xZr Alloys Research Articles

Effect of Zr content on the microstructure, mechanical properties, electrochemical behavior, and biocompatibility of Mg–3Zn–xZr alloy using powder metallurgy

Abstract In this study, Mg–3Zn–xZr (x = 0, 0.5, 1, 2 and 3) alloy were produced using powder metallurgy incorporating high-energy ball milling. Scanning electron microscope (SEM), energy dispersive X-ray (EDX) analyzer and X-ray diffraction (XRD) have been used to investigate the microstructure, chemical composition and phase distribution of the samples. XRD results show that the Mg solid solution wholly formed, and the milled powders were single phase, and no secondary phase was observed. While the secondary phases were formed after sintering. Hardness of Mg–Zn–xZr sample increased from 58.8 Hv (for Zr = 0) to 87.81 Hv with addition of 3 wt.% Zr. The result shows that the corrosion potential of Mg–Zn–Zr alloy was more positive than Mg–3Zn. However, the Mg–3Zn–Zr alloy exhibited higher corrosion current than Mg–3Zn due to galvanic effect of Zr rich area. All of Mg–3Zn–Zr alloys showed better antibacterial and biocompatibility properties than Mg–3Zn alloy due to the presence of Zr as additive. According to the mechanical, corrosion, and biological evaluations in this study, it can be concluded that the Mg–3Zn–1Zr alloy can be used as a suitable biomaterial for the use of orthopedic implants.

Dry Sliding Wear Behaviour of Al–7.6Si–xZr Alloys: Understanding the Impact of Zr on Wear Characteristics, Mechanics, and Transition

Dry Sliding Wear Behaviour of Al–7.6Si–xZr Alloys: Understanding the Impact of Zr on Wear Characteristics, Mechanics, and Transition

Cytocompatibility of Ti\u2013xZr alloys as dental implant materials

Ti–xZr (x = 5, 15, 25, 35, 45% wt%) alloys with low elastic modulus and high mechanical strength were fabricated as a novel implant material. The biocompatibility of the Ti–xZr alloys was evaluated by osteoblast-like cell line (MG63) in terms of cytotoxicity, proliferation, adhesion, and osteogenic induction using CCK-8 and live/dead cell assays, electron microscopy, and real-time PCR. The Ti–xZr alloys were non-toxic and showed superior biomechanics compared to commercially pure titanium (cpTi). Ti–45Zr had the optimum strength/elastic modulus ratio and osteogenic activity, thus is a promising to used as dental implants.

Effect of Hot Extrusion on Microstructure and Mechanical Properties of Mg–5Sn–xZr Alloys

The effects of Zr addition (0, 0.5 and 1 wt%) and extrusion ratio (6:1 and 12:1) on microstructure and mechanical properties of the Mg–5Sn alloy were studied. Results showed that the dendritic structure of the as-cast M–5Sn alloy gradually transformed into a nearly globular structure with Zr addition. The effect of Zr addition was evident through refining the microstructure, promoting the tendency to form partially divorced eutectic and increasing the Mg2Sn volume fraction, which improved the thermal stability of the alloy during homogenizing treatment at high temperatures. Hot extrusion was found to be very effective for enhancing both strength and ductility of the Mg–5Sn–xZr alloys. Grain refinement induced by twin dynamic recrystallization and dynamic precipitation of fine particles were realized as the main strengthening mechanisms of the extruded alloys. It was found that an increase of the extrusion ratio led to relatively coarser grains, lower yield strength, and higher hardening capacities. However, the Mg–5Sn–1Zr alloy extruded with the area-reduction ratio of 12 exhibited the best combination of tensile strength and elongation of 243 MPa and 10.6%, respectively. Moreover, tensile fracture studies revealed the intergranular cracking and quasi-cleavage fracture as the dominant fracture modes of the as-cast and extruded alloys, respectively.

Martensitic Transformation and Shape Memory Effect of Ti–16Nb–xZr (x = 0–8) Alloys

The influence of Zr content on the martensitic transformation behavior and shape memory effect (SME) was investigated to develop Ti–Nb–Zr high-temperature shape memory alloys. The addition of Zr decreases the peak temperature of the reverse martensitic transformation (Ap) by 19οC with 1 at % increase of Zr in the Ti–16Nb–xZr (x = 0–8) alloys, while it improves the stability of martensitic transformation by suppressing the formation of ω phase. At the same time, SME is enhanced greatly owing to the solution strengthening effect of Zr and the increase in the theoretical limit of transformation strain. The optimal Zr content for getting a high martensitic transformation temperature, an enhanced phase transformation stability and a good SME is determined to be 6 at %, where the martensitic transformation onset temperature (Ms) is 252οC and shape recovery ratio at the pre-strain of 8 is 90%.

Microstructure, mechanical properties, and preliminary biocompatibility evaluation of binary Ti-Zr alloys for dental application.

The microstructure, mechanical properties, and in vitro biocompatibility of vacuum-sintered Ti-xZr binary alloys (x = 5, 15, 25, 35, 45 wt%) were investigated. The results indicated that α and α' phase existed in Ti-xZr alloys. The hardness of the Ti-Zr alloys increased as the contents increased and ranged from 473 HV (Ti-5Zr) to 525 HV (Ti-45Zr). Increasing Zr content could lead to an increase in compressive and bending strength. Additionally, the Ti-45Zr alloy exhibited the maximum bending strength of 867.1 MPa and the maximum compressive strength of 1599.8 MPa which were much larger than that of CP-Ti. Moreover, all Ti-Zr alloys showed a lower elastic modulus (ranging from 53.5 to 59.3 GPa) compared with CP-Ti (103 GPa). The in vitro cytotoxicity tests were carried out for biocompatibility evaluation. The alloys presented no cytotoxic effects and the surface of the alloys exhibited great growth conditions for MG-63 cells. The Ti-45Zr alloy exhibited better mechanical properties and biocompatibility. In conclusion, Ti-45Zr alloy is of great potential for dental applications.

Assessment of Ti–16Nb–xZr alloys produced via PIM for implant applications

Titanium and its alloys are used in production of implants such as knee and hip prostheses due to their superior properties. Ti–Nb–Zr ternary alloys are preferred over other metallic implant materials due to the presence of non-toxic elements, high corrosion resistance, good biocompatibility, and proper mechanical properties. The aim of this work is to investigate the effect of zirconium addition on α → β phase transformation, microstructure, and mechanical behavior of Ti–16Nb alloy. In doing so, Ti–16Nb–xZr (x: 0, 5, 10, 15 mass%) alloys are produced by powder injection molding, which offers advantages such as low cost, net shape, and easy production of complicated parts for implant fabrication. X-ray diffraction analysis and scanning electron microscope images showed that zirconium behaves as a β stabilizer and according to differential thermal analysis, and it decreases α to β transition temperature approximately 30 °C. It is also revealed that increasing zirconium content caused finer microstructure and hardness of the alloy was raised from 336 HV0.5 to 412 HV0.5 while elastic modulus remains approximately steady between 103 and 110 GPa. It is concluded that Ti–Nb–Zr alloys have been found to be a good alternative to known metallic implant materials.

Effect of Zr on the microstructures and mechanical properties of as-extruded Mg–2.3Zn–0.18Y–xZr alloys

The microstructures and mechanical properties of as-extruded Mg–2.3Zn–0.18Y–[Formula: see text]Zr ([Formula: see text] = 0.03, 0.06 and 0.13 at.%) alloys and aged Mg–2.3Zn–0.18Y–0.13Zr alloy were studied. The results revealed that the microstructures of as-extruded Mg–2.3Zn–0.18Y–[Formula: see text]Zr alloys are typical bimodal structures. The coarse [Formula: see text]-Mg grains are surrounded by fine dynamically recrystallized [Formula: see text]-Mg grains. The average size of [Formula: see text]-Mg grains decreases with increasing Zr content. Moreover, the addition of Zr (at.%) can improve the mechanical properties of alloy. The as-extruded Mg–2.3Zn–0.18Y–0.13Zr alloy has the best mechanical properties with ultimate tensile strength (UTS) and yield strength (YS) of 346 MPa and 292 MPa, respectively, and an elongation of 26.7%, which can be attributed to the grain refining effect and precipitate strengthening. The UTS and elongation of Mg–2.3Zn–0.18Y–0.13Zr alloy changed slightly after aging treatment, but the YS increases remarkably, with the maximum increase of 30 MPa. The fracture surfaces of all alloys consist of many tearing ridges and dimples.

Surface Characteristics of Nanotube Formed Ti–25Nb–xZr Alloys.

The purpose of this study was to investigate surface characteristics of nanotube formed Ti–25Nb–xZr alloys. Ti–25Nb–xZr ternary alloys with 0–15 wt% Zr were manufactured in a vacuum arcmelting furnace. Ingots of the alloys were homogenized in an Ar atmosphere at 1000 °C for 12 h, followed by quenching in ice water. Nanotube layers were formed by an electrochemical method in 1 M H₃PO₄ and 0.8 wt% NaF at 30 V for 1 h. As the Zr content of the Ti–25Nb–xZr Alloys increased, the crystals transformed from a needle-like to equiaxed structure. Two nanotube sizes were obtained on the Ti–25Nb–xZr alloys. As the Zr content was increased, the diameters of the larger tubes decreased, whereas those of the smaller tubes increased. However, increased Zr content in the Ti–25Nb–xZr alloys had little effect on wettability.

Microstructure and High Temperature Impression Creep Properties of Mg–3Ca–xZr (x = 0.3, 0.6, 0.9 wt%) Alloys

The current study has investigated the influence of zirconium (Zr) addition to Mg–3Ca–xZr (x = 0.3, 0.6, 0.9 wt%) alloys prepared using argon arc melting on the microstructure and impression properties at 448–498 K under constant stress of 380 MPa. Microstructural analysis of as-cast Mg–3Ca–xZr alloys showed grain refinement with Zr addition. The observed grain refinement was attributed to the growth restriction effect of Zr in hypoperitectic Mg–3Ca–0.3 wt% Zr alloys. Heterogeneous nucleation of α-Mg in properitectic Zr during solidification resulted in grain refinement of hyperperitectic Mg–3Ca–0.6 wt% Zr and Mg–3Ca–0.9 wt% Zr alloys. The hardness of Mg–3Ca–xZr alloys increased as the amount of Zr increased due to grain refinement and solid solution strengthening of α-Mg by Zr. Creep resistance of Mg–3Ca–xZr alloys increased with the addition of Zr due to solid solution strengthening of α-Mg by Zr. The calculated activation energy (Qa) for Mg–3Ca samples (131.49 kJ/mol) was the highest among all alloy compositions. The Qa values for 0.3, 0.6 and 0.9 wt% Zr containing Mg–3Ca alloys were 107.22, 118.18 and 115.24 kJ/mol, respectively.

Microstructural evolution and thermal stability of Fe–Zr metastable alloys developed by mechanical alloying followed by annealing

The effect of Zr (up to 1 at.%) addition on the formation of Fe–Zr metastable alloys and their thermal stability were investigated for their possible nuclear applications. Fe–xZr (x = 0.25, 0.5, 1%) alloys were synthesised by mechanical alloying under a high-purity argon atmosphere using stainless steel grinding media in a SPEX 8000M high energy mill. The milling was conducted for 20 h with a ball-to-powder weight ratio of 10:1. The formation of metastable solid solutions after milling was confirmed from the change in the Gibbs free energy analysis as per Miedema’s model. The microstructural characterisation was carried out by analysis of X-ray diffraction, atomic force microscopy and transmission electron microscopy. The effect of Zr on the thermal stability of Fe–Zr alloys was investigated by extensive annealing experiments followed by microstructural analysis and microhardness measurements. The stabilisation was found to occur at 800 °C and thereafter, no significant change in the crystallite size was observed for the samples annealed between 800 and 1200 °C. The supersaturated solid solution, especially 1% Zr alloy, found to be highly stable up to 800 °C and the microhardness value of the same measured to be as high as 8.8 GPa corresponding to a crystallite size of 57 nm. The stabilisation effect has been discussed in the light of both the thermodynamic and kinetic mechanisms and the grain size stabilisation is attributed to the grain boundary segregation of Zr atoms and/or Zener pinning by nanoscale precipitation of the Fe2Zr phase.

Effects of Zr Content on the Microstructures and Tensile Properties of Ti–3Al–8V–6Cr–4Mo–xZr Alloys

The microstructural evolution and tensile properties of Ti–3Al–8V–6Cr–4Mo–xZr (x = 0, 2, 4 and 6) titanium alloys were investigated. The precipitated phases and tensile fracture morphologies were observed using scanning electron microscopy and transmission electron microscopy. Experimental results show that the presence of trace impurity Si and the addition of Zr induce the formation of (TiZr)6Si3 silicides. The quantity of silicides increases with Zr content increasing. The dispersed silicides refined the grain size of β Zr-containing alloys, and the grain size decreases significantly with Zr content increasing. Accompanying these microstructural changes, the strength of the alloys is enhanced gradually with the increase of Zr content, which is attributed to the combination of precipitation strengthening and grain refinement.

Mechanical and electrochemical characterisation of new Ti–Mo–Nb–Zr alloys for biomedical applications

The development and characterisation of new metallic biomaterials that contain non-toxic and non-allergic elements but possess low elastic modulus and low biodegradation rates, has become a topic of serious investigation in orthopaedic implant application. The lowering of elastic modulus and improving of corrosion resistance can be achieved by specific chemical alloying and super-elasticity effects, associated with a stress-induced phase transformation from the BCC metastable beta phase to the orthorhombic α″ martensite. Using this framework, this paper focuses on the effect of Nb and/or Zr micro-additions on the elastic modulus/yield strength balance and discusses microstructure, and the mechanical and electrochemical behaviour of four new β-Ti–8Mo–xNb–xZr (x=2–5) alloys, using tensile tests, X-ray diffraction, SEM characterisation, ultrasound technique and potentiodynamic polarisation methods. The results reveal that the alloys exhibit a pronounced microstructural sensitivity response, with alloying elements and excellent agreement between β-stability and high mechanical strength, with increasing Nb additions. Although all the alloys possess excellent corrosion resistance and low Young׳s modulus, Ti–8Mo–4Nb–2Zr alloy, which consists of β+α′′ phases, exhibits a low Young modulus of 35GPa, which is lower than those of the commercial alloys already used in biomedical implantation. The significant corrosion resistance, nontoxicity and better mechanical compatibility are properties pertinent to preventing stress shielding and bone resorption in orthopaedic implant applications.

Development of Zn–15Al–xZr filler metals for Brazing 6061 aluminum alloy to stainless steel

Brazing of a 6061 aluminum alloy to 304 stainless steel has been conducted using a Zn–15Al–xZr filler metal and the effects of Zirconium (Zr) addition on the properties and microstructures of Zn–15Al filler metals were investigated. The experimental results indicated that the liquidus temperature of Zn–15Al–xZr was approximately 445°C and Zr addition had little influence on the melting point of the Zn–15Al–xZr filler metal. Moreover, adding an appropriate amount of Zr appeared to refine the η-Zn dendrites and improve the microstructure of the filler metal. However, an excessive amount of Zr led to the formation of Zr-bearing compounds in the Zn–15Al–xZr alloy. The results also indicated that the thickness of the intermetallic compound layer of Fe4Al13 along the brazed seam/stainless steel interface was significantly reduced and a layer as thin as 0.93μm was observed at the interface of Zn–15Al–0.2Zr brazed joint. This imparted a 10% increase to the average shear strength of the joints brazed with Zn–15Al–0.2Zr in comparison to the Zn–15Al filler metal.

Highly ordered nanotubular film formation on Ti–25Nb–xZr and Ti–25Ta–xHf

The purpose of this study was to investigate the highly ordered nanotubular film formation on Ti–25Nb–xZr and Ti–25Ta–xHf, examining the roles of niobium, zirconium, tantalum and hafnium alloying elements. The Ti–25Nb–xZr and Ti–25Ta–xHf ternary alloys contained 0, 7 and 15wt.% of these alloying elements and were manufactured using a vacuum arc-melting furnace. Cast ingots of the alloys were homogenized in Ar atmosphere at 1050°C for 2h, followed by quenching into ice water. Formation of nanotubular films was achieved by an electrochemical method in 1M H3PO4+0.8wt.% NaF at 30V and 1h for the Ti–25Nb–xZr alloys and 2h for the Ti–25Ta–xHf alloys. Microstructures of the Ti–25Ta–xHf alloys transformed from α″ phase to β phase, changing from a needle-like structure to an equiaxed structure as the Hf content increased. In a similar manner, the needle-like structure of the Ti–25Nb–xZr alloys transformed to an equiaxed structure as the Zr content increased. Highly ordered nanotubes formed on the Ti–25Ta–15Hf and Ti–25Nb–15Zr alloys compared to the other alloys, and the nanotube layer thickness on Ti–25Ta–15Hf and Ti–25Nb–15Zr was greater than for the other alloys. Nanotubes formed on Ti–25Ta–15Hf and Ti–25Nb–15Zr showed two sizes of highly ordered structures. The diameters of the large nanotubes decreased and the diameters of the small nanotubes increased as Zr and Hf contents increased. It was found that the layer thickness, diameter, surface density and growth rate of nanotubes on the Ti–25Ta–xHf and Ti–25Nb–xZr alloys can be controlled by varying the Hf and Zr contents. X-ray diffraction analyses revealed only weak peaks for crystalline anatase or rutile TiO2 phases from the nanotubes on the Ti–25Nb–xZr and Ti–25Ta–xHf alloys, indicating a largely amorphous condition.

Oxidation behavior of Zr-containing Ti2AlNb-based alloy at 800 °C

The oxidation behavior of Ti–22Al–(27–x)Nb–xZr (x=0, 1, 6) alloys at 800 °C for exposure time up to 100 h was examined. It is shown that oxidation rate of experimental alloys obeys the parabolic kinetics. Ti–22Al–26Nb–1Zr alloy demonstrates more excellent oxidation resistance than the other two alloys. The main oxidation products are TiO2, Al2O3 and AlNbO4 phases for all these alloys. For the Ti–22Al–26Nb–1Zr alloy, Zr addition can modify the growth mechanism of oxide scale, which can effectively hinder the diffusion of oxygen. Whereas, reaction of Zr with oxygen leads to the formation of ZrO2 precipitates for the Ti–22Al–21Nb–6Zr alloy, which promotes the oxygen ingress into the substrate. Meanwhile, oxidation affected zones, including internal-oxidation layer and oxygen-enriched zone, are present beneath the outmost oxide scale. The difference in these zones is derived from the phase constitution in the starting Ti–22Al–(27–x)Nb–xZr (x=0, 1, 6) alloys.

Control of nanotube shape and morphology on Ti–Nb(Ta)–Zr alloys by varying anodizing potential

Different applied potentials have been employed in a two-step anodization process, utilizing a 1M H3PO4 electrolyte and a solution containing this electrolyte and 0.8wt.% NaF, to control the shape and morphology of oxide nanotubes on coatings for ternary Ti–30Ta–xZr alloys. The ternary alloys were manufactured using an arc furnace, and corrosion testing was carried out using a potentiostat. The microstructures of the Ti–30Ta–xZr alloys had a needle-like structure, and the lath thickness of the α′ phase increased as the Zr content increased. The microstructures of Ti–30Nb–xZr alloys had equiaxed grains. The Ti–30Nb–xZr alloys showed smaller micropores and nanotubes compared to the Ti–30Ta–xZr alloys. The Ti–Nb(Ta)–Zr alloys tended to have improved corrosion resistance with increasing Zr content.

Effect of zirconium content on the microstructure, physical properties and corrosion behavior of Ti alloys

A series of Ti–xZr alloys with Zr contents ranging from 5 to 20wt% was prepared and the effects of Zr addition on the microstructure, physical properties, and corrosion behavior of Ti alloys were investigated. The phase and microstructures were characterized using X-ray diffractometry (XRD), optical microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The Ti–xZr alloys exhibited α-Ti structure at Zr content of 20wt% or below. Commercially pure titanium (cp-Ti) was used as a control. We also investigated the effects of alloying element Zr on the mechanical property, oxidation protection ability, and corrosion behavior of Ti–xZr binary alloys. The physical properties and corrosion behavior of Ti–xZr alloys were sensitive to the Zr content. The addition of Zr did contribute to the hardening of cp-Ti due to solid-solution strengthening of α-Ti. Ti–xZr alloys containing up to 10wt% Zr resulted in good oxidation resistance, while Ti–xZr alloys with above 10wt% Zr demonstrated higher oxidation weight gain than cp-Ti. Electrochemical experiments showed that the Ti–xZr alloys exhibited better corrosion resistance compared to that of cp-Ti.

Surface characteristics of hydroxyapatite coatings on nanotubular Ti–25Ta–xZr alloys prepared by electrochemical deposition

The surface characteristics of hydroxyapatite coatings on nanotubular Ti–25Ta–xZr alloys prepared by electrochemical deposition for dental implants have been investigated using various methods. The Ti–25Ta–xZr alloys were prepared by an arc melting furnace, homogenized for 12h at 1000°C in an argon atmosphere, and then water-quenched. Nanotubular structures were formed by an electrochemical method in 1M H3PO4 electrolytes containing 0.8wt.% NaF. Electrochemical deposition was carried out using a cyclic voltammetry method over a potential range of −1.5V to 0V at 80°C in a 5mM Ca(NO3)2+3mM NH4H2PO4 solution. Surface characteristics were observed by optical microscopy, X-ray diffraction, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, contact angle goniometer, and image analyzer software. Microstructures of the Ti–25Ta–xZr alloys changed from α″ phase to β phase, and the phases changed in morphology from a needle-like to an equiaxed structure with increasing Zr content. The arrangement of nanotubes changed from an irregular distribution to a high level of ordering surrounded by smaller tubes, and the occupied percentage of pore wall surface decreased from 28% to 23%, as the Zr content increased. HA precipitates also changed in morphology from a plate or leaf-like shape to a needle or flower-like shape as the Zr content increased.

Surface morphology of TiN-coated nanotubular Ti–25Ta–xZr alloys for dental implants prepared by RF sputtering

The surface morphology of TiN-coated nanotubular Ti–25Ta–xZr alloys prepared by radio-frequency sputtering for dental implants was investigated. Ti–25Ta–(0–15wt.%) Zr alloys were initially formed in an arc-melting vacuum furnace, homogenized for 12h at 1000°C, and water-quenched. Formation of a nanotubular structure was achieved on the alloys by anodization at room temperature in 1M H3PO4 electrolytes containing 0.8wt.% NaF. A TiN coating was then placed on the alloys using a radio-frequency magnetron sputtering technique. These depositions were performed on the alloy substrates using pure Ti targets. Surface morphologies of the nanotubular alloys were examined by a variety of instruments. The nanotube diameters on Ti–25Ta, Ti–25Ta–3Zr and Ti–25Ta–7Zr had irregular distribution, while the nanotubes on Ti–25Ta–15Zr had a more regular pattern of large tubes surrounded by several smaller tubes. As the Zr content in these alloys increased, the average thickness of the TiO2 nanotubes increased. At high Zr content, the surface of the nanotubes was covered with the TiN film. The Zr content affects the Ra and wettability, providing a hydrophilic property.