Zr Alloy Powders Research Articles

Study on Microstructure and Properties of Cu-Zr Alloy Prepared by Mechanical Alloying

In this paper, Cu-Zr alloy powders and materials with different Zr contents were prepared by horizontal stirring high-energy ball milling combined with vacuum hot-pressing sintering. The results show that the mechanical alloying time of Cu-5%Zr, Cu-10%Zr and Cu-15%Zr alloy powder prepared by high energy ball mill is 7 h, 14 h and 22 h, respectively. At the beginning of high-energy ball milling, Zr particles adhere to the Cu matrix and agglomerate phenomenon occurs. With the progress of ball milling, the powder particles become smaller, the Zr particles gradually distribute evenly and widely on the surface of the Cu matrix, and are dissolved in the Cu matrix, and finally alloying is achieved. Cu-Zr alloys with different Zr content are prepared by vacuum hot pressing sintering. When Zr content is 10%, the maximum hardness of Cu-Zr alloy is 277.24HV, which is 462% higher than that of pure copper.

Selective Laser Melting of Gas Atomized Al–3.02Mg–0.2Sc–0.1Zr Alloy Powder: Microstructure and Mechanical Properties

Additive manufactured Sc modified Al alloys for lightweight application is now arousing widespread attraction. The selective laser melting (SLM) of gas atomized Al–3.02Mg–0.2Sc–0.1Zr powder is studied, with the emphasis on its densification, microstructure, and properties. The intrigued finding is that the very high elongation‐to‐failure of 32.5% is obtained with medium tensile strength of 373 MPa after heat treatment of SLM sample. The average relative density is about 98.3% at a volumetric energy density range of (VED) 42–111 J mm−3. The microstructure of produced sample shows cracks but it can be inhibited by increasing the VED. At an excessive VED, the weld pool is transformed from heat conduction to keyhole mode owing to the metal evaporation. Nano‐sized Al3(Sc,Zr) precipitates with a diameter of 5–50 nm are observed, which is responsible for the main strengthening mechanism. The underlying mechanisms of metallurgical defects, weld pool mode and mechanical properties are also illuminated.

Extrusion of Al-Si alloy compacts under conventional conditions and in the semi-solid state

.In this research work the results of hot extrusion process of aluminium alloy compacts conducted at the temperature of conventional hot extrusion as well as at the temperature range corresponding to the semi-solid state were presented. Initial material was prepared by uniaxial pressing of Al17Si5Fe3Cu1.1Mg0.6Zr alloy powder. The extrusion process was carried out under isothermal conditions, and the temperature stability was strictly controlled. The changes of extrusion force in relation to punch displacement were recorded during hot deformation to demonstrate the effects associated with the appearance of the liquid phase in the volume of the processed material. After extrusion the samples were cooled in water as well as at room temperature. The influence of temperature of extrusion and the resulting fraction of the liquid phase in the processed material on its microstructure and chosen mechanical properties were determined. Mechanical properties of the examined alloy after deformation were carried out by measuring the hardness and in uniaxial compression tests. Additionally, one of the compacts was remelted and cast, what made possible comparison of the microstructure and chosen properties of the obtained products. In the result of the investigations it has been proved, that extrusion in semi-sold state results in reduction of forces necessary to complete deformation process and leads to obtaining the material with good mechanical properties and fine-grained, favourable microstructure.

Nano ZrO2 particles in nanocrystalline Fe–14Cr–1.5Zr alloy powders

Here we report on the formation of nano ZrO2 particles in Fe–14Cr–1.5Zr alloy powders synthesized by mechanical alloying. The nano ZrO2 particles were found uniformly dispersed in the ferritic matrix powders with an average size of about 3.7nm, which rendered the alloy powders so stable that it retained nanocrystalline structure after annealing at 900°C for 1h. The ZrO2 nanoparticles have a tetragonal crystal structure and the following orientation relationship with the matrix: (002)ZrO2//(002)Matrix and [010]ZrO2//[120]Matrix. The size and dispersion of the ZrO2 particles are comparable to those of Y–Ti–O enriched oxides reported in irradiation-resistant ODS alloys. This suggests a potential application of the new alloy powders for nuclear energy applications.

Fabrication and characterization of nanocrystalline Nb–W–Mo–Zr alloy powder by ball milling

A superfine nanocrystalline Nb–W–Mo–Zr alloy powder was successfully prepared by high energy ball milling at room temperature. The particle size, morphology, and structural changes were characterized by means of laser particle size analysis (LPSA), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Experimental results showed that milling velocity was a decisive factor in controlling the production of alloy powders. A 450rpm-ball milling had led to nanocrystalline Nb–W–Mo–Zr alloy powder particles with a crystallite size of 14nm. With 250rpm velocity, cold welding was found to be the dominant mechanism during milling without formation of any solid solution even after 60h of milling time.

INFLUENCE OF CLOSED-DIE HOT COMPACTION PARAMETERS ON SELECTED PROPERTIES OF PM AL-SI-FE-CU MATERIALS

The work presents the results of investigations of the materials obtained by closed-die hot compaction of A117Si5Fe3Cu1.1Mg0.6Zr alloy powder. The influence of temperature and punch unit pressure on the shape of samples, as well as on relative density, selected mechanical properties and microstructure of obtained products, was estimated. The beneficial parameters of hot compaction were determined.

High temperature properties of Cu–Cr–Zr alloys processed by conventional inverse extrusion of atomised powders and comparison with Conform consolidated powders

Water atomised Cu–Cr–Zr alloy powders were consolidated by inverse warm extrusion and by the commercial continuous rotary extrusion method, Conform. Those alloys consolidated by inverse warm extrusion exhibited enhanced mechanical properties compared with their respective Conform extruded counterparts, when tested at both room and elevated temperatures. The processing parameters adopted in the inverse extrusion experiments resulted in products which retained enough amounts of solutes in solid solution, which in turn, led to improved mechanical properties after aging. Conversely, the excessive adiabatic heat generated in the Conform machine eliminated the saturation effect produced by rapid solidification, negating any possible further improvement on the mechanical properties by aging. The mechanical properties of an inverse extruded Cu–2.8Cr–0.39Zr (at.-%) alloy at temperatures above 450°C were higher than those strengths reported for Cu–Be alloys and comparable to that of Cu–Ta and Cu–Nb composites. Therefore, rapidly solidified Cu–Cr–Zr alloys can be possible candidates for replacing such alloy systems for high temperature applications.

Vacuum degassing behavior of rapidly solidified Al–Mn–Zr alloy powders

Gas desorption behavior and surface change characteristics of Al–Mn–Zr, Al–Mn, and Al–Zr alloy powders with heating in vacuo have been investigated by temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS) measurements. TPD measurements on powders exposed to humid air, dry air, and high purity argon gas were performed to determine the gas species evolved during degassing of Al alloy powders. The alloy composition and P/M processing atmosphere had a strong influence on degassing behavior. The surface oxides of Al alloy powders containing Mn and/or Zr were prone to hydration. Thus, the formation of fresh Al 2O 3 on the Al alloy powders occurred at low temperature during vacuum degassing by the reaction, Al + 3H 2O = Al 2O 3 + 3H 2. High-temperature XPS showed that decomposition of the hydroxide into oxide on the Al–Mn–Zr alloys occurred at 623 K.

Strengthening in rapidly solidified age hardened CuCr and CuCrZr alloys

CuCr and CuCrZr alloy powders were produced by water atomization and consolidated by warm extrusion. Coherent Cr precipitation is associated with the peak hardness condition in these alloys. The mechanical properties obtained after ageing treatments, namely the peak hardness, and the corresponding proof stress are related to the concentration of the alloying element initially in solid solution in the powders. The strengthening observed is interpreted in terms of theories of precipitation and dispersion strengthening and compared with similar analyses reported previously in the literature for these alloy systems.

Characteristics of Al–Cr–Zr alloy powders made by confined nozzle atomisation

The effects of superheat and powder particle size fraction on the characteristics of Al–5Cr–2Zr (wt-%) alloy confined nozzle atomised powder particulate has been investigated. The median powder particle size decreased from 62 to 38 μm with increase in superheat from 140 to 300 K for the atomising conditions studied, with a broadening of the size distribution and the increasing presence of large irregular powder particles at the lowest superheats. Essentially featureless α-Al based microstructures in splat caps and small sized powder particles were replaced by cellular α-Al with increasing amounts and sizes of primary L12Al3Zr and Al13Cr2 inclusions with increasing powder particle size. Refinement of the α-Al cell and intermetallic inclusion sizes in a fine compared with a coarse powder size fraction was consistent with the expected powder relationship between these variables. The decreased microhardness for coarser powder particle size fractions was attributed to the formation of increasingly coarse distributions of the primary aluminides at the expense of retention of Zr and Cr in extended solid solution. A notable age hardening response after 1h at 350–450°C for the 25–50 μm powder size fraction was consistent, however, with retention of 0·5–1·0 wt-%Zr in solid solution in this fine size fraction of the powder.MST/3163

Characteristics of Al–Cr–Zr alloy powders made by confined nozzle atomisation

Characteristics of Al–Cr–Zr alloy powders made by confined nozzle atomisation

Inert Gas Atomised Al–Cr–Zr Alloy Powders Consolidated by Extrusion: Effect of Powder Variables and Extrusion Parameters on Extrusion Pressure

The effect on extrusion pressure P of ram speed V (0·5–4 mm s−1), extrusion ratio R (14:1−28:1), extrusion temperature T (300−450°C), median powder particle diameter (11−141 μm), and melt superheat during atomisation (150−300 K) has been studied for extrusion of argon atomised Al–5Cr–2Zr (wt-%) alloy powder. Mean powder particle size and T had the major influence on P; R and V had less influence and melt superheat during atomisation had no influence. The absence of a breakthrough pressure, attributed to the low values of V used, allowed extrusion at values of T as low as 300°C, retaining the integrity of the rapidly solidified microstructure. The relative importance of work of consolidation compared to that of homogeneous deformation, as demonstrated by a value of 4·6 for the ratio a/b in the equation P = a + b ln R at 350°C, was larger than reported for 7090 and 7091 alloys but smaller than for Al–2·4Fe (wt-%) at a comparable T. The magnitude of the temperature dependence of P was similar to that reported for other high strength aluminium alloy powders, the corresponding dependence for consolidation pressure being significantly lower. PM/0683

Shock consolidation of AlLi alloy powders

Several rapidly solidified AlLi-based alloy powders were successfully consolidated into crack-free compacts by explosively generated shock waves. Both flyer plate and direct contact techniques were applied in cylindrical and plate configurations. Densities of the compacted powders reach over 97% of their theoretical values. The microstructures of the compacts were evaluated by optical and electron microscopy. Crack-free compacts were produced by using the flyer tube technique in the cylindrical separated by random stacking faults or several atomic layers of f.c.c. structure. A high density of hot-extruded alloys. Compacts of Al3wt.%Li1wt.%Cu1wt.%Mg0.2wt.%Zr alloy powders exhibited the highest tensile strength (282 MPa). The optical micrographs showed that the crack-free compacts had considerable interparticle melting. The interparticle melting regions were analyzed by X-ray diffraction and transmission electron microscopy and had a microcrystalline structure with precipitates of δ′-Al 3Li and δ-AlLi. Fractographs of tensile specimens revealed that the compacts having high tensile strength had strong interparticle bonding; their rupture surface exhibited transparticle fracture.

Laboratory Produced P/M Aluminum 2XXX + Zr Sheet

Laboratory procedures were established to produce advanced aluminum 2XXX+ Zr alloy powder metallurgy sheet in the T8X temper. The sheet was tested for tensile and Kahn Tear properties in the longitudinal and long transverse directions. The results from the laboratory-produced sheet were compared to the results of a pilot-scale NASA contractual study which used the same alloy powders, leading to the conclusion that laboratory-scale sheet properties are good to excellent predictors of the pilot-scale tensile properties and tear notch toughness values. Tear resistance toughness at pilot scale was not satisfactorily predicted by the laboratory results.