Alpha Beta Region Research Articles

Characterization of hot deformation behavior of TC32 titanium alloy

The hot deformation behavior of TC32 alloy is investigated in the temperature range of 873~948°C and strain rate range of 0.01, 0.1, 1, and 10s−1 by hot compression experiments, and the constitutive relationship of TC32 alloy is established on the base of the Arrhenius equations. It is found that, with an increase in deformation temperature and the strain rate reduction, the flow stress decreases, and the deformation mechanisms of TC32 alloy exhibit dynamic recovery feature within the high-temperature region and recrystallization feature within the low-temperature one. Deformation activation energy values are 404.7 kJ/mol in the alpha-beta region and 526.6 kJ/mol in the beta region. Finally, the constitutive equation of TC32 titanium was established.

Hot ductility behavior of near-alpha titanium alloy IMI834

Abstract The hot ductility of rolled IMI834 titanium alloy has been studied by conducting tensile tests with a strain rate of 0.1 s−1 and temperature range of 750–1 100 °C to obtain the optimum hot working conditions. The alloy showed minimum hot ductility in the lower alpha–beta region in the temperature range 750–950 °C. Further microstructural characterizations showed improvement in hot ductility by increasing temperature, which was attributed to reduction of volume fraction of high strength alpha phase. The best hot ductility was observed at 1 000 °C, i. e. in the upper alpha–beta region. The better hot ductility at higher temperature could be related to the increase in the volume fraction of beta phase and the occurrence of dynamic restoration phenomena. The second decline in hot ductility appeared at higher temperatures in the beta region and was attributed to the high stacking fault energy and self-diffusion of beta phase leading to limitation of dynamic recrystallization.

Influence of thermomechanical processing on microstructural evolution in near-α alloy IMI834

The effect of processing parameters on the evolution of the microstructural characteristics of IMI834 were examined over the temperature range 950–1125 °C at constant strain rates of 0.001–1 s −1 and true strains up to 1.2. During isothermal deformation, differences in the flow softening behavior were observed for processing in the single-phase beta region, as compared to the two-phase alpha–beta region, which has been related to differences in the structural changes occurring in IMI834. In particular, deformation processing of the alpha–beta structure was observed to work the lamellar alpha structure of the transformed beta grains without recrystallization of either phase, whilst microstructural development in a predominately beta structure resulted in the formation of dynamically recrystallized grains that were necklaced around the deformed and elongated beta phase. For the later case, the variation in the dynamically recrystallized grain size was determined to follow a Zener–Hollomon relationship between a strain rate range 0.001 and 1 s −1.

ALLVAC Ti-17

Abstract Allvac Ti-17 is a high-strength deep-hardening alloy. The alloy is alpha-beta, but beta-rich, and can be worked in both the beta and alpha-beta region. The alloy is commonly referred to as grade 17 in specifications. This datasheet provides information on composition, physical properties, hardness, and tensile properties. It also includes information on high temperature performance and corrosion resistance as well as joining. Filing Code: TI-135. Producer or source: Allvac, An Allegheny Technologies Company.

European collaborative study of luteinizing hormone assay: 1. Epitope specificity of luteinizing hormone monoclonal antibodies and surface mapping of pituitary and urinary luteinizing hormone

This report describes the results of the first part of the collaborative study organized by a working group sponsored by the Community Bureau of Reference of the European Community Commission. The whole study was designed to understand the causes of discrepancy among LH immunoassay methods. In the parent work, we studied the characteristics of 55 monoclonal antibodies to LH which allowed us to establish a detailed map of the antigenic surface of the hormone. In the present report we used this information to interpret the discrepancy in LH concentrations assayed with 12 different methods in 300 sera from subjects with various clinical conditions. The 55 monoclonal antibodies provided by 11 commercial companies were tested in various experiments: the apparent affinity of the antibodies was, generally but not always, higher for LH presented by a second antibody coated to plastic than for LH directly coated to plastic; 26% of the antibodies recognized the alpha subunit, 26% the beta subunit and 48% reacted only with the holomolecule (anti-alpha beta); only 28% of the antibodies were strictly specific for LH. Criss-cross experiments allowed us to distinguish 13 antigenic regions on the surface of LH: 6 were located on the alpha subunit, 3 on the beta subunit and 4 on the holomolecule. The monoclonal antibodies to the alpha beta regions further separated into 12 clusters of reactivity. Accordingly, LH appeared to exhibit at least 21 epitopes. Comparison of the immunoreactivity of various LH preparations indicated that highly purified pituitary LH and immunoaffinity purified urinary LH reacted similarly with the monoclonal antibodies and strongly differed from crude urinary LH. These data indicated that the immunoreactivity of an LH preparation depends mainly upon the degree of purification and not that much upon the origin of the preparation. The epitope specificity of the monoclonal antibodies used in 11 commercially available LH assay kits was also determined: 10 kits used at least one anti-alpha beta monoclonal antibody associated with an anti-beta monoclonal antibody in 7 cases or another anti-alpha beta monoclonal antibody in 3 cases; one kit used an anti-alpha monoclonal antibody associated with an anti-beta monoclonal antibody. None of the kits were strictly identical with regards to the epitope specificity of the monoclonal antibodies used.

Calorimetric investigation of the domain structure of human complement C1.lovin.s: reversible unfolding of the short consensus repeat units

Cl-s is a multidomain serine protease that participates in Ca2+-dependent protein-protein interactions with other subcomponents of Cl, the first component of human complement. Proteolytically derived fragments that retain some of the functional properties of the parent protein have been isolated, and their thermal stability has been investigated by differential scanning calorimetry. Three endothermic transitions are observed in whole Cl-s near 37, 49, and 60 degrees C in 0.05 M Tris-HCl, pH 7.2, containing 0.22 M NaCl and 0.1 mM EDTA. The first (37 degrees C) and third (60 degrees C) transitions are also seen in Cl-s-A, a derivative comprised mainly of the intact nonenzymatic A chain. The second (49 degrees C) and third transitions are seen in Cl-s-gamma B, a fragment comprised of the intact B chain, disulfide linked to the C-terminal gamma region of the A chain. Thus, the first transition, which is alone stabilized by Ca2+, corresponds to the melting of the N-terminal alpha beta region of the A chain, the second to the melting of the catalytic B chain domain, and the third to the gamma region. The gamma region is comprised of two homologous short consensus repeat (SCR) motifs that are also found in several other complement and coagulation proteins. A new 24-kDa fragment, Cl-s-gamma, which contains these two SCRs, was isolated from plasmic and chymotryptic digests of Cl-s-A. Cl-s-gamma exhibits a reversible transition near 60 degrees C corresponding to the highest temperature peak in whole Cl-s and Cl-s-A.(ABSTRACT TRUNCATED AT 250 WORDS)

Isolation and functional characterization of the proenzyme form of the catalytic domains of human C1r

The proenzyme form of C1r catalytic domains was generated by limited proteolysis of native C1r with thermolysin in the presence of 4-nitrophenyl-4'-guanidinobenzoate. The final preparation, isolated by high-pressure gel permeation in the presence of 2 M-NaCl, was 70-75% proenzyme and consisted of a dimeric association of two gamma B domains, each resulting from cleavage of peptide bonds at positions 285 and 286 of C1r. Like native C1r, the isolated domains autoactivated upon incubation at 37 degrees C. Activation was inhibited by 4-nitrophenyl-4'-guanidinobenzoate but was nearly insensitive to di-isopropyl phosphorofluoridate; likewise, compared to pH 7.4, the rate of activation was decreased at pH 5.0, but was not modified at pH 10.0. In contrast, activation of the (gamma B)2 domains was totally insensitive to Ca2+. Activation of the catalytic domains, which was correlated with an irreversible increase of intrinsic fluorescence, comparable with that previously observed with native C1r [Villiers, Arlaud & Colomb (1983) Biochem. J. 215, 369-375], was reversibly inhibited at high ionic strength (2 M-NaCl), presumably through stabilization of a non-activatable conformational state. Detailed comparison of the properties of native C1r and its catalytic domains indicates that the latter contain all the structural elements that are necessary for intramolecular activation, but probably lack a regulatory mechanism associated with the N-terminal alpha beta region of C1r.

Aldehyde dehydrogenase from human liver. Primary structure of the cytoplasmic isoenzyme.

Analysis of CNBr fragments and other peptides from human liver cytoplasmic aldehyde dehydrogenase enabled determination of the complete primary structure of this protein. The monomer has an acylated amino terminus and is composed of 500 amino acid residues, including 11 cysteine residues. No evidence of any microheterogeneity was obtained, supporting the concept that the enzyme is a homotetramer . The disulfiram-sensitive thiol in the protein, earlier identified through its reaction with iodoacetamide, is contributed by a cysteine residue at position 302, while the cysteine which in horse liver mitochondrial aldehyde dehydrogenase is reactive with coenzyme analogs appears to correspond to either Cys-455 or Cys-463. Analysis of glycine distribution and prediction of secondary structures to localize beta alpha beta regions typical for coenzyme-binding are not fully unambiguous, but suggest a short region around position 245 as a likely segment for this function. In this region, sequence similarities to parts of a bacterial aspartate-beta-semialdehyde dehydrogenase and a mammalian alcohol dehydrogenase were noted. Otherwise, no extensive similarities were detected in comparisons with characterized mammalian enzymes of similar activity or subunit size as aldehyde dehydrogenase (glyceraldehyde-3-phosphate dehydrogenase and glutamate dehydrogenase, respectively).