of the adjacent β grains. Non-BOR related GB α phase remains present in both the alloys following Potter or Pitsch-Schrader ORs. Non-BOR related lamellar α phase is also found in β extruded alloy. Orientation gradient inside β grains due to deformation and strong elemental partitioning for β extruded alloy cause higher fraction of non-BOR related α phase formation.

This research study explores the addition of chromium (Cr6+) ions as a nucleating agent in the alumino-silicate-glass (ASG) system (i.e., Al2O3-SiO2-MgO-B2O3-K2O-F). The important feature of this study is the induction of nucleation/crystallization in the base glass matrix on addition of Cr6+ content under annealing heat treatment (600 ± 10 °C) only. The melt-quenched glass is found to be amorphous, which in the presence of Cr6+ ions became crystalline with a predominant crystalline phase, Spinel (MgCr2O4). Microstructural experiment revealed the development of 200–500 nm crystallite particles in Cr6+-doped glass-ceramic matrix, and such type microstructure governed the mechanical properties. The machinability of the Cr-doped glass-ceramic was thereby higher compared to base alumino-silicate glass (ASG). From the nano-indentation experiment, the Young’s modulus was estimated 25(±10) GPa for base glass and increased to 894(±21) GPa for Cr-doped glass ceramics. Similarly, the microhardness for the base glass was 0.6(±0.5) GPa (nano-indentation measurements) and 3.63(±0.18) GPa (micro-indentation measurements). And that found increased to 8.4(±2.3) (nano-indentation measurements) and 3.94(±0.20) GPa (micro-indentation measurements) for Cr-containing glass ceramic.

Shear localization and shear band formation in metals, alloys and composites is an important deformation phenomenon most commonly associated with high strain rate deformation. It generally occurs as a thermomechanical instability where thermal softening due to adiabatic heating subdues strain hardening. The review presents different facets of strain localization and eventual shear band formation in various materials primarily including pure metals, alloys and composites. It starts with the dependence of shear band formation on materials parameters (e.g. crystal structure, stacking fault energy, c/a ratio, twining and TRIP effect etc.) and process variables (strain rate, stress states etc.) are presented. Effect of microstructural heterogeneities like twinning, grain boundary, phase boundary, particulates etc. are then discussed along with orientation variables (micro- and bulk texture etc.). Various aspects of microstructure and texture evolution due to strain localization in and around the shear bands are further demonstrated e.g. heat accumulation leading to dynamic recrystallization, phase transformation amorphization, evolution of Brass type texture due to shear banding etc. Theoretical simulations and modeling efforts pertaining to shear band formation, mostly crystal plasticity finite element based and resulting texture evolution is presented. Finally, an extensive review is carried out about the shear location and shear band formation for various metallic nanolayered composites. The present review therefore should be useful in understanding the root causes of shear localization and shear band formation e.g. during fabricating components for fracture-critical applications.

In the present study, 3D non-woven needle-punched preform (NPP) Cf–SiCm composite with 7.5 pct volume fraction of carbon fiber is prepared via liquid silicon infiltration technique and characterized for microstructure, phase formation and mechanical behaviors. Additionally, the composite is subjected to plasma arc jet tests for evaluation of ablation resistance under ultra-high temperature oxidation environment. The dense composite (density 2.5 to 2.6 g/cm3) contains β-SiC phase due to the reaction between infiltrated molten silicon and carbon matrix surrounding the carbon fibers. The resultant Cf–SiCm composite shows high hardness and high abrasion resistance due to a higher proportion of hard SiC matrix as well as exhibits various toughening mechanisms from the carbon fiber reinforcement causing a delay in fracture. It also contains excellent resistance to thermal shock and thermo-oxidative erosion resistance during plasma arc jet ablation test without any visible crack or damage on the exposed surface.

Welded structures are integral to complex bodies such as ships and offshore rigs. Welded joints are frequently used in connecting various plates and substructures, making their assessment pivotal. The numerical model used here consists of plates coupled using springs and dashpots. The coupling models the welded joint and exemplifies the uncertainties in the welding process. The joint identification algorithm systematically defines the coupling in two steps: first, by updating the model for spring stiffness and later, by identifying the dashpot coefficients. The dynamic characteristic is determined using a frequency response function (FRF). After model updating and damping identification, a comparison between the updated FRF and that obtained from the experimental modal test is carried out to ascertain the efficiency of the algorithm. Further, the test structure is subjected to experimental testing to correlate the results from the model updating with material properties. The experimental study includes tensile testing of the weld joints and microstructural analysis. The characterisation is carried out by partitioning the welded joint. The joint stiffness and damping are correlated to the stress-strain response and crystallographic texture of the welded plate.

The present study uses a diffusion-based approach to understand the effect of trace addition of a third solute atom (Mn and Zr as candidate element) in the coarsening kinetics of B' precipitates from a binary Al-Cu alloy system. Mn is more efficient in reducing the Cu interdiffusion flux and thereby restricting the precipitate coarsening compared to Zr. The theoretical outcome corroborates well with the experimental evidence from ternary Al-Cu-Mn and Al-Cu-Zr alloys.

In the present study, the objective is to examine the individual effect of varying the composition and SPS conditions on the final mechanical property (hardness) of alumina–zirconia (AZ) composites through their microstructural variations. To this end, AZ composites with varying zirconia (ZrO2) content are prepared vis-à-vis monolithic alumina (Al2O3) and zirconia (ZrO2) ceramics by spark plasma sintering (SPS). The microstructure evolution, phase formation, and hardness for the monolithic ceramics and AZ composites are systematically investigated and a correlation between them is established using various analytical modeling approaches. By altering the SPS temperature, significant variation in grain sizes were produced for the two monolithic ceramics and various AZ composites. In case of the latter, the size and volume fraction of secondary ZrO2 particles vary according to the composition, i.e., higher the ZrO2 content, coarser and numerous are the second phase particles. The monolithic ceramics exhibit comparatively lower hardness than the AZ composites at equivalent grain sizes. The hardness for the AZ composites and monolithic ceramics also vary marginally with the size of the matrix grains/crystallites. The variation in hardness is rather attributed to the volume fraction of the secondary ZrO2 phase in case of the AZ composites. Altogether, the AZ composite with a finer grain size and low volume fraction of secondary ZrO2 phase exhibits the highest hardness, while coarse-grained microstructure and high ZrO2 content contributes to significantly lower hardness. The present study thus emphasizes the synergistic roles of SPS temperature and composite compositions in dictating their microstructure and mechanical response.

Improving the productiveness of rock cutting bit is an essential requirement for sustain-able mining. Different heat treatment techniques are employed in the past to improve the proficiencies of cutting bits. Out of them, cryogenic treatment (CT) is accepted as a viable method for expanding the service life of a variety of cutting tool materials. The intention of the present study is to evaluate the effect of cryogenic treatment under varying soaking duration (12, 24 and 36 h) on hardness and wear resistance of WC-6%Co rock cutting bits. It also addresses the underlying mechanisms that CT carries in the modifications of micro-structure and phase transformation. The b-Co phase fraction has been significantly reduced due to cryogenic treatment. The wear resistance of both cryo-treated and un-treated bits was examined by scratch test and sliding wear test. From the results, an in-crease in hardness (CT 24-13.09 %) was observed as compared to UT, which is associated with a transformation from face-centered cubic a-cobalt (FCC a-Co) to hexagonal close -packed epsilon-cobalt (HCP epsilon-Co) phase due to cryogenic treatment. The coefficient of friction and wear resistance for the cryo-treated bits correspondingly increases in comparison to the untreated bit. CT 24 bit exhibits the maximum hardness of 2212 HV, an elevated COF (16.64 %) and the highest wear resistance (87.15 %) compared to UT and other CT bits. From the results, cryogenic treatment of cutting bits can be recommended for rock cutting application in mining industries. (c) 2023 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

This study aims to provide a comprehensive analysis on the effect of cryogenic treatment on two different grades of WC rock cutting bits (low cobalt grade: WC-9 wt% Co and high cobalt grade: WC-25 wt% Co). The cutting bits are exposed to cryogenic treatment at different holding time such as 12, 24 and 36 h. The treated and untreated bits are characterized for low temperature DSC, phase analysis, microstructural study, elemental composition, hardness, fracture toughness and scratch test. Phase shift was observed for both the cases due to the martensitic phase transformation from alpha-Co (fcc) to epsilon -Co (hcp) during cryogenic treatment. This transition was confirmed with low temperature DSC analysis between-90 degrees C and -60 degrees C. New eta carbide particles (Co6W6C) was formed for WC-25%Co and no such carbides was found for WC-9%Co. CT 36 of WC-25%Co exhibited a higher level of precipitation of eta carbides. The results show that CT has enhanced hardness for both low (14.08%) and high cobalt (23.34%) WC cutting bits compared to untreated bits whereas density is not altered evidently. CT 24 and CT 36 possessed higher hardness and lower fracture toughness for WC-9%Co and WC-25%Co respectively. Higher CoF and formation of tribo layer was observed for treated bits whereas untreated bit experiences surface fracture and cracks as a result of scratch test. As a finding, mining sectors can utilize cutting bits that have undergone sustainable cryogenic treatment for rock cutting applications.