Titanium Alloy Plates Research Articles

Macrostructures and mechanical properties in laser melting deposited titanium alloy plate at different thickness positions

Mechanical properties, including tensile properties and fatigue crack growth behaviors, and their relationships with macrostructures at different thickness positions in plates of laser melting deposited Ti–5Al–5Mo–5V–1Cr–1Fe, are experimentally investigated in this paper. It is observed that there display obvious differences in macrostructure features between overlap zones and non-overlap zones along thickness direction, which leads to anisotropies and heterogeneities of tensile properties including yield stress, tensile strength and total elongation. In fatigue crack growth tests with thin compact tension specimens at different thickness positions, crack paths are deviated from mode I with varying angles and fatigue crack growth rates display obvious fluctuations, which are mainly caused by the macrostructure features in overlap zone. In the end, evaluation methods are discussed for fatigue crack growth behaviors from the perspective of mechanics-materials interactive mechanisms, which helps strive for the future processing-material-structure-property-evaluation paradigm for additively manufactured metal structures.

Predicting metallic armour performance when impacted by fragment-simulating projectiles – Model adjustments and improvements

In a previous study, a set of nine existing penetration models for blunt projectiles were identified and reviewed for their ability to predict the plugging-mode ballistic limit velocity of monolithic titanium alloy, aluminium alloy, and steel plates. Assessed with a database of more than 650 experimental ballistic limit measurements, often at conditions beyond that for which they had been originally derived or validated, it was found that all nine models could predict the ballistic limit to within +/- 50% for more than 50% of the database entries. In this paper, simple modifications to these nine models are proposed that introduce empirical adjustments, reformulations of the target strength dependency, or a combination of both with the pragmatic goal of identifying a model suitable for application across the wide range of monolithic metallic targets impacted by different calibre fragment-simulating projectiles across a full range of ordnance and sub-ordnance velocities in our database. The modifications were able to improve the performance of all models across this range, with the best performing models able to predict the experimental ballistic limit to within +/- 10% for 50% of the database entries and to within +/- 20% for 76% of the database entries.

Mussel-Inspired Carboxymethyl Chitosan Hydrogel Coating of Titanium Alloy with Antibacterial and Bioactive Properties.

Infection-related titanium implant failure rates remain exceedingly high in the clinic. Functional surface coating represents a very promising strategy to improve the antibacterial and bioactive properties of titanium alloy implants. Here, we describe a novel bioactive surface coating that consists of a mussel-inspired carboxymethyl chitosan hydrogel loaded with silver nanoparticles (AgNPs) to enhance the bioactive properties of the titanium alloy. The preparation of hydrogel is based on gallic acid grafted carboxymethyl chitosan (CMCS-GA) catalyzed by DMTMM (4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride). To build a firm bonding between the hydrogel and titanium alloy plate, a polydopamine layer was introduced onto the surface of the titanium alloy. With HRP/H2O2 catalysis, CMCS-GA can simply form a firm gel layer on the titanium alloy plate through the catechol groups. The surface properties of titanium alloy were characterized by scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), and water contact angle. Silver nanoparticles were loaded into the gel layer by in situ reduction to enhance the antibacterial properties. In vitro antibacterial and cell viability experiments showed that the AgNPs-loaded Ti-gel possesses excellent antibacterial properties and did not affect the proliferation of rabbit mesenchymal stem cells (MSCs).

Impact and Ricochet of a High Speed Projectile from a Plate

A computational study of a projectile (either 2024 aluminum or TiAl6V4 titanium alloy) impacting a plate (either titanium alloy or aluminum) is presented in this paper. Projectile velocity (ranging from 250 m/s to 1500 m/s) with varying impact angles are considered. The presence of ricochet (if any) is identified over the ranges of the projectile velocity and impact angle considered. For the cases where ricochet is identified, the ricochet angle and velocity are predicted as functions of the incident angle and the incident velocity. The numerical results are compared with an analytical solution of the ricochet problem. The analytical solutions are from a model developed to predict the ballistic ricochet of a projectile (projectile) penetrator. The dynamics and the deformation of an aluminum (or a titanium alloy) projectile impacting on a finite thickness titanium alloy (or aluminum) plate are simulated. The current work is interesting in that it looks in the field of ballistics of different material combinations than are traditionally studied. The present simulations based on detailed material models for the aluminum and the titanium alloy and the impact physics modelling features in the LS-DYNA code provide interesting details regarding the projectile/plate deformations and post-impact projectile shape and geometry. The present results indicate that for no cases (for specified incoming velocities and impact angles considered) can an aluminum projectile penetrate a titanium alloy plate. The ricochet ‘mode predictions ‘obtained from the present simulations agree well with the ricochet ‘mode predictions’ given in an analytical model.

Forming mechanism and mechanical properties of dissimilar friction stir lap welds of 304 austenitic stainless steel to a Ti6Al4V alloy

Abstract A TC4 titanium alloy plate was lap joined to a 304 austenitic stainless steel plate via friction stir welding. The microstructures at the lap joint interface were intensively examined by means of energy dispersive X-ray spectroscopy and transmission electron microscopy analysis, and the mechanical properties of the lap joint were evaluated by a microhardness and shear tensile test. The results show swirling-like stir zones of TC4 and 304 SS are formed along the interface, where an aprox. 200 nm interface layer composed of TiFe and TiFe2 intermetallic compound is dispersed at the high rotating speed of the tool. In addition, the high hardness value is discontinuous distribution at the interface, and the shear strength of the commercially TC4 plate and 304 SS FSW lap joint can reach 7507 N at a rotational speed of 600 rpm, a welding speed of 30 mm/min, and a press amount of 0.4 mm.

Effect of deformation band on the strength of a rolled plate of intermetallic titanium alloy based on Ti–22Al–25Nb system

The influence of deformation band (DB) in a rolled plate of VTI-4 alloy of the Ti–22Al–25Nb system on the ultimate tensile strength (UTS) of this material in tensile tests has been studied. Samples subjected to heat treatment under the same conditions differ significantly in strength: 1075 MPa for the central part of the plate and 1150 MPa for the rest of the plate volume. It is shown that the spread in strength is determined by the presence of DB and the fraction of its area in the sample cross section. The presence of DB in a sample leads to reduction in its UTS by 3–6%, when the fraction of DB in a cross section of the test samples is 30–40% by area. It is found that the central part of the plate is a monograin, which has a thickness of ~1 mm and orientation 〈100〉β along the plate principal axes. The low strength of DB material is due both to the absence of grain-boundary hardening and unfavorable crystallographic orientation of monograin relative to the tensile load. The presence of the grain and texture inhomogeneity in a rolled plate leads to incorrect results of mechanical tests and could be a potential source of a fatigue failure.

Effects of rolling reduction on Burgers orientation relationship and slip behavior of a Ti–5.5Mo–7.2Al–4.5Zr–2.6Sn–2.1Cr alloy

The important but highly complex α/β Burgers orientation relationship and slip behavior of a Ti–5.5Mo–7.2Al–4.5Zr–2.6Sn–2.1Cr titanium alloy plate were obtained and elaborated, which was subjected to hot rolling with 20%, 40%, and 60% reductions in thickness. The electron backscatter diffraction statistical results showed that the Burgers orientation relationship was strictly maintained in the initial microstructure and exhibited a slight deviation of ∼10° at 20% reduction. With the thickness reduction increasing to 40% and 60%, this classical relation between α- and β-Ti will be gradually broken. Furthermore, the low-angle grain boundaries fractions of the β phase were 94.95% and 92.77% at 20% and 40% reductions, respectively, indicating that the β phase had a significant contribution to the overall plastic deformation. For the α phase, the relative frequencies of the <112¯0>{0001}α and <112¯0>{101¯0}α slip systems were 32.81% and 44.43% at 20% reduction, respectively. Noticeably, under the applied loading of normal direction, the <112¯0>{0001}α slip system became more pronounced at 60% reduction (i.e., 59.01%) and, hence promoted a considerable strain partitioning in the α phase. In terms of typical α grains, an obvious intragranular misorientation diversity at 60% reduction was further traced, thereby reasonably leading to the Schmid factor gradient within grain interior and the breakdown of Burgers orientation relationship.

Predicting metallic armour performance when impacted by fragment-simulating projectiles – model review and assessment

Metallic targets impacted by blunt-nosed, fragment-simulating projectiles typically fail via shear plugging. A number of models exist in open literature to predict the onset of this failure mode, which can be used to determine the ballistic limit velocity, VBL, for a particular combination of projectile and target plate. A set of nine existing penetration models for blunt projectiles were identified and reviewed for their ability to predict the plugging-mode ballistic limit velocity of monolithic titanium alloy, aluminium alloy, and steel alloy plates impacted by blunt-nosed, fragment simulating projectiles. A database of more than 650 experimental ballistic limit measurements was used to evaluate the performance of the predictive models, covering a wide range of ordnance and sub-ordnance velocities, normal and oblique impact angles, and target plate thicknesses. The range of experimental data typically exceeded that for which the applied models were derived or previously validated. Nonetheless, it was found that all nine models could predict the experimental ballistic limit to within +/- 50% of the experimental measurement for more than 50% of the ballistic tests considered.

Tensile properties analysis of CFRP-titanium plate multi-bolt hybrid joints

Hybrid joints have better tensile properties than pure bonded and bolted bolts, and are increasingly used in the aerospace field. Tensile tests are carried out for the Hybrid Bonded/Bolted (HBB) joints of Carbon Fiber Reinforced Polymer (CFRP) laminate and titanium alloy plate under different bolt numbers, and the corresponding load–displacement curves are obtained. At the same time, based on Continuum Damage Mechanics (CDM) theory, which is derived from 3D Hashin failure criteria, and a Cohesive Zone Model (CZM), the tensile strength prediction model of the composite laminate-titanium alloy plate multi-bolted HBB joint was established, and the numerical simulation results were in good agreement with the experimental height, which validate the feasibility of the model. The difference in the bearing capacity of HBB joints under different numbers of bolts is compared and analyzed. On this basis, the influence of inter-bolt distance on the tensile properties of the HBB joints is explored. The results show that the double-nail HBB joints can effectively improve the end warpage and low bearing capacity of the single-nail HBB joints. The tensile failure load of the double-nail HBB joints under the standard lap width (30 mm) is 82.6% higher than that of the single nail, the tensile failure load of the three-bolt HBB joints is 34.1% higher than that of the double nail. For the three-bolt HBB joint, the joint strength is controlled by the adhesive and the external bolt, while the internal bolt is redundant, the hybrid joint can be simplified by reducing the middle bolt. The inter-bolt distance has a great influence on the failure load of the hybrid joint. Increasing the inter-bolt distance can effectively improve the bearing capacity of the structure.

Melt flow and grain refining in laser oscillating welding of β-21S titanium alloy

Properties and serviceability of laser welded joints depend on the defect, weld geometry, and microstructures, which in turns are affected by molten pool behaviors. In this work, beam oscillation was used to improve microstructures and mechanical properties of welded joints by changing molten pool behaviors. The 2 mm-thick β-21S titanium alloy plates were welded using three beam oscillating modes (non-oscillation, transverse oscillation, and vertical oscillation). The molten pool behaviors for three oscillation modes were observed using high-speed cameras, and the weld morphology, microstructures and mechanical properties of the corresponding joints were examined. The results showed that defect-free joint with sound weld appearances could be achieved using beam oscillation that affected molten pool behaviors. The higher probability of equiaxed grain formation and significant grain refinement were found in the joints made using beam oscillation. The average grain sizes of welded joints for non-oscillating, transverse and vertical oscillating modes are 236, 184 and 168 μm, respectively. The welded joint made using beam oscillation also showed a higher tensile strength of 900 MPa at ambient temperature and 534 MPa at 450 °C. Furthermore, the Portevin-Le Chatelier (PLC) effect was observed in the stress-strain curves of welded joint at 450 °C, which was attributed to the precipitation of brittle ω phase.

Friction forge riveting: A new joining method for connecting 40Cr steel and TC4 titanium alloy

Bolted joints are usually used in connecting titanium alloy and steel structures in the shipbuilding industry, but bolted joints are easy to slip or loosen because of slamming and wave load. A new riveting process of friction forge riveting (FFR) was first proposed to connect 40Cr steel plate and TC4 titanium alloy plate through 40Cr rivets. Furthermore, joint formation, microstructures and mechanical performances of the FFR joints were studied. The results showed that the high loading speed led to the decrease of the fluidity of the rivet material and the increase of the root angle, which resulted in the rivet edge material thinning, stacking into a non-compact lamellar structure, accompanied by defects such as tunnels and flash. The heat generated by friction led to the re-austenitizing of the tempered sorbite. At different temperatures and cooling speeds, coarse and hard martensite structure was formed at the driven rivet head, and a pearlite band was generated in the riveting column. The hardness of the driven rivet head showed a regular circular distribution, and the hardness of riveting column center was obviously reduced. The best FFR joint was produced at the parameter of 2000 rpm rotating speed and 6 mm/min loading speed, of which the maximum cross-tension load and ultimate tensile-shear load were reaching 82% and 90% of the bolted joint respectively.

A Defect Detection Method for the Surface of Metal Materials Based on an Adaptive Ultrasound Pulse Excitation Device and Infrared Thermal Imaging Technology

Ultrasonic excitation has been widely used in the detection of microcracks on metal surfaces, but there are problems such as poor excitation effect of ultrasonic pulse, long time to reach the best excitation, and difficult to find microcracks. In this paper, an adaptive ultrasonic pulse excitation device and infrared thermal imaging technology have been combined, as well as their control method, to solve the problem. The adaptive ultrasonic pulse excitation device adds intelligent modules to realize automatic adjustment of detection parameters, which can quickly obtain reliable excitation; the multidegree-of-freedom base realizes the three-dimensional direction change of the ultrasonic gun to adapt to different excitation occasions. When the appropriate ultrasonic excitation makes microcracks in the resonance state, the microcracks can be frictionated, which produce heat rise with the temperature. Then, the microcrack defect can be detected by the infrared thermal instrument through the different surface temperatures with imaging recognition method. Our detection experiments of the titanium alloy plates and the aluminum alloy profiles of marine engineering show that the method can get reliable detection parameters in a short time and measure the crack length effectively. It can be used in many aspects such as crack detection in mechanical structures or complex equipment operating conditions and industrial production processes.

Inhomogeneity of microstructure in friction stir welded TC17 alloy joint and its effects on mechanical behavior

Friction stir butt welding was carried out to assemble 6 mm-thick TC17 titanium alloy plates with a W–Re weld tool. Inhomogeneous microstructures were obtained in stir zone (SZ) and heat affected zone (HAZ) of the weldment. A series of tests were conducted to reveal the influence of inhomogeneity of microstructure on mechanical behavior. Comparative refined β phase without precipitating secondary metastable microstructure generated a soft SZ and favored on the ductility of weldment. Strain localization during tension was promoted by the interface of HAZ and SZ that formed by thermal-mechanical coupling effects. Coincidentally, fatal fatigue cracks were verified to nucleate around the same region, and presented in a stress dependent mode.

Titanium alloy components fabrication by laser depositing TA15 powders on TC17 forged plate: Microstructure and mechanical properties

The manufacturing of titanium alloy components is of great significance for many industrial applications. High-performance titanium alloy parts are generally produced by a serial operation of hot forging process and extensive machining. Recently, additive manufacturing (AM) technologies such as direct laser deposition (DLD) has been developed to produce net-shape components. In this study, the parts were fabricated by depositing TA15 titanium alloy powders via DLD process on forged TC17 titanium alloy plates. Microstructure, microhardness and tensile properties of as-fabricated sample were examined. By using digital image correlation (DIC), the strain fields as well as the global strain behavior of the tensile specimen have been analyzed. The sample consists of three typical zones: the laser deposited zone (LDZ), the forged substrate zone (SZ), and the heat affected zone (HAZ) with good metallurgical bonding. Superfine basketweave microstructure forms within β grains in LDZ and HAZ because of fast cooling rate. The as-fabricated specimens have good tensile properties with an average ultimate tensile strength of 1027 MPa and average elongation of 4.57%. Non-uniform local strain concentration occurs in LDZ, while no strain concentration is found in HAZ and SZ. The remarkable non-uniformity of plastic strain is ascribed to different microstructures.

Investigation of Mechanical Properties of Polymer Coatings on Surfaces

In this work, the mechanical properties of organic coatings based on epoxy resin (DGEBA DER 332) and two diamines comonomers (IPD and 3DCM) on the surface of aluminum and titanium alloy plates were investigated. It has been proven that Young's modulus and internal residual stress of coatings depend on the thickness of the coating, the degree of reaction and the substrate material. During the thermal cure cycle, a loss of curing agent was observed and thus a change in the degree of reaction of the coating. The results showed that Young's modulus and stress of thin coatings are very different from volumetric values.

Microstructure and mechanical properties of TC4 titanium alloy K-TIG welded joints

The 12 mm-thick Ti–6Al–4V (TC4) titanium alloy plates were welded using keyhole tungsten inert gas (K-TIG) welding at various heat inputs. The microstructure, grain boundary (GB) characteristics and mechanical properties of the weld metal zone (WMZ) were analyzed. The test results show that the K-TIG welds are well formed, and no obvious defects are observed when the heat input is 2.30–2.62 kJ/mm. When the heat input gradually increases, α laths increase in length, and α′ phase and residual β phase are reduced. The electron backscatter diffraction (EBSD) test results indicate that the high-angle GB proportion in the WMZ increases with the increase of heat input. The tensile strength of the WMZ gradually decreases and the elongation of the WMZ increases when the heat input increases from 2.30 to 2.62 kJ/mm. The impact toughness of the WMZ increases as the heat input increases.

Clearance effect on the sheared edge characteristics of key chain cranioplasty plate in the punching process

Punching process is a process to cut sheet metal by pressing the workpiece until it exceeds the elastic limit of the material. In this study, the researcher used the finite element method as a solution to a problem during the manufacturing process. This research simulated the punching process, particularly hole-making, in keychain cranioplasty product to obtain smoothest sheared edge characteristics by optimising the clearance amount variations. The product had 1.53 mm diameter and 0.6 mm thickness of titanium alloy plate. The analysis was performed using the finite element method with the support of ANSYS Explicit Dynamic software. During the punching process, the punching speed was 2600 mm/min. The results showed that reductions in clearance, below 2.5% clearance, produced rougher sheared edge. The higher clearance produce rougher sheared edge. The 2.5% clearance was the standard for a right sheared edge to make a hole in the keychain cranioplasty plate with 0.6 mm thickness.

Osteogenesis and degradation behavior of magnesium alloy plate in vivo

Introduction: The magnesium alloy was fabricated into orthopedic plates, and used to repair tibial fractures of New Zealand white rabbits. The osteogenesis and degradation behavior of magnesium alloy plates were investigated in vivo. Methods: 38 rabbits were randomly divided into an experimental group using the magnesium alloy plate and control group using a titanium alloy plate. Tibial fractures in the experimental group and control group were fixed with magnesium alloy plates and titanium alloy plates, respectively. An X-ray of the fracture site was taken at 1, 2, 4, 8, and 16 weeks after surgery. The formation of callus and expression of bone morphogenetic protein (BMP-2) in each group were examined at 4, 8, and 16 weeks postoperatively. The degradation behavior of the magnesium alloy plate was observed using a scanning electron microscope with an energy dispersive spectroscopy system. Results: The results of X-ray showed that the fracture healed gradually and there was significant callus around the plate in the magnesium alloy plate group than that in the titanium alloy plate groups. The formation of callus and the expression of BMP-2 in the magnesium alloy plate group were more significant than that in the titanium plate group. The degradation behavior of the magnesium alloy plates deepened in vivo with the implantation time. Conclusion: The results demonstrated that the magnesium alloy plate implanted into the rabbit tibia could promote the formation of callus and result in osteogenesis in vivo. Meanwhile, the magnesium alloy plate was absorbed gradually in vivo.

Effect of Shielding Gas on Microstructures and Mechanical Properties of TC4 Titanium Alloy Ultranarrow Gap Welded Joint by Laser Welding with Filler Wire

A 20 mm thick TC4 titanium alloy plate was welded by ultranarrow gap laser welding with filler wire with Ar and He as shielding gas, respectively. A characterization analysis of the microstructures and mechanical properties of the welded joint was conducted with OM, SEM, XRD, and EBSD and through the microhardness test and tensile test. The results showed that HAZ of the welded joint formed with Ar as shielding gas was much wider than that with He, and weld microstructure composition with the two shielding gases was basically consistent; phase boundary of the weld metal obtained with Ar was clearer, with a larger misorientation between the laths; α′ martensite lath in weld metal prepared with He showed obvious preferred orientation distribution, and α′ martensite microstructure was much finer; the misorientation of α′ phase grain boundary of weld microstructure prepared with Ar was slightly less distributed in high angle grain boundary than that with He; tensile property of the welded joint prepared with He was better than that with Ar; the hardness of each zone of welded joint prepared with He was less fluctuated and the hardness value measured was slightly higher than that with Ar.

Deformation and Microstructural Analysis of Fiber Laser and TIG Welding of Thin Ti6Al4V Sheet by Coordinate Measurement Machine (CMM)

This paper reports on a study to compare the mechanical and deformation properties of Ti6Al4V titanium alloy joints between a pulsed fiber laser source and a tungsten inert gas (TIG) welding. Ti6Al4V alloy sheets - 0.8 mm thick-deformation modifications were investigated via a 3D laser scanner integrated to a portable-arm Coordinate Measurement Machine (CMM) and PC-DMIS software. Deformation pattern, residual distortions, weld geometry, microstructure and microhardnes properties of the joints produced with fiber laser source and tungsten inert gas welding were compared. Compared with the TIG, the welded by fiber laser has narrow heat affected zone (HAZ), small overall residual distortion, fine microstructure, high Vickers hardness. It can be concluded that fiber laser welding is more suitable for welding the thin Ti6Al4V titanium alloy plate than TIG welding; due to the small beam focus characteristics of fiber lasers enabiling deep penetration welding.