Extraction Replica Technique Research Articles

A cross-section precipitate extraction replica technique for surface-modified alloys

A precipitate extraction technique has been developed that, with simple modifications, should be applicable to a wide range of surface-modified alloys. In the example presented, a 2.25% Cr-1% Mo steel was irradiated with 14-meV nickel ions to produce a 3-μm-thick surface damage zone. The irradiated specimen was subsequently electroplated with iron, sectioned, and metallographically polished, and carbide extraction replicas were prepared by a multistage procedure. Using these techniques, the number density, size, morphology, crystallography, and chemistry of precipitates can be readily studied as a function of depth in the iradiated zone, i.e., versus displacement damage, injected ion effects, preimplanted gases, etc.

On application of the carbon extraction replica technique for the determination of second phase particles dispersed into metal matrix

Experimental data on the characterization of some specific Cu-Cr 2O 3 and Cu-SiO 2 dispersions have been treated in order to test several aspects of the carbon extraction replica technique. Estimates of the volume fraction of the second-phase particles by this means were found in error by varying degrees up to a factor of six. Moreover, no correlations were found between the error factor and significant dispersion parameters such as morphology and size. Therefore, it is concluded that the technique should not be used even for comparative estimates of the volume fraction.

Microanalysis of TiNb carbonitrides in HSLA steels

The microchemistry and morphology of Ti- and Nb-rich carbonitrides formed during continuous casting in some HSLA steels, differing only in their Nb content, have been investigated in order to characterize the effect of Nb on the nucleation and growth process of these particles. Precipitates were extracted using the carbon extraction replica technique and analyzed in a VG-HB 5 STEM by EDS. They exhibit large composition gradients and their morphology is roughly correlated to their size. A model based on the formalism of ternary solubility products in liquid iron and in austenite is developed to explain satisfactorily these composition gradients, and gives the composition of newly formed nuclei in austenite and that of the last deposited layer of precipitates. Nuclei appear as spherical particles, grow by interface instability to polyhedral particles, then to dendrites, with secondary protrusions developed from the primary arms also as a result of an interface instability process.

Electrolytic Extractions of Precipitates From Steel Alloys

During aging of an iron based alloy, the degree of preparation has significant effects on the properties of the alloy. Long-term heat treatments can produce rather large precipitates. In order to obtain compositional and/or structural information from these large precipitates, it is often necessary to examine them in the absence of the surrounding matrix. However it has been found that the extraction replica technique is reliable only for particles 1 μn in size or less. Any larger particle tends to stay embedded in the matrix. We have found electrolytic extraction from the this bulk to be the only reliable way to obtain precipitate particles larger than 1 um. By modifying a gravimetric-vacuum filter assembly, a new method of extraction has been developed, eliminating the time consuming and laborious steps of centrifuging the electrolyte, retrieval of precipitates from test tubes, vacuum drying, and acid cleaning of glassware.

Chemical analysis of the submicron binder phase in hard metals

Chemical Analysis of the Submicron Binder Phase in Hard Metals The chemical analysis of the cobalt binder phase in sintered hard metals poses severe problems if performed by means of physical methods of surface analysis, such as SIMS, EMPA or AES. Compared with their limit of lateral resolution the average mean free path of the binder phase between the carbide particles, especially in micrograin hard metals, is less than 500 nm and thus too small. An electrochemical technique has been developed by which the carbide phase can be selectively etched away from the surface of a polished section, leaving the cobalt binder phase chemically and morphologically unchanged. The carbide-free cobalt binder phase can now be separated from the bulk hard metal using a technique similar to the well-known extraction replica technique commonly applied in transmission electron microscopy. The extracted binder phase can then be analyzed by X-ray fluorescence or other methods.

Precipitation Behavior of Boron in High Strength Steel

The hardenability of boron steel is afected by the precipitation behavior of B. Precipitates in the B containing steel were studied by extraction replica technique at the successive manufacturing steps from hot-rolling to heat treatment.When steels are hot-rolled after heating at 1300°C for 1h, changes of B precipitates with the cooling rate after hot-rolling are as follows:(1) When steels are water-quenched (cooling rate of 90000°C/min) after hot-rolling, no precipitates can be observed on γ grain boundaries.(2) When steels are air-cooled (cooling rate of 300°C/min) after hot rolling, BN precipitates on γ grain boundary region.(3) When steels are furnace-cooled (cooling rate of 0.67°C/min) after hot-rolling, AIN grows radially from BN which has precipitated before the nucleation of AIN. AlN formed on BN during furnace-cooling is dendritic.By reheating at a rate of 15°C/min a specimen which has been waterquenched after hot-rolling (above-mentioned as (1)), the following B precipitates appear depending upon the temperature range:(1) Below 880°C, M23(CB)6 precipitates and coagulates on prior grain boundaries.(2) Above 900°C and below about 1000°C, BN appears on prior grain boundary region which has been previously occupied by M23(C, B)6. M23 (C, B)6 is no longer observed at this stage.(3) Heating at around 1000°C, AlN which is not dendritic but acicular grows radially from BN. The size of BN diminishes with growth of acicular AlN.The formation of AlN on BN is interpreted as a transit from the nonequilibrium to equilibrium state in Al-B-N system in steels.According to Pease, BN (hexagonal close packed) has the same crystal structure as that of graphite. Because BN in steels was revealed to have spherulite morphology such as spherical graphite, it is considered that [00.1] axes of BN are arranged in radial fashion and (00.1) planes are perpendicular to them, by an analogy to the crystal arrangement of spherical graphite. As the growth direction of AlN is [0.01]AlN, it is considered that an orientation relationship of (00.1)BN//(00.1)AlN is satisfied when AlN grows on BN.

An improved extraction replica technique for the microanalysis of inclusions

An improved extraction method for analyzing inclusions in the microprobe or scanning electron microscope (SEM) has been developed using a plastic extraction medium, replacing one of electroplated metal used previously. A plastic substrate simplifies correction procedures in analyzing small particles by minimizing electron and X-ray interferences between the extracted material and the extraction medium. A number of polymers have been tested with respect to their stability under electron bombardment. Both unfilled polyimide and diallyl phthalate resins give a satisfactory performance under most probe and SEM conditions, although the latter requires a preliminary in situ beam fixation treatment. Epoxy-type resins are not stable under irradiation and break down structurally at all electron beam current densities.

Kinetics of MnS precipitate coarsening in 3pct Si-Fe sheet

The growth kinetics of MnS in a 3 pct Si-Fe matrix containing excess manganese were characterized at temperatures of 925°, 975°, and 1025°C by an electron microscopy extraction replica technique. The average radius of coarsened particles at timet, •rt, exhibited Greenwood’s predicted dependence for diffusion-controlled coarsening; namely, r3t= r3 0+kt where r-o is the critical radius for growth andk is the rate constant. Growth rates compared favorably to those calculated from diffusion-controlled coarsening theories assuming that growth was controlled by the diffusion of sulfur. The experimentally determined activation for coarsening, ~67 kcal, was attributed to the sum of the activation for the dissolution of MnS, ~24 kcal, and for the diffusion of sulfur, ~49 kcal.

Analytical-preshadowed extraction replica technique

Submicroscopic particles in precipitation hardening superalloys are studied using extraction replica electron microscopy. Equations developed by McCall and Boyd to evaluate precipitate size, volume fraction, and interparticle spacing from extraction replica electron micrography were recently modified by Abrams to more accurately determine the volume of material from which the precipitate particles are extracted. This paper reviews the application of Abrams' modification to the study of gamma-prime precipitate in superalloys. The analytical approach of Abrams was found to be unsuited to superalloys which contain a large volume fraction precipitate of uniform size.

An analytical method applicable to the preshadowed extraction replica technique

Submicroscopic particles in precipitation hardening superalloys are studied using extraction replica electron microscopy. Equations developed by McCall and Boyd to evaluate precipitate size, volume fraction, and interparticle spacing from extraction replica electron micrography were recently modified by Abrams to more accurately determine the volume of material from which the precipitate particles are extracted. This paper reviews the application of Abrams' modification to the study of gamma-prime precipitate in superalloys. The analytical approach of Abrams was found to be unsuited to superalloys which contain a large volume fraction precipitate of uniform size.

A new extraction replica technique for inclusion analysis in the microprobe

A new extraction replica technique for inclusion analysis in the microprobe

A selective extraction replica technique for carbides in steels

An improved technique is described for obtaining high resolution extraction replicas from steels. Carbon replicas are dry-stripped from etched steel using a collodion backing. The replicas obtained are not only cleaner because they are free from surplus etching debris, but allow selective extraction of very fine precipitates in the presence of massive carbide particles.

Etch-Shadow Extraction Replica in Fracture Studies

A new replica technique for electron microscopy of fracture surfaces is described, which can reveal the relationship between the microstructural features of metals and alloys and the detailed topography of their fracture surfaces. This etch-shadow extraction replica technique combines in one replica the salient features of shadowed-surface replicas and precipitate-extraction replicas. Thus a bridge is provided between the fracture topography, which is governed mainly by the effects of fracture-velocity changes, and the significant microstructural features such as precipitates, grain boundaries, etc.

Extraction ReplicaによるCu-Cr-Ti合金の析出物に関する研究

Extraction ReplicaによるCu-Cr-Ti合金の析出物に関する研究

X-ray diffraction studies on precipitates and inclusions in steels using an extraction replica technique

A simple extraction method is described in which precipitates and inclusions in steels can be isolated for identification by X-ray diffraction. The included material is removed from the metal surface embedded in a thin plastic replica, which is then formed into a small, compact, cylindrical specimen suitable for powder cameras. The scope of the method is discussed, and examples of the application of the method are given. Because the extraction period is only a few minutes, the method has several advantages over bulk extraction methods. In addition to the more stable constituents, iron carbide, iron nitrides and metal sulphides have been successfully extracted.

Observation of Precipitates and Inclusions in Steel by Extraction Replica Technique

Observation of Precipitates and Inclusions in Steel by Extraction Replica Technique

Evaporated Carbon Film for Use in Extraction Replica Technique

The author has studied on extraction replica technique using evaporated carbon film as replica material. The evaporated carbon film has many advantageous characteristics needed to act as extraction replica such as being amorphous, chemically inert and stable for electron bombardment or having large machanical strength, etc. It is confirmed that this new extraction replica technique is simple and effective method having the advantage of locating precipitation since carbon is excellent as shadowing material.