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This work aimed to study the microstructural evolution of commercial aluminum alloy AA7050 in the solution treated condition (W) processed by equal channel angular pressing - ECAP. The analyses were made considering the effects of process parameters as temperature (Tamb and 150°C), processing route (A and B C) and number of passes. Optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used for microstructural characterization, and hardness tests for a preliminary assessment of mechanical properties. The results show that the refining of the microstructure by ECAP occurred by the formation of deformation bands, with the formation of dislocations cells and subgrains within these bands. The increase of the ECAP temperature led to the formation of more defined subgrains contours and intense precipitation of η phase in the form of spherical particles. The samples processed by Route B C present a more refined microstructure.

Despite, the homogeneous and refined microstructure, spray-formed deposits of binary Fe–Si alloys with high silicon content are still difficult to hot/cold roll due to A2-disordered/B2-ordered reactions. The addition of aluminum to Fe–Si alloys may be able to keep the A2-disordered phase metastable at temperatures below 973 K, allowing the deposits to be rolled without cracking while adequately maintaining their magnetic properties. This study is a first attempt to investigate the microstructure and the magnetic properties of spray-formed Fe–3 wt.%Si–3.5 wt.%Al alloy. Argon and nitrogen were used as atomization gases. The addition of aluminum to Fe–Si alloys led to the successful production of thin sheets (0.5 mm thickness) from spray-formed deposits when using argon as atomizing gas. In contrast, the use of nitrogen led to the formation of AlN particles, resulting in excessive brittleness of the spray-formed deposit, which fractured during cooling to room temperature. Otherwise, the magnetic properties of the Fe–3.0 wt.%Si–3.5 wt.%Al alloy performed very well when compared with binary Fe–6.5 wt.%Si, especially when spray formed with argon.

The microstructure and the tensile properties of an spray co-deposited Al-8.9 wt.% Si-3.2 wt.% Cu-0.9 wt.% Fe + (Al-3 wt.% Mn-4 wt.% Si)p composite was investigated after extrusion and heat treatment. The composition of the AlMnSi p alloy was selected aiming to improve the formation of α-Al(Fe,Mn)Si instead of β-Al(Fe,Mn)Si intermetallic. The spray formed deposits were extruded at 623 K and heat treated to peak aged (T6) condition. Room temperature tensile tests of the spray formed and extruded/heat treated alloy showed significant increase of elongation to fracture when compared with the values observed for the as-spray formed deposits, >10% and

The present work reports the development of bulk fine structured AlFeNd and AlFeNdCuSi alloys processed directly from the liquid, using a new centrifugal force casting method. The casting equipment consists of a device adapted in a single roller melt spinning that converts the vertical turn of the melt spinning in a centrifugal force that presses the liquid alloy into a copper mould. The basic details of the device and a first model for the liquid movement are described. Microstructures, hardness and compressive strength results are also presented. The results are compared to the same alloys cast through gravity mould casting. It is shown that the new method promotes finer microstructures and considerably superior mechanical properties. The AlFeNd centrifugal cast specimens lead to higher compressive strain and strength, comparable to high strength wrought conventional Al alloys.

In this study the Fe63Nb10Al4Si3B20 (at.%) alloy was processed by spray forming with the aim of investigate the formation of amorphous phases and novel microstructures by the high cooling rate involved in this process. The gas/metal mass flow rate used was 0.25, and nitrogen was used as the atomization gas. The resulting deposit of a mass of about 1.2 kg, as well as the overspray powder, with a median particle diameter about 120 μm, were characterized by using X-ray diffractometry, differential scanning calorimetry and scanning and transmission electron microscopy with energy of dispersive spectroscopy. Magnetic properties were measured through hysteresis loop tracer equipment. The overspray powder presented a mass median diameter of d50 ≅ 120 μm and an increasing of amorphous phase volume fraction with decreasing of particle size. The microstructure of the deposit was heterogeneous varying with the thickness, presenting at center region 20 mm and at border 1 mm with different porosities 5 and 10%, respectively. The thicker region presented fully crystalline microstructure whereas the thinner presented about 75% amorphous phase. The phases identified in both deposit and overspray powder were: amorphous, α-Fe, Fe23B6, FeB and FeNbB. Amorphous phase formation in the thinner region of the deposit and the absence in the thicker region indicates that the resulting amorphous phase depend on the maintenance of amorphous phase formed during atomization that might be controlled by process parameters. Spray forming of Fe-based amorphous alloys followed by hot consolidation in T

Aluminum additions to brittle Fe–6.5 wt.% Si alloys made possible the mechanical processing of these alloys at lower temperatures and thus being determinant in the development of the texture. The aim of this work was to analyse the evolution of the crystallographic texture of a spray-formed (SF) Fe–6.5 wt.% Si–1.0 wt.% Al during rolling operation for thin sheets production. The SF deposit was warm-rolled and then air cooled to obtain partial recrystallisation. The initial texture (0 1 1) [ 0 1 ¯ 1 ] [1 0 0] (// to normal direction-ND) of the deposit was changed to approximately (0 1 3) [ 1 1 ¯ 0 ] [1 1 0] (8° from ND) after the last reduction step. The maxima intensities of texture was found at 700 °C (89% of reduction) showing the influence of rolling temperature; after warm-rolling the entire texture changes to a partial ND fibre running from {0 0 1} to {1 1 0}, with negligible Goss intensities. The transition away from an ND fibre texture in the lattermost case (99.5% reduction) was in turn associated with the near-absence of shear bands.

In the present work Fe 73− x Nb x Al 4 Si 3 B 20 ( x = 5, 10) alloys have been processed by melt-spinning with the aim of studying the crystallization sequence through annealing in suitable temperatures. Melt-spun ribbons were characterized by differential scanning calorimetry (DSC), X-ray diffractometry (XRD) through Cu-Kα ( λ = 1.54 A) and synchrotron radiation ( λ = 1.77 A) and transmission electron microscopy (TEM). Soft magnetic properties were measured through the hysteresis loop tracer. In-situ XRD through synchrotron radiation was very accurate in phase identification. Fe 73− x Nb x Al 4 Si 3 B 20 ( x = 5, 10) alloys showed the possibility of forming ferromagnetic amorphous alloys composed of commercial Fe-based master alloys with fine nanocrystalline structure and good soft magnetic properties.

The sliding wear resistance of high-chromium white cast iron obtained by spray-forming was studied to determine how the refined microstructures produced by this process, the structure of the matrix, and the amount and distribution of carbides affect the material. Three alloys containing different concentrations of carbon and chromium, namely 2.4 wt.%C–15 wt.%Cr, 3.5 wt.%C–15 wt.%Cr, and 3 wt.%C–19 wt.%Cr, were spray-formed and conventionally cast. Pin-on-disk wear tests were conducted according to the ASTM G99-95 standard. White cast iron pins having an 8-mm diameter and 15-mm length were tested against a counterpart VC 131 tool steel disk hardened to 63HRC. The wear resistance was evaluated as a function of the samples’ weight loss and the wear mechanisms were observed by scanning electron microscopy (SEM). These wear mechanisms, which were active in all the materials, were fracture and detachment of carbides and oxidation, which suggests three-body abrasion, in addition to the presence of cracks in the matrix, particularly in the materials containing large amounts of austenite. Disk wear rates were found to be higher than high-chromium white cast iron pin wear rates. These wear rates were more pronounced when the disks were tested against the conventionally cast pins, which showed coarser carbides. The spray-formed alloy, 3.0 wt.%C–19.0 wt.%Cr, showed better wear resistance in this study than the other alloys because of its more refined microstructure, greater balance among the austenite, martensite and M 7 C 3 carbide phases, and greater resistance to oxidation.

The utilization of Mg in hydrogen storage applications has been hindered by its high sorption temperature and slow kinetics. Both nanocrystallization and addition of transition metal catalysts demonstrated to improve the hydrogen sorption kinetics of Mg. In this scenario, high energy ball milling has shown to be a suitable way for processing Mg based nanostructured material, especially when milling is carried out under a hydrogen atmosphere (reactive milling, RM), which provides a nanostructured and hydrogenated final product. In the present work, we investigated the structural evolution of Mg, Nb and a mixture of Mg–5 at.%Nb processed by reactive milling by using the X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. The dehydrogenation behavior was investigated by differential scanning calorimetry (DSC) and the hydrogen content measured using a Leco determinator. It was found that Nb rapidly absorbs hydrogen, forming the NbH0.9 phase. On the other hand, Mg was only partially transformed into β-MgH2 and γ-MgH2 phases. The amount of non-reacted Mg apparently does not vary when the milling time increases from 25 to 48 h. When Mg–5 at.%Nb mixture was milled for 48 h, almost all Mg and Nb were transformed into hydrides. Only a small amount of non-reacted Mg still remained in the sample. This result clearly shows the catalytic effect of Nb on the hydrogen sorption of Mg. Another remarkable feature observed is that Mg also contributed for the Nb hydrogenation as the NbH2 phase was detected in the composite, which does not happen when pure Nb was milled in the same conditions. The structural evolution of the Mg–Nb composite is discussed based on the results obtained when the milling time is increased and comparing these results with those obtained for the pure elements. The DSC thermograms revealed that both Mg and Mg–Nb samples presented lower dehydrogenation temperatures when compared with the polycrystalline Mg. The Mg–Nb nanocomposite showed the lowest desorption temperature (270 °C) and fastest kinetics of hydrogen sorption.

The glass former Fe 83 Zr 3.5 Nb 3.5 B 9 Cu 1 (at.%) alloy was processed by spray forming. The aim was to investigate the possibility of forming novel microstructures using this process. The ratio between the gas mass flow rate and the metal mass flow rate used was 0.23, and nitrogen was used as atomization gas. The resulting deposit, weighting about 0.8 kg, as well as the overspray powder with a median particle diameter about 150 μm, were characterized by using X-ray diffratometry, differential scanning calorimetry and scanning electron microscopy with energy dispersive spectroscopy. Saturation induction ( B s ), maximum permeability ( μ max ) and coercive field ( H c ) were measured. The overspray powder showed a microstructure consisting of amorphous and α-Fe phases. The volume fraction of the amorphous phase decreased as the granulometric size range increased. The deposit presented fully crystalline structure with α-Fe, Fe 3 Nb, Fe 2 Zr and Fe 2 B phases. The formation of amorphous phase in the overspray and its absence in the deposit indicates that the deposit was formed by the impacting of a high volume fraction of fully liquid droplets, providing temperature and time enough for complete crystallization of the deposit.

The microstructure and the tensile properties of an Al–8.9 wt.% Si–3.2 wt.% Cu–0.9 wt.% Fe–0.8% Zn alloy processed by spray forming was investigated. The alloy was gas atomized with argon and deposited onto a copper substrate. The microstructure was evaluated by optical microscopy (OM), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Small faceted dispersoids observed surrounding equiaxial α-Al matrix were identified by SEM–EDS as silicon particles. Sand cast samples with the same composition showed a columnar dendritic α-Al matrix, Al–Si eutectic, polyhedric α-AlFeSi and needle-like β-AlFeSi intermetallics. In the spray formed material the formation of the Al–Si eutetic was suppressed, and the formation of the α-AlFeSi and β-AlFeSi intermetallics was strongly reduced. The fine and homogeneous microstructure showed an aluminium matrix with grain size ranging from 30 to 40 μm, and particle size of the silicon dispersoids having a mean size of 12 μm. Room temperature tensile tests of the spray formed alloy showed relative increasing of strength and elongation when compared with the values observed for the conventionally cast counterparts. These results can be ascribed to the refined microstructure and the scarce presence of intermetallics of the spray formed material.

The microstructures and properties of Al-based alloys produced by severe plastic deformation under high pressure torsion straining were compared with alloys of the same compositions consolidated by hot extrusion and spray-forming processing. Partially amorphous alloy powders of two systems were studied; Al 90 Fe 7 Z 3 alloy powders were prepared by high-energy ball milling and Al 84 Y 3 Ni 8 Co 4 Zr 1 +SiC composite powder was prepared by gas atomisation. The alloy powders have been cold consolidated by high-pressure torsion straining under a stress of 5 GPa resulting in refined and uniform microstructures, with hardness values well above the measured values for the hot-extruded Al 90 Fe 7 Z 3 alloy and for the spray-deposited Al 84 Y 3 Ni 8 Co 4 Zr 1 +SiC composite alloy.

Reactive high-energy milling can lead to self-sustaining reactions in the synthesis of a variety of systems, with the reaction being observed after an induction or ignition time which produces a temperature increase in the reactants. The products of such reactions are usually very strong agglomerates which, would be not very useful for further processing; to obtain fully dense sintered samples, it would be necessary an additional and difficult desagglomeration procedure. Therefore, the knowledge and control of the mechanism during reactive high-energy milling may be important in preventing or reducing this agglomeration and improve the physical properties of the powder reaction products. In the present work, high-energy ball milling of the powder mixture Nb2O5–Al–C was performed in a SPEX 8000 shaker/mill. The reaction was monitored by a thermocouple fixed in the external surface of the vial. With the condition of ball to mass ratio of 4:1 ignition occurs after 190 min milling. Powder mixtures were characterized after different milling times before and after the reaction. Also, alumina powder was added as diluent to the reactant mixture aiming to decrease the reaction temperature. The powders were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). The reaction products after 1 h were desagglomerated and mixed with commercial ultra-fine alumina powder, producing alumina matrix nanocomposites with 5 wt.% of NbC. © 2003 Elsevier Science B.V. All rights reserved.

Powders of titanium, silicon and carbon black with a molar ratio of 3:1:2 were milled in a high-energy ball mill in order to produce titanium silicon carbide (Ti3SiC2). The milling process initiated an exothermic reaction and the starting material was completely converted into a mixture of mainly titanium carbide (TiC) and minor amounts of TiSi2 ,T i 5Si3Cx and Ti3SiC2. Using off-stoichiometric mixtures or SiC as a source of silicon did not affect the amount of TiC in the product. To obtain Ti3SiC2 the as-milled powders were pressed to compacts and sintered for 2 h. The thermal treatment caused the formation of large amounts of Ti3SiC2. Using a slight excess of silicon in the range of 10–30%, pure samples of the ternary phase could be obtained. © 2002 Elsevier Science B.V. All rights reserved.

In the present work the Zr 55 Al 10 Ni 5 Cu 30 alloy has been processed by melt spinning and die-casting into a chilled copper mold. The ribbon was fully amorphous (X-ray diffraction and transmission electron microscopy) and cast samples partially crystalline. The amorphous ribbon was crystallized and analyzed by differential scanning calorimetry, X-ray diffractometry and transmission electron microscopy. The smaller supercooled liquid range of the glassy ribbons (60 K) and partial crystallization of a larger cast sample during quenching indicate the presence of oxygen in both samples (∼0.8 at.%). Although the crystallization process of the glassy ribbon, a glass transition followed by a single crystallization peak, showed the same crystallization process as reported by the literature, the heat release and the phases formed differed. The main phases formed were Zr 2 Cu, a complex `big-cube' fcc Zr 4 Cu 2 O-type phase and a tetragonal phase, not reported before to our knowledge, containing a lattice parameter of 2.8 nm.

Bulkmetallicglasses(MGs)arecurrentlysubjectofintenseresearchduetotheiruniquemechanicalproperties:NewtonianviscousformabilitybetweentheglasstransitiontemperatureT g andcrystallisationtemperatureT x andelasticstrainrangeofwellover1%belowT g .However,someMGsarebrittle.Fe-basedMGsandsomeothersarepronetothermalembrittlementevenduringthequench.CompositionaladjustmentsinthedesignofFeB-basedalloyshaveallowedpreparationofmetalloidpoorFe 40 Co 5 Ni 35 Zr 5 B 15 thathasc-Feasaprimarycrystallisationproductforob-tainingductilityofmetallicglass-matrixtoughenedbyc-Fecrystallisation.Structuralcharacterisationusingdiffractionofhighenergysynchrotronlight,transmissionelectronmicroscopy,scanningelectronmicroscopyarepresentedtogetherwithhardnessandweardata. 2002ElsevierScienceB.V.Allrightsreserved. 1.IntroductionDuetotheirnearly2%elasticstrainrange(ascomparedto0.2%forcrystallinematerials),me-tallicglasses(MGs)currentlyhavethebestknownAshbyperformanceindexr 2 =E (wherer andEaretheyieldstrengthandYoung’smodulusrespec-tively).Largerindicesofthisperformanceindexforsprings(reversiblestoringofelasticenergy)minimisevolume.Inadditiontometallichardnessandtoughness,someMGshavetheformabilityofpolymersintheirsupercooledliquidtemperaturerangebetweentheglasstransition,T

We have used severe plastic deformation (high-pressure torsion straining) to achieve cold consolidation of gas-atomised Al 90 Fe 5 Nd 5 powders into bulk nanostructured disks with a dispersion of fcc-aluminium crystallites within the glassy matrix with full density and hardness in excess of 3 GPa. The micro- and nanostructure of the resulting disks is presented.

The crystallization behavior and microstructure development upon annealing amorphous Al84Y9Ni5Co2 melt-spun ribbons have been investigated by a combination of differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and X-ray diffraction (XRD). Crystallization is shown to occur in three stages: (1) primary crystallization of α-Al; (2) formation of an unknown crystalline phase; (3) formation of Al3Y, Al9Co2 and a phase similar to Al16Ni3Y. The morphology, EDS and diffraction patterns indicated that the two unknown phases, from the second and third stages, are different phases and both are quaternary compounds.

In this work the easy-glass-forming amorphous alloy Zr 55 Al 10 Ni 5 Cu 30 was obtained by the melt-spinning technique in the shape of ribbons. Two kinds of ribbons were produced, one with the pure alloy and another one with 1 wt.% of lanthanum oxide particles introduced in the molten alloy. Both ribbons were fully amorphous, according to X-ray diffraction; the inoculated amorphous ribbon was also analysed by scanning electron microscopy. Samples were cut from these amorphous ribbons and crystallised in a differential scanning calorimeter. No changes was observed in the glass transition temperature ( T g ) or in the crystallisation on set temperature ( T x ), and thus in the glass forming ability. The crystallisation products were analysed by X-ray diffraction and transmission electron microscopy. The pure alloy ribbon showed the presence of CuZr 2 and Al 3 Zr 4 stable phases plus a metastable phase. The inoculated crystallised ribbon on the other hand showed mainly the presence of the metastable phase plus a quasicrystalline phase which was not observed in the crystallised pure alloy. Thus the presence of lanthanum oxide drastically changed the phase selection for crystallisation.

Amorphous Fe‐M‐B (M‚Zr, Nb) based alloys with nanometer-sized crystallites have attracted attention due to their magnetic properties. Although corrosion resistance is a desirable property in such alloys, no study concerning this aspect has been reported. The eAect of metalloid content and partial crystallization on corrosion resistance of Fe‐M‐B (M‚Zr, Nb) amorphous alloys, Fe84Nb7B9 ,F e 84Zr7B9 and Fe83Zr3:5Nb3:5B9Cu1, was investigated. Corrosion resistance measurements were carried out by mass loss, potentiodynamic polarization, and thermogravimetric mass gain measurements. The partial crystallization of the amorphous alloy results in a decrease of the corrosion resistance for all the compositions analyzed. We also observed a greater corrosion resistance when Nb was present in comparison to the case when Zr was present. These results are an eAect of the superficial passive film protector formed. ” 2000 Published by Elsevier Science B.V. All rights reserved.

An Fe 73.5 Si 15.5 B 7 Nb 3 Cu 1 alloy with a crystalline grain structure is a soft magnetic material since it has good values of permeability while maintaining a saturation magnetization. Thermal annealing of an amorphous melt spun alloy in the temperature range 480-510°C produces a crystalline dispersion of Fe(Si) particles with diameter of the order of 14 nm embedded in a residual amorphous matrix with a higher crystallization temperature. In this work we correlate experimental measurements of grain size and crystallized fraction of an annealed amorphous Fe 73.5 Si 15.5 B 7 Nb 3 Cu alloy, obtained, respectively, by X-ray diffraction and differential scanning calorimetry, with the particle size observed by transmission electron microscopy. The structural development is explained by considering the rejection of insoluble alloy atoms during crystallization with the formation of diffusion layers around the crystals. Growth rates are diminished by the accumulation of the slower diffusing atoms at the growing Fe(Si) interfaces; faster diffusing atoms by alloy enrichment of the residual amorphous matrix can cause a decrease in the nucleation frequency.

Real-time detection of crystal nucleation and growth in amorphous Zr 55 Cu 30 Al 10 Ni 5 was performed for the first time. The experiments were performed at the European Synchrotron Radiation Facilities (ESRF) using monochromatic beam with energy of 90 keV corresponding to a X-ray wavelength of 0.137 A. Full X-ray spectra in transmission were obtained every 3 s. Crystallization was monitored both during heating of the amorphous alloy and during cooling of the liquid alloy to detect differences in the nucleating crystalline phases. We found that crystallization of the amorphous phase occurs via initial nucleation and growth of a metastable phase that transforms to equilibrium tetragonal Zr 2 Cu before melting. However, no trace of nucleation of the metastable phase was obtained during cooling of the liquid alloy from above T m and Zr 2 Cu formed directly from the liquid.

The Fe–6.5 wt.% Si alloy is an excellent soft magnetic material. However, it is too brittle to be hot/cold-rolled since its ordered structure induces the formation of dissociated superlattice dislocations and correlated high stress concentrations leading to premature fracture. The addition of aluminum to high silicon electrical steels, combined with high solidification rates of the spray forming process, can alter the kinetics of these ordering transformations offering the possibility to obtain thin sheets through the hot/cold rolling process. The aim of this work was to determine the magnetic properties of spray-formed Fe–6.5 wt.% Si–1.0 wt.% Al alloy in the “as-sprayed” condition and after hot/cold rolling. After annealing at 973 K for 1 h, the best magnetic properties were observed in the rolled samples. This result is due to the elimination of microstructural defects and porosity and the formation of DO 3 ordered structure.

Based on a lattice model analysis of fracture surface energy of a crystal with diamond structure, this paper presents a theoretical evaluation for toughening the crystal through decreasing the rotation rigidity constant of crystal inter-bonds while increasing or keeping the binding energy. For a silicon crystal the obtained result shows that the improved toughness is 53% higher than the initial toughness if the rotation rigidity constant is decreased to 70% of the initial one while retaining the binding energy. The toughening method is also applicable to a wide range of solid materials by decreasing the shear modulus and maintaining or improving the tensile strength of the material. This new toughening mechanism has explained why the toughness improvement of Al 2 O 3 SiC nanocomposite is less dramatic than the strength one. The paper suggests the rotation toughening as a general consideration in the design of solids with high strength and good toughness, and emphasizes the importance of rotation flexibility for material toughening.

A single crystal of a Nb-1%Zr alloy was internally oxidised at 1000°C for 70 h to produce a fine precipitate of zirconia. Detailed electron microscopy, including moire fringe and lattice image analyses, was used to determine both the crystal structure of the panicles and their orientation relationship to the matrix. Zirconia particles with the cubic structure were identified as the major precipitate and these had the Bain orientation relationship to the matrix i.e.: (001) ppt ∥ (001) Nb and [100] ptt ∥ [110] Nb . Occasionally, the monoclinic form of zirconia was found also.

The demand of automotive industries for parts with high overall quality, low costs and reduced time to market, forced suppliers to search alternative materials and manufacturing processes. Hot forgings with microalloyed steel represent an extensive application in automotive parts. The main objective of this work was to study the microstructures by transmission electron microscopy (TEM) and mechanical properties of 27MnSiVS6 microalloyed steel deformed by ausforming, warm forging and hot forging.Workpieces were heated for 15 minutes at 1150 °C before hot forging and 800 °C before warm forging.Two different ausforming tests were carried out: in the first group workpieces were heated for 15 minutes at 1150 °C, cooled to 800 °C at a cooling rate of 8.7 °C/s and then deformed. In the second group the conditions were kept constant except for the heating temperature of 1000 °C. All forged products were air cooled after deformed. Ausforming products presented the best mechanical properties. TEM analysis showed that strengthening by vanadium carbonitride precipitates was the main hardening mechanism of both ausformed and hot forged products while warm forgings were strengthened by the higher dislocation density. © 2011 Published by Elsevier Ltd. Selection and peer-review under responsibility of ICM11

The effect of zirconia particles on the deformation of niobium single crystals has been studied over the temperature range 4K to 373K. Transmission electron microscopy was used to characterize the dispersion and to observe directly the interaction between dislocations and the precipitate particles. Large numbers of prismatic loops were observed lying in rows along the direction of the primary Burgers vector. At high deformation temperatures the stress-strain curves showed low, linear hardening and as the temperature was reduced this was preceded by a small parabolic stage. At the lowest temperatures of deformation mechanical twinning occurred. The slip plane, determined by multisurface analysis, was usually (101) but at 77K (312) was observed. The particles did not have a dramatic effect on either the stress-strain curves or the parameters defining thermally-activated flow but raised the flow stress at all temperatures and slightly reduced the tendency to twin.