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Ductile iron bars (DIBs) with a diameter of 145 mm, used for plunger pump production, were made by the horizontal continuous casting (HCC). The microstructure of the samples cut at three locations with different distances away from the surface (~20 mm from the surface, half of the radius and the center of the HCCDIBs) were investigated. The mechanical properties were measured by tensile and torsion tests. Results show that after the spheroidization of graphite, the iron matrix incorporates the nodules of Format I, Size 8 close to the surface, Format I, Size 7 at the half of the radius from the surface, and Format II, Size 6 in the centre of the bar, according to the ASTM A247 standard. The content of pearlite in the matrix changes from 55% (~20 mm from the surface) to 70% (half of the radius) and 80% (the center of the HCCDIBs). The strengths in tension are 552, 607 and 486 MPa with the elongations of 12.5%, 10.5% and 5.8% in samples cut at these three locations from the surface to the centre, respectively. The strength in torsion is equal to 558, 551 and 471 MPa at corresponding torsion angles of 418°, 384° and 144° respectively to the same distance from the bar surface. Fracture in tension is manifested via crack propagation through the interface between graphite nodules and matrix (Mode I), while in torsion the fracture is caused by the shear of graphite nodules (Mode II). It is shown that the transition between two fracture modes is also dependent on the size of graphite nodule. Typically, fracture Mode I was observed for nodules of smaller diameter (less than 22.7 μm) and fracture Mode II was seen for nodules of greater diameter (more than 24.8 μm).

A strong and ductile Mg–6.0%Zn–1.0%Y–0.6%Ce–0.6%Zr alloy was developed. The alloy was first cast into billets which were rapidly solidified into ribbons, comminuted and extruded. Some of the extrusions were subjected to reciprocal extrusion processing. The microstructures of the alloy prepared by the different processes were analyzed by optical microscopy (OM) as well as high resolution scanning electron microscopy (HRSEM) and transmission electron microscopy (TEM). The microstructure of the cast consisted of coarse grains with average grain size of about 45 μm with intermetallic networks at grain boundaries. The microstructure of the extrusions made of rapidly solidified chips was not uniform; it was fine at the circumference, but coarser in the central area. A low density of defects in the form of unwelded rapidly solidified (RS) ribbon particles in the center of the extrusion was also present. The microstructure of the alloy subjected to reciprocating extrusion was more uniform with average grain size of 1.3 μm and homogeneously dispersed strengthening particles 80 nm in diameter.

Based on the commercial alloy ZK60 which contains 6%Zn, high strength Mg-6.0%Zn-1.0%Y-0.6%Ce-0.6%Zr magnesium alloy bars of 10 to 50 mm in diameters were prepared by rapid solidification (RS) and extrusion processes （RSE）. For those RSE solid bars, the ultimate tensile strengths steadily maintain on a level of 490 to 520 MPa, the elongations are between 6 to 10%. The HV50 hardness is between 85 and 90. In order to reveal materials microstructures both RS ribbons and RSE solid bars, the Mg-6.0%Zn-1.0%Y-0.6%Ce-0.6%Zr alloy was analyzed with an optical microscopy (OM), a scanning electron microscopy (SEM) equipped with an energy-dispersive X-ray spectrometer (EDS) and an X-ray diffraction apparatus. It was found that the microstructure of the RS ribbon consists of super saturated (Mg) solid solution; thermally stable Mg3Y2Zn3 (W) and Mg7Ce2 intermetallic compound particles which uniformly dispersed interior grains and W and Mg7Ce2 compound networks at grain boundaries. After extrusion, the microstructure of RSE Mg-6.0%Zn-1.0%Y-0.6%Ce-0.6%Zr solid bar consists of the same phases as the RS ribbons. The networks existing at RS ribbon’s grain boundaries were break up into submicron particles and dispersed uniformly on the matrix formed after extrusion.

Electrodeposited Cu/Ni multilayers with different modulation lengths Λ = 4–18 nm were examined by means of x-ray diffraction and transmission electron microscopy. Preferred orientations of [111], [110], and [001]-types, as determined from relative x-ray diffraction peak intensities, were seen in the multilayers. By means of computer simulations of the measured x-ray diffraction spectra, several parameters of the multilayers, such as Λ-values and fluctuations ΔΛ, as well as lattice strain, were determined. Multilayers having large Λ were found to be fully relaxed due to interfacial dislocation formation. In short Λ [001]-texture multilayers partial strain relaxation occurs, probably due to the incorporation of Cu into the Ni layers. Both of the processes lead to the diffuse Cu/Ni interfaces. Short wavelength multilayers with a [111]-preferred orientation were almost fully strained. The importance of the [111]-texture in the improvement of mechanical strength of Cu/Ni multilayers resulting from its enhanced ability for stain accommodation is discussed.

The Ti layers in Al/Ti multilayers are shown to transform from hexagonal close packed in the as-deposited multilayers to face centered cubic on ion milling in cross-section. By examining the change in free energy of the system on transformation it is demonstrated that interfacial, surface and strain free energies cannot overcome the theoretically predicted 0.08 eV/atom difference in bulk free energy between f.c.c. and h.c.p. Ti. Based on experimental observations of f.c.c. Ti in multilayers, it is argued that this value is too large.

Rapidly solidified alloys of Au-2wt%Ti, Au-3 wt% Ti and Au-5wt% Ti have been examined using transmission electron microscopy in order to investigate both the nature of structural order induced by rapid solidification and the evolution of long-range order during post-solidification heat-treatment. 〈1½0〉 special-point order is identified as a feature of the as-solidified microstructures and an intermediate state of order, incorporating both elements of the long-range-ordered (D1a) structure and elements of 〈1½0〉 special-point order, is observed to be stable up to the nucleation temperature of the equilibrium (D1a) Au4Ti phase in Au-3 wt% Ti. The evidence from electron diffraction patterns is discussed and interpreted by considering the nature and distribution of the three-dimensional diffuse streaking observed in zone-axis patterns from a variety of different orientations. The compositions examined demonstrate that these materials are members of the ‘special-point’ family of alloys and that incorpo...

Precipitation at 450 °C was studied in melt-spun ribbons containing up to 15 wt pct Mn in solid solution in Al. The as-spun ribbons were microsegregation-free at compositions up to 5 wt pct Mn, but in more concentrated alloys a cellular microstructure was present. Upon annealing, four precipitate phases are observed, some of them being found preferentially on cell boundaries and others being found within the cells. Al6Mn, G, and the Gℍ phase can coexist for long times at 450 °C, but the G phase appears to be slightly more stable. A less stable T phase was detected in Al-5 wt pct Mn foils following short annealing periods. The supersaturation of the Al matrix can persist for many hours in alloys containing up to 3 wt pct Mn, but is essentially gone after 1 hour in alloys with 5 wt pct Mn or more.

A Ti-32wt% Fe alloy was rapidly solidified by the melt-spinning technique. Three microstructures are found in the melt-spun ribbon of the alloy: the first contains small FeTi particles in aΒ matrix, the second is a cellular microstructure composed ofΒ and FeTi and the third is a eutectic of these phases. The correlation between various solidification and cooling rates across the ribbon width to the three microstructures is explained.

An advanced method for investigation of multicomponent systems is proposed. Thin wedged-shape films of pure components are subsequently deposited to form a multilayered structure with continuously-varying composition as a function of sample location, providing a large number of differently composed samples in one deposition run. Each sample is then subjected to various heat treatments, and phase content as well as the microstructure formed is under investigation.In this study an Au-Ag-Cu multilayered structure was sputtered at a room temperature onto 55 Formvar-coated Mo grids. The satellite-like X-Ray Diffraction (XRD) patterns of these samples revealed the formation of an artificial composition-modulated ternary superlattice, complete destruction of which was observed during heat treatments, where phase formation according to the ternary Au-Ag-Cu phase diagram took place.Several aspects of phase formation were analyzed using XRD, Electron Probe for Micro- Analysis (EPMA) in Scanning Electron Microscopy (SEM), and Scanning Transmission Electron Microscopy (STEM) combined with Selected Area Electron Diffraction (SAED), Digital X-Ray Mapping (DXM), Secondary Electron Mapping and EPMA methods.

1 μm ZnO films were deposited on SiO2 by reactive sputtering using a D. C. magnetron gun. The microstructure, orientation and chemistry of the deposited layers were examined. It is shown that the oxygen partial pressure plays an important role in the structure of the layer through a mechanism of surface diffusion.

High resolution electron microscopy of plasma-assisted chemical vapor deposition (CVD) diamond films was performed. The film was fine-grained with a grain size of 0.1 micrometers . Several features of the microstructure were studied and their importance to the understanding of the diamond film growth was evaluated. The observations include: (1) Twinning density rises as a function of the distance from the center of the crystal. (2) The twins have an important role in the rapid growth of this kind of film The re-entrant angle between intersecting twins serves as a nucleation site for the growth of new (111) planes. (3) The center point of a twin quintuplet has five re-entrant angles and thus serves as a preferred nucleation site for new planes as the crystal grows. (4) Misfit boundaries, being the locus of intersection points of the growing planes on two adjacent twins, can serve as an indicator for the local crystal growth direction. The central nucleation site for the growing planes can thus, in many cases, be traced back to a quintuplet twin point.

Electron beam solidification passes have been performed on a series of Ag-Cu alloys between 1 wt pct Cu and the eutectic composition (28.1 wt pct Cu) at speeds between 1.5 and 400 cm per second. At low growth rates conventional dendritic or eutectic structures are obtained. The maximum growth rate of eutectic structure is 2.5 cm per second. At high growth rates microsegregation-free single phase structures are obtained for all compositions. The velocity required to produce this structure increases with composition for dilute alloys and agrees with the theory of absolute stability of a planar liquid-solid interface with equilibrium partitioning. For alloys between 15 and 28 wt pct Cu, the velocity required to produce the microsegregation-free extended solid solution decreases with composition and is related to nonequilibrium trapping of solute at the liquid solid interface. At intermediate growth rates for alloys with 9 wt pct Cu or greater, a structure consisting of alternating bands of cellular and cell-free material is obtained. The bands form approximately parallel to the local interface.

The UNS C17510 commercial Cu-Ni-Be alloy was heat treated in three different ways: AT, simple aging; HT, aging in the hardened condition; and TMT, a special thermo-mechanical treatment. It was found that in the electrical conductivity range of 50 to 60 pct IACS the TMT treatment results in a much higher yield strength than either the AT or the HT treatments. Three types of particles have been identified: relatively large primary beryllides, very small -γ precipitates, and small non-coherent nickel-rich beryllides (NRB). Based on measurements of the size distribution of NRB pre-cipitates and by means of an existing theoretical model, it was shown that these precipitates together with a dense dislocation network are responsible for the increased strength of the alloy follow-ing TMT.

The microstructure of rapidly solidified Al−Mn alloys containing 18 to 25.3 wt pct Mn was studied by transmission electron microscopy. One of the phases found in the microstructure exhibits icosahedral symmetry manifested in electron diffraction patterns having five-fold symmetry. A new structural concept is proposed to account for the observed electron diffraction patterns. The structure is assumed to be composed of many connected polyhedra. Although not forming a regular lattice, such structures are able to produce sharp diffraction peaks. The terminal stability and transformation of the icosahedral phase was also studied and reported.

Melt-spun ribbons of aluminium containing up to 15 wt% chromium were examined in the as-spun condition and after annealing. The more concentrated alloys contained multi-phase spherulites embedded in an α-Al matrix: chemical microanalysis showed the average composition of the spherulite core to be 22 ± 2 wt% chromium. The kinetics of precipitation at grain boundaries and within the matrix were determined by TEM and X-ray diffraction. Three very similar Al-Cr intermetallic phases are present under equilibrium conditions, but most of the precipitates in the melt-spun ribbons could be identified as Al7Cr.

A Ni-W eutectic alloy was subjected to a process of unidirectional solidification (UDS) by the Bridgman-Stockbarger technique. Three phases were identified by transmission electron microscopy, namely: W fibers, a solid solution matrix of W in Ni, and Ni4W precipitates of the Dla structure in the matrix. The growth axis of the W-fibers was found to be and the orientation relationship between them and the Ni(N) matrix was identified as the Bain type, so that (100)bcc ‖ (100)fcc. The shape of the Ni4W precipitates varies from equiaxial at high solidification rates to elongated plates at low rates. The orientation relationship between the precipitates and the matrix is the same for all solidification rates. The microstructure of specimens subjected to creep deformation was studied and the deformation modes were identified. These include dislocations and microtwins that originate mainly at the boundary between the Ni(W) matrix and the W-fibers. In some specimens the creep test was carried out after solution treatment at 1030 °C followed by quenching, which resulted in a Ni(W) matrix reinforced with W-fibers without Ni4W precipitates. The microstructural changes during this creep process and the fracture surface were studied by SEM and TEM.

Ti-Fe binary alloys were rapidly solidified by the melt-spinning technique, and four compositions were examined: Ti-5 wt pct Fe, which is the critical composition for theβ to ω athermal transformation; Ti-10 wt pct Fe, which represents a hypoeutectoid composition; the eutectoid composition Ti-15 wt pct Fe; and Ti-20 wt pct Fe, as an example of a hypereutectoid alloy. The Ti-5 wt pct Fe rapidly solidified ribbons are composed of two different structures. The first consists of α′-martensite plates inβ matrix and the second, athermal ω particles inβ matrix. The Ti-10, 15, and 20 wt pct Fe alloys are also composed of two structures. These areβ grains and isothermal-like ω particles inβ matrix. A solidification model is suggested which explains the existence of two different microstructures at the same composition and the for-mation of two kinds of ω particles.

The tensile properties of the intermetallic compound TiAl have been determined at several temperatures in the range 25 to 1000°C. Additional variables studied were the influence of strain rate and the effect of exposure to oxidizing conditions prior to testing. The modes of deformation under the various testing conditions were studied in the electron microscope, the modes of fracture were studied in the scanning electron microscope, and these data were correlated with the mechanical properties. The results indicate that the ductilebrittle transition behavior of TiAl at about 700°C is controlled by the trailinga/6 [112] partial dislocation components of thea [011] superdislocations overcoming their pinning barriers. It was also shown that prior exposure to oxidizing conditions does not markedly influence the mechanical properties of TiAl.

The discovery by Shechtman, of five-fold symmetry in rapidly solidified aluminum alloys stimulated world wide interest and activity in the preparation and properties of the materials. Likewise, research on the microstructure of a variety of rapidly solidified aluminum alloys including those containing iron and chromium has been advanced. This report covers the work of two Principal Investigators, Dr. Leo Bendersky and Dr. Dan Shechtman, plus their research collaborators, which has been reported in the scientific literature during the first half of 1986. The five publications reproduced here represent a significant contribution to our understanding of the icosahedral phase and the microstructure of rapidly solidified alloy.

Four aluminum alloys, designed for use at elevated temperatures, supersaturated with iron, chromium and other elements: Ti, V, Zr, were studied. The starting materials were alloy powders made by the RSR (Rapid Solidification Rate) centrifugal atomization process (approx. one million (deg C/sec)) developed by Pratt and Whitney Aircraft and extrusion bars were made from four powders. The as extruded microstructure and the microstructure of the annealed alloys at 482 C (900 F) were investigated by optical and transmission electron microscopy, and by X-ray diffraction. The microstructure included equiaxed grains of aluminum matrix and two types of precipitates, namely: Theta-Al3(Fe,Cr), and Al6(Fe,CR)--which is a metastable phase. The precipitates were different in their shape, size, distribution and location within the grains. The thermal stability of the four alloys was investigated by hardness measurements, following annealing at various temperatures. The alloy structures were found to be stable up to 400 C (750 F). Tensile properties of the alloys were investigated at room temperature, 232 C (450 F) and 332 C (630 F).

During the reporting period, advances were made in three main areas of study, dealing with the following: the Al-Fe system; Pd(77)Si(17)Cu(6); the Phrasor powders. All three studies are designed to further our understanding of different phenomena that occur in the rapid solidification of useful metallic systems. We now have a better understanding of the structure and the solidification sequence of rapidly solidified Al-Fe alloys containing up to 34 wt % Fe. In rapidly solidified ribbons of Pd(77)Si1(7)Cu(6) we were able to detect the first stages of crystallization following heat treatments, and then to observe the advancement of the crystallizing front. We had the first look at two of the Phrasor powders, with a particle size which starts at about 3nm, and detected some phenomena which are inherent to the technique. The only technical problem encountered during the reporting period was related to foil preparation for the Scanning Transmission Electron Microscope (STEM), involving a few alloys, based mainly on silver. These difficulties are expected to be resolved with the purchase of a new ion miller and then these systems will be reinvestigated.

The UNS C17510 commercial Cu-Ni-Be alloy was heat treated in three different ways. It was found that in the electrical conductivity range of 50-60%. IACS the thermo-mechanical treatment results in high yield strength. Three types of particles have been identified: relatively large primary beryllides, very small γ ” precipitates and small noncoherent nickel-rich beryllides.

Rapidly solidified Al containing up to to 15 wt.% Mn was prepared by melt spinning. The alloys were examined by TEM and X-ray diffraction in the as-spun condition and after annealing at 450°C. Four precipitate phases were detected, and their growth kinetics were correlated to subgrain structures in the Al matrix.