Al3Zr Phase Research Articles

Relationship Between the Thermodynamic Parameters, Structure, and Anticorrosion Properties of Al-Zr-Ni-Fe-Y Alloys

The influence of the chemical composition on the crystallization process, amorphous phase formation, and the anticorrosion properties of Al-Zr-Ni-Fe-Y alloys are presented. To reduce the number of experiments, a thermodynamic approach was applied in which the entropy and Gibbs free energy of representative alloys were optimized. The low glass-forming ability of Al-Zr-Ni-Fe-Y alloy systems was related to the crystallization of the Al3Zr phase from the melt. The structural analysis showed that phases containing Ni and Fe, such as Al19Ni5Y3, Al10Fe2Y, and Al23Ni6Y4, played a key role in the formation of amorphous alloys. According to this, the simultaneous addition of Ni/Fe and Y is important to prevent the crystallization of Al-based alloys in the melt. The formation of an amorphous phase in Al80Zr5Ni5Fe5Y5 alloys and the complete amorphization of Al85Ni5Fe5Y5 alloys were responsible for the high corrosion resistance compared with fully crystalline alloys. Moreover, the addition of Y had a significant impact on the anticorrosion properties. The XPS results showed that the alloys tended to form a passive Al2O3 and Y2O3 layer on the surface.

Effects of Ti–B and Si additions on microstructure and mechanical properties of Al–Cu–Mg based aluminum matrix composites

Ti–B and Si were added to an Al–Cu–Mg alloy to form various reinforcement phases. Various methods for characterizing reinforcement and bulk materials of the aluminum matrix composite (AMC) were investigated. A primary α-Al lamellar structure composed of α-Al and Al2CuMg (S) and Al3Zr phases was formed in Base alloy. The formation of the Al3Zr phase was suppressed and the Al3(Zr,Ti) phase and TiB2 particles were additionally observed in the Ti–B added alloy. Meanwhile, Mg2Si (β), Al2Cu (θ) and Al5Cu2Mg8Si6 (Q) phases were formed, and the Al2CuMg (S) phase disappeared in the Si added alloy. We deduced that Mg2Si (β) and Al5Cu2Mg8Si6 (Q) phases are preferentially formed over the Al2CuMg (S) phase, with the result that the total fraction of Mg in the matrix is decreased in Si added alloy. Several methods for measurement of mechanical properties in AMCs were attempted. Strength was evaluated by compression tests and tensile tests, in which was difficult because of the formation of a brittle Al3(Zr,Ti) phase in the AMCs. Micro Vickers and Brinell hardness tests were conducted to evaluate the hardness of the reinforcement and bulk material, respectively. Nanoindentation has advantages in evaluating the properties of each reinforcement phase, and RUSPec is suitable for evaluation of the bulk unit characteristics of AMCs.

The Effects of Zr Addition on the Microstructure and Mechanical Properties of A356–SiC Composites

The influences of Zr on the microstructure of A356–15 vol% SiC composites, such as the distribution of SiC particles in the matrix, the grain size and the hardness and impression creep between 225 and 275 °C, were examined. These composites were prepared using the stir casting technique. The addition of Zr forms Al3Zr phases, which can act as heterogeneous nucleation sites, thus resulting in grain refinement. Furthermore, Zr leads to a more uniform distribution and an increased area fraction of SiC particles. Moreover, the addition of only 0.1 wt% Zr significantly increased the Brinell hardness by approximately 18% when compared to the composite without added Zr. The addition of a small amount of Zr (0.1 wt%) is sufficient to increase the Vickers microhardness by approximately 34% when compared to the composite without added Zr, indicating the effect of solid solution strengthening on the composite matrix. The high-temperature stability test using the impression creep technique demonstrated that the A356–15 vol% SiC composite with 0.1 wt% added Zr shows improved creep resistance. However, the creep resistance of composite samples with higher than 0.1 wt% added Zr decreases due to grain boundary sliding occurring in the A356–15vol% SiC composites with too much added Zr.

Individual/synergistic effects of Al and AlN on the microstructural evolution and creep resistance of Elektron21 alloy

The creep properties of Mg-2.85Nd-0.92Gd-0.41Zr-0.29Zn (El21) alloys with additions of 0.25 wt% Al, 0.75 wt% AlN and 1 wt% AlN/Al nanoparticles (NPs) were studied over a stress range from 80 to 140 MPa at 240 °C, respectively. The individual/synergistic roles of Al and AlN in the El21 alloy were investigated systematically to reveal their creep strengthening mechanisms. Creep results show that individually all three additions of 0.25 wt% Al, 0.75 wt% AlN and 1 wt% AlN/Al could increase the creep resistance of El21 alloy apparently. However, the addition of mixed 1 wt% AlN/Al NPs shows the best strengthening effect on creep properties in El21 alloy. Microstructural characterizations reveal that the additions of Al and AlN increased the area fraction of intermetallic particles obviously. Blocky Al2Zr, Al2Zr3 particles and Al2(Nd, Gd) (Al2RE) particulates were observed in both El21 + 0.25% Al and El21 + 0.75%AlN. Nevertheless, when Al and AlN were simultaneously added into El21 alloy the formation of these blocky phases Al2Zr/Al2Zr3 was suppressed, and a larger amount of Al2RE phase was observed. This is attributed to the preferential reaction between AlN and Zr, which restricted the formation of Al–Zr phase and subsequently promoted the reaction of Al-RE phase. The dominant mechanism during creep at 240 °C was calculated to be viscous glide of dislocation. The simultaneous additions of Al and AlN NPs could lead to a more homogeneous distribution of intermetallic particles and increase the amount of Al2RE phase. Such kind of microstructures is beneficial for hindering the dislocation movement, transfer the load from matrix and alleviate the local stress concentration. Consequently, El21 + 1% AlN/Al exhibits the best creep properties among four alloys.

Ultrasound induced fragmentation of primary Al3Zr crystals

Ultrasonic cavitation melt treatment (UST) of aluminium alloys has received considerable attention in the metal industry due to its simple and effective processing response. The refined primary intermetallic phases formed in the treated alloys during controlled solidification, govern alloy structural and mechanical properties for applications in the automotive and aerospace industries. Since the UST is performed close to the liquidus temperatures of the alloys, understanding the refinement mechanism of the primary intermetallic phases has been beset by difficulties in imaging and handling of liquid metals. In this paper, the sonofragmentation behaviour of primary intermetallic Al3Zr crystals extracted from the matrix of an Al-3 wt% Zr alloy and fixed on a solid substrate was investigated. The intermetallics were exposed to cavitation action in deionized water at 24 kHz of ultrasound frequency. The fragmentation mechanism from the nearby collapsing cavitation bubbles was studied with in-situ high speed imaging. Results revealed that the main fragmentation mechanism is associated with the propagation of shock wave emissions from the collapsing bubble clouds in the vicinity of the crystal. The mechanical properties of the Al3Zr phase determined previously were used for the fracture analysis. It was found that an Al3Zr intermetallic undergoes low cycle fatigue fracture due to the continuous interaction with the shock wave pressure. The magnitude of the resulting shear stress that leads to intermetallic fragmentation was found to be in the range of 0.6 – 1 MPa.

Ultrasonic processing of aluminium alloys above the liquidus: the role of Zr

Ultrasonic melt processing (USP) is gaining quite an interest in recent years due to the benefits of this technology to the melt quality and structure refinement. A number of mechanisms have been identified that govern the effects of USP at different stages of melt processing. Technologically it is advantageous to apply USP to the fluid melt rather than to a mushy solidifying alloy. In this case heterogeneous nucleation on available or activated/multiplied substrates is the main mechanism. Among these substrates, primary crystals of Al3Zr phase were shown to be potent and effective. This paper gives a review of the own research into the role of Al3Zr in structure refinement in various groups of Al alloys, from solid-solution type to hypereutectic. This overview includes the evidence of a possible eutectic reaction between Al and Al3Zr in Al-rich alloys, mechanisms of Al3Zr formation and refinement under USP (that enables these primary crystals to be active substrates for Al and some other primary phases), the role of USP in facilitating primary solidification of Al3Zr in the Al-Zr system, and the additional benefits of solute Ti presence. The paper is illustrated with the data obtained over the last 15 years of research led by the author.

Simultaneous Increase of Electrical Conductivity and Hardness of Al–1.5 wt.% Mn Alloy by Addition of 1.5 wt.% Cu and 0.5 wt.% Zr

The effect of Cu and Zr additions and annealing temperature on electrical conductivity and hardness of the Al–1.5 wt.% Mn alloy in the form of as-cast ingots and cold rolled sheets has been investigated. It is shown that due to the formation of low alloyed aluminum solid solution and Al20Cu2Mn3 and Al3Zr (L12) phase nanoparticles, the 1.5MnCuZr alloy is superior to the base 1.5Mn alloy both in the hardness (up to two times) and electrical conductivity (up to 30%) after metal processing and annealing. A new alloy can be considered as a replacement for existing 6201 type conductive alloys.

High-Temperature Mechanical Properties of Aluminum Alloy Matrix Composites Reinforced with Zr and Ni Trialumnides Synthesized by In Situ Reaction

High-temperature strengths and stabilities of Al3Ni and Al3Zr phases can be used to develop heat-resistant Al-matrix composites. In the current study, Al-1Mg-0.8Mn-0.8V alloy matrix composites are synthesized by in-situ reaction of K2ZrF6 salt and Ni powder to yield Al3Zr- and Al3Ni-reinforcing phases. The as-cast microstructural and room-temperature and high-temperature tensile properties of the composite are investigated. The microstructure of the composites contain α-Al, Al3Zr, Al3Ni, and Al10V phases. The eutectic mixture comprises alternating Al3Ni and α-Al phases with fine Al3Zr precipitates distributed in the interlamellar regions. The (2 pct Al3Zr + 15.2 pct Al3Ni)/Al-alloy composite shows the highest mechanical properties at room temperature, with a tensile strength of 198 MPa and a fracture strain of 6.55 pct. At 200 and 300 °C, tensile strengths of (2 pct Al3Zr + 13.3 pct Al3Ni)/Al-alloy and (2 pct Al3Zr + 15.2 pct Al3Ni)/Al-alloy composites reach 175 MPa and 166 MPa, and 191 MPa and 155 MPa, respectively. At 350 °C, the highest tensile strength of this composite family reaches 82 MPa, which surpasses some of the existing Al-Si alloys used in automotive pistons, suggesting its potential high-temperature applications. Analysis indicates that the fracture mode of the present composites is ductile. Transgranular cleavage fracture of coarse, brittle Al10V phase, and microvoid coalescence are the main failure mechanisms.

Structure and Properties of Al-0.6%Zr-0.4%Fe-0.4%Si (wt.%) Wire Alloy Manufactured by Electromagnetic Casting

The experimental Al-0.6%Zr-0.4%Fe-0.4%Si alloy has been manufactured by using the method of electromagnetic casting. It is shown that Zr is completely dissolved in the aluminum solid solution (Al) and iron is fully included in the Al8Fe2Si phase. The fine microstructure of the as-cast rod implies a high deformation plasticity, which has been experimentally confirmed during wire production. The cold-rolled wire has an ultimate tensile strength (UTS) ~ 260 MPa, and subsequent annealing at 400°C for 3 h slightly reduces the strength, which is associated with the stabilizing effect of the L12 (Al3Zr) phase nanoparticles formed during annealing. Annealing also leads to a significant increase in the specific conductivity, the value of which reaches 57.0 IACS. Drawing of the annealed rolled wire leads to significant strengthening. Annealing at 400°C leads to a marked strength reduction, which, however, remains high enough for conductive alloys (UTS higher than 200 MPa).

Surface wear behavior and strengthening mechanism of Al3Zr particle reinforced aluminum matrix composites prepared in situ

Al3Zr+AA6082 particulate reinforced aluminum matrix composites were prepared in situ at 750 °C, 780 °C and 810 °C by the reaction of K2ZrF6 salt-coated powder with AA6082 melt under electromagnetic stirring. Linear friction and wear tests at room temperature were carried out on three kinds of Al matrix composites prepared at different temperatures. The test result were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), EDS, confocal laser scanning microscopy and transmission electron microscopy (TEM). The results show that the Al3Zr phase is formed at 750 °C, 780 °C and 810 °C and small. Under the same load, the wear volume of the composites prepared at 780 °C and 810 °C is larger than that of the aluminum matrix composites prepared at 750 °C. The main wear mechanisms of aluminum matrix composites prepared at various temperatures under different loads are adhesive wear, and the wear volume increases with the increase of load. The average friction coefficient of the three composites under different loads is about 0.5, and the friction performance is stable.

Improvement of corrosion penetration resistance for aluminum heat exchanger by alloying zirconium

Corrosion of the aluminum multi-port extrusion (MPE) leads to heat exchanger leakage. Corrosion of the 1xxx series aluminum MPE tubes proceeds continuously along Al13Fe4, which is the precipitation phase of Fe impurity. The continuous corrosion behavior along Al13Fe4 rapidly propagates into the aluminum MPE tube, thereby reducing the penetration life. In this study, Zr was added in order to control the dispersion of Al13Fe4 precipitates in an attempt to improve the corrosion resistance of A1070 aluminum MPE tubes for heat exchangers. The refinement and dispersion of Al13Fe4 phase was controlled by the addition of Zr, which is a highly insoluble element in aluminum. Zr plays a role in increasing nucleation and inhibiting the growth of the surrounding Al13Fe4 phase during the precipitation to Al3Zr phase. As a result, the size of the Al13Fe4 phase became finer and more dispersed, and the continuous corrosion tendency was decreased. Therefore, corrosion propagation of aluminum MPE tube progressed uniformly and penetration was suppressed.

Effect of Zr and Sc on microstructure and properties of 7136 aluminum alloy

We have linked experimental results to theoretical calculations and discussed the precipitation behavior of Zr and Sc in 7136 alloy and the influence of precipitation on the microstructure and mechanical properties of the alloy. The experimental results show that the added Sc atom can replace the Zr atom in the cubic Al3Zr phase with a lattice constant of a = 0.4417 nm, and form Al3(ScxZr1-x), which is also cubic and has a lattice constant of a = 0.4212 nm. A heterogeneous nucleation core promotes crystal-grain refinement, and the average size of the as-cast crystal grains is reduced from 82.4 μm to 51.7 μm. The valence electron structure and strongest bond energy of the Al3Zr phase with different structures was analyzed by the empirical electron theory. For Ll2-Al3Zr, the covalent electron number and bond energy of the strongest bonds are 0.3226 and 52.8 kJ/mol, respectively, and for DO23-Al3Zr, the numerical values are 0.4471 and 71.0 kJ/mol, respectively. Combined with the ab initio calculation, Ll2-Al3Zr has a good stability. Under suitable conditions, Ll2-Al3Zr will transform into the more stable DO23-Al3Zr. Quantitative analysis of the effect of strengthening mechanism such as fine grain strengthening and dispersion strengthening caused by the addition of Sc element on the yield strength of the alloy. The calculation results show that 0.2% elemental Sc addition can increase the alloy strength by 36.63 MPa, which is very similar to the measured result of 38.61 MPa.

Thickness-dependent Strengthening Effect of Grain Refiner Al3Zr and Al3(Zr,Sc) in Al Alloys

Grain refinement is an effective means to optimize the properties of the alloy. Al3Zr, Al3Sc and Al3(Zr,Sc) phases have attracted much attention as effective grain refiners for aluminum alloys, and their precipitation size will directly affect their interfacial strengthening effect with the matrix. In this paper, the first-principles method has been used to construct the Al/Al3Zr/Al double interface crystal model with different thicknesses of Al3Zr. The strengthening effect of the phase Al3Zr on the matrix during the precipitation growth process is described, and the optimal precipitation thickness of the strengthening phase Al3Zr is determined. By calculating the Griffith separation work and stress-strain curves of the interfaces between the refining phases with different thicknesses and the aluminum matrix, the change trend of the strengthening effect on the Al/Al3Zr/Al interface during Al3Zr precipitation growth is analyzed from the perspective of the combination of static and dynamic interface strength. Then the interfacial strengthening effect of the Sc-doped Al3(Zr,Sc) phase to Al matrix is analyzed. The electron density difference is used to analyze the interfacial bonding characteristics from the perspective of electronic bonding.

Effect of Rolling Process on Microstructure of 2A66 Al-Li Alloys Sheet

Influences of rolling process on microstructures of 2A66 Al-Li alloy thin sheet are investigated. Specimens with three different rolling processes and two heat treatments are taken into consideration. Results show that the passes of rolling process have a significant influence on Al-Li alloy textures. When the cold rolling reduction is 26%, there are some coarse particles identified as Al3Zr phase existing in the alloy and the anisotropy becomes obvious with low grain refinement. Under the cold rolling reduction 44.4%, the recrystallization grain increases and the grain refinement becomes better with the appearance of recrystallization, besides little lager grain. With a cold rolling of 48.7%, textures in alloy are better than 44.4% at homogeneity except the stratified phenomenon.

Interdiffusion and Reaction Between Al and Zr in the Temperature Range of 425 to 475 °C

Interdiffusion and reaction between Al and Zr was investigated as functions of Zr purity, temperature, and time, using Al versus Zr solid-to-solid diffusion couple annealed in the temperature range from 425 °C to 475 °C. All diffusion couples were observed to develop two intermetallic layers, i.e., Al3Zr and Al2Zr. The Al3Zr phase grew with planar morphology, while the Al2Zr phase developed a non-planar interfacial morphology. Growth rate and integrated interdiffusion coefficients were determined using Wagner’s approach for each phase. Purity of Zr had a significant effect on the development of Al3Zr and Al2Zr phases. Diffusion couples with low-purity Zr (i.e., 99.2%) exhibited a higher growth rate for the Al3Zr, at the expense of Al2Zr growth. Couples with low purity Zr also resulted in a higher degree of non-planarity for Al2Zr phase. In general, degree of non-planarity increased with an increase in anneal time, while it decreased with an increase in temperature. Non-planar morphology was simulated based on 3-D anisotropic diffusion using diffusivity tensor (quadric), and needle-like growth, similar to that observed by experiments were simulated.

High-temperature properties and microstructural evolution of Al–Cu–Mn-RE (La/Ce) alloy designed through thermodynamic calculation

A theory guide method based on thermodynamic calculation and experimental verification is performed on the composition optimization and heat treatment process of heat-resistant Al–Cu–Mn-RE(La/Ce) alloys. Al-5.0Cu-0.6Mn-1.5RE(La/Ce) is obtained to be the reasonable alloy composition for further investigation. The strength of heat treatment state alloy decreases 20–33 MPa as the temperature rises every 50 °C in the high temperature tensile experiments. The alloy has good heat resistance, with high temperature (300 °C) strength of 102.4 MPa. The high temperature fracture mode is a mixed forms of brittle and ductile fracture. Heat exposure temperature has a significant effect on both thermal and electrical conductivity, by influencing the morphology and distribution of heat-resistant phases. With the increase of heat exposure temperature, the tensile strength of the alloy firstly increases and then decreases. With heat exposure at 200 °C or 350 °C for 100 h, the room temperature tensile strength values are 232.77 MPa or 190.52 MPa, respectively, which indicates that the alloy has good high-temperature durable performance. The nano-sized Al2Cu phase, T phase and Al3Zr phase exist in the heat treatment state alloy, and result in good heat resistance. Heat exposure at 300 °C for 100 h leads to the growth of Al2Cu phase and close distribution of heat-resistant phase Al3Zr around the Al2Cu phase. Presence of eutectic phase hinders the dislocation movement and thus improves the resistance to deformation at high temperature.

Effect of Transition Metals Addition on the Microstructure and Incipient Melting of 354-Based Alloys

Thermal analysis of various 354 alloy melts was carried out to determine the sequence of reactions and phases formed during solidification under close-to-equilibrium cooling conditions. The main reactions observed comprised formation of the α-Al dendritic network at 598 °C followed by precipitation of the Al–Si eutectic and post-eutectic β-Al5FeSi phase at 560 °C; Mg2Si phase and transformation of the β-phase into π-Al8Mg3FeSi6 phase at 540 °C and 525 °C; and lastly, precipitation of Al2Cu and Q-Al5Mg8Cu2Si6 at 498 °C and 488 °C. As a result of the low solidification rate of the thermal analysis castings, all Zr-containing alloys are located in the L + Al3Zr region of the Al–Zr phase diagram during the melting stage. Three main reactions are detected with the addition of Ni, i.e., the formation of AlFeNi, AlCuNi and AlSiNiZr phases. Larger sizes of AlFeNi and AlCuNi phase particles were observed in higher Ni content alloys of 3.6 wt%. Mn addition helps in reducing the detrimental effects of the β-iron phase by replacing it with the less-detrimental Chinese script α-Al15(Fe,Mn)3Si2 phase and sludge particles. With the use of the multi-step solution treatment—involving higher solution temperatures and longer durations, an increased amount of incipient melting is likely to occur.

Structural evolution of Al-modified PS-PVD 7YSZ TBCs in thermal cycling

Feather-like columnar 7YSZ thermal barrier coatings (TBCs) were prepared by plasma spray-physical vapor deposition (PS-PVD). In order to improve the thermal cycle performance of TBCs, Al-modification was carried out with the as-sprayed TBCs. Al film was deposited on the surface of TBCs. Subsequently, the Al-deposited TBCs were conducted with vacuum heat treatment. After that, a dense overlay consisting of α-Al2O3, Al3Zr phases was generated on the TBCs surface due to the reactions of Al and O2, Al and ZrO2. The Al-modified TBCs show a better thermal cycle performance than the as-sprayed TBCs because of the overlay generation. Moreover, the structural evolution of overlay was investigated emphatically before and after thermal cycle testing, showing good phase stability. No crack and spallation were observed in the Al-modified TBCs.

High-Temperature Synthesis of Al–Zr–W Aluminum-Matrix Alloys

This paper reports the preparation of Al–Zr–W aluminum-matrix alloys containing reinforcing inclusions of various phases. The alloys have been produced by the aluminothermic reduction of starting mixtures consisting of zirconium and tungsten oxides in the first stage and of baddeleyite and scheelite mineral concentrates in a second stage. According to our experimental data, the use of baddeleyite and scheelite instead of zirconium and tungsten oxides in the starting mixture produces no significant changes in the elemental composition of the alloy: the total zirconium and tungsten content of the alloy is 31–32 wt %. Characterization of the alloy prepared using the mineral concentrates has shown that the aluminum matrix contains inclusions of the Al3Zr and Al4W intermetallic phases and a small amount of the ZrN nitride. The volume fraction of the inclusions in the alloy is 32–38%. Most of the structural constituents of the alloy contain a small amount of unwanted silicon and iron impurities (~3%), which originate from the mineral concentrates. In the future, to reduce the impurity concentration we plan to use technological approaches that will ensure preliminary purification of mineral concentrates.

Influence of Molybdenum, Zircon and Copper on Structure of Aluminum Alloy AlSi10Mg(Cu) (En Ac-43200)

The paper deals with the influence of molybdenum, zirconia and cobalt on the AlSi10Mg (Cu) alloy microstructure. The work methodology was focused on the analysis of phases morphology for material alloyed with Mo, Zr and Co. Molybdenum in the AlSi10MgCu alloy creates phases with skeletal morphology bounded on iron phases Al(Fe, Mn, Mo)Si. Used heat treatment has softened these phases and is a prerequisite for increasing the strength characteristics and hardness. By alloying the alloy with zirconium to isolate Al3Zr phases, which represent a strong nucleation potential for α-Al. It has been confirmed that Al3Zr particles do not tend to interact with other elements. The results of experiments show that cobalt affects the morphology of iron phases. The findings of this study can provide further insight into the transition metals in Al-Si-Mg-Cu alloys and the potential for developing a new generation of heat-resistant alloys based on Al-Si.