Bonding and Fracture Characteristics at α_2/γ Interface in TiAl Alloy with B Addition

The bonding characteristics of (0001)α2||(111)γ interface in two-phase TiAl alloy have beeninvestigated with the recursion method. The results of bond order integral and interaction energybetween atoms are presented. The effects of B on atoms bonding both in constituent phase andat the α2/γ interface have been studied. The correlation between the mechanical propertiesof the alloy and the bonding at the interface has been discussed. The results suggest that Bsegregation to the interface benefits the ductility. This is supported by the related experiment.

Effects of B and Ti on the Toughness of HSLA Steel Weld Metals

Effects of microalloying Ti and B on the microstructures and low temperature toughness of manual metal arc (MMA) deposits were investi- gated.Weld metals containing 200-300 ppm Ti and 29-60 ppm B deposited by manual coated elec- trodes provided an optimum low temperature toughness.The addition of B in weld metals low- ered the γ→α transformation temperature which promoted the acicular ferrite (AF) transformation. Solid solutioned B suppressed grain boundary ferrite as well as side plate ferrite formation and benefited the acicular ferrite formation.Titanium protected B from oxidizing as well as nitriding and formed Ti-Mn silicate inclusions.Ultra-high volt- age electron microscope analyses showed that TiO structure in the Ti-Mn silicate inclusions was the favorable nucleation site for acicular ferrite forma- tion.

INVESTIGATION OF BEHAVIOUR OF B IN Ni_3Al ALLOYS BY POSITRON ANNIHILATION TECHNIQUE

The behuviour of B atoms added to mono-and poly-crystalline Ni_3AI alloys has been investi- gated hy positron annihilation technique(PA T).If the additive of B was less than 1.37 at-%, some of B atoms solid-solutioned interstitially into matrix and distorted the lattice,thus the lifetime (τ) of positron (e^+) Or matrix dilated:the others of them segregated on vacancy-like defects and formed "filling effect",thus the mean lifetime (τ)and S parameters decreased.If B added was increased up to 2.22 at-%,more defects having larger free volume were induced by horide eutectic occurred along grain boundaries and grain interior,thus the τ in vacancy-like defects.τ and S parameters increased remarkably.

ANALYSIS ON EPITOPES OF IGM WITH MONOCLONAL ANTI-ISOTYPIC AND ANTI-IDIOTYPIC ANTIBODIES AGAINST IgM FROM B-CLL

A double antibodies additivity ELISA test was employed to identify the epltopes which can be recognized by monoclonal antibodies (McAbs) against IgM from B chronic lymphocyte leukemia (B-CLL). The computer grouping programme analysis showed that 4 and- isotypic MaAbs could be divided into two groups and 10 anti- idiotype McAbs could be divided into four groups. The result was consistent with that of the indirect sandwich ELISA and inhibition ELISA test. It suggested that there were at least 6 distinct IgM epitopes which can react specifically with 14 McAbs. Our study indicated that the combination of the additivity ELISA test and the computer grouping programme analysis is of help in studying the relationship of the structure and function of antigen.

Correlation of the Mechanical Properties of Polycrystalline Ni_3Al Alloys with Their Electronic Structure

The electronic structure of Ni_3Al alloys with different B contents has been investigated by measuring the positron lifetime spectra.The segregation of B atoms to defects could form strong covalent bondings with Ni and Al atoms and make the electronic structure in those locations similar to that in bulk,thus strengthen their cohesion.The interaction of B atoms,which were solid-solutioned in the crystal lattice of Ni_3Al in a manner of occupying interstitial sites,with Ni and Al atoms resulted in the increase of the density of valent electrons,thus increased the bonding cohesion in bulk.The im- provement of the mechanical properties of Ni_3Al alloys by B doping was due to both“grain bounda- ry effect”and“bulk effect”of B,which correlated with their electronic structure.

Effects of B addition on glass forming ability and thermal behavior of FePC-based bulk metallic glasses

The FePC-based bulk metallic glasses（BMGs）have been demonstrated to possess high plasticity and good soft magnetic properties.However,the relatively poor glass forming ability（GFA）and thermal stabilities limited their application in industries.The effects of microalloying with B in FePC-based BMGs on the GFA and thermal behaviors were systematically investigated.It was found that a small amount of B addition can dramatically enhance the GFA of FePC-based BMGs,which in turn leads to the critical maximum diameter up to 2 mm for full glass formation even using low cost raw materials.The underlying mechanism of the enhancement of GFA from the competing crystalline phase with amorphous phase,the average thermal expansion coefficient and dynamic viscosity were discussed in detail.

Effect of Brazing Conditions on Microstructure and Mechanical Properties of Al_2O_3/Ti—6Al—4V Alloy Joints Reinforced by TiB Whiskers

Al2O3 and Ti-6Al-4V alloy were brazed with Ag-Cu-Ti ＋B fillers in different brazing conditions. Effects of brazing temperature, holding time and additive Ti content on joints microstructure and shear strength were investigated by scanning electron microscopy, energy dispersive spectrometry, X-ray diffraction, transmission electron microscopy and shear testing. Results indicate that TiCu and Ti（Cu,Al） decrease, but Ti2Cu and -Ti2（Cu,Al） increase in brazing seam with increasing brazing temperature, holding time and additive Ti content. Area consisting of Ti3（Cu,Al）30 and TiO near Al2O3 becomes gradually discontinuous from continuity when brazing temperature rises or holding time extends. As Ti additive content increases, TiO is absent near Al2O3, area consisting of only Ti3（Cu,Al）30 thickens. TiB whiskers are in situ synthesized by Ti and B atoms during brazing process. The brazing temperature, holding time and additive Ti content on joints microstructure influence the joints shear strength directly. The shear strength of joints, obtained at 850 ℃ holding for 10 min, reaches the maximum of 78 MPa. According to the experimental results, phase diagram and thermodynamics calculation, the interface evolution mechanism of the Al2O3/Ti-6Al-4V alloy joint was analyzed.

Sintering Behavior and Microwave Dielectric Properties of MgTiO_3 Ceramics Doped with B_2O_3 by Sol-Gel Method

The B2O3-doped MgTiO3 powders and ceramics have been prepared by sol-gel method using Mg（NO3）2-6H2O, Ti（C4H9O）4 and H3BO3 as the starting materials. The sintering behavior and microwave dielectric properties of ceramics prepared from powders with different particle sizes were investigated. The gels were calcined at 650, 700, 750, 800, 850 and 900 ℃ and the derived particle sizes of powders were 20-30 nm, 30-40 nm, 40-60 nm, 60-90 nm, 90-120 nm and 120-150 nm, respectively. The nanoparticles with the size of 30-60 nm benefited the sintering process with high surface energy whereas nanoparticles with the size of 20-30 nm damaged the microwave dielectric properties due to the pores in the ceramics. The addition of B203 used as a liquid sintering aid reduced the sintering temperature of MgTiO3 ceramic, which was supposed to enter the MgTi03 lattice and resulted in the formation of （MgTi）2（BO3）O phase. The B203-doped MgTiO3 ceramic sintered at 1100℃ and prepared from the nanoparticles of 40-60 nm had compact structure and exhibited good microwave dielectric properties： εr=17.63, Q x f=33,768 GHz and Tf=-48X 10-6 ℃-1.

Effect of B_2O_3 Additives on the Sintering and Dielectric Behaviors of CaMgSi_2O_6 Ceramics

The effects of B2O3 addition, as a sintering agent, on the sintering behavior, microstructure and dielectric properties of CaMgSi2O6 ceramic have been investigated. The CaO-MgO-B2O3-SiO2 glassy phase came forth by adding B2O3 into CaO-MgO-SiO2 ceramic powders, and it was advantageous to lower the synthesis temperature of CaMgSi2O6 crystalline phase. Moreover, the emergence of CaO-MgO-B2O3-SiO2 glass phase could effectively lower the sintering temperature of CaMgSi2O6 ceramic and promote the CaMgSi2O6 grains growing. With 6 wt pct B2O3 addition, the densification temperature of CaMgSi2O6 ceramic could be effectively reduced from 1300 to 1100℃, and the dielectric constant （εr） and dielectric loss （tanδ） were： εr=7.61 and tanδ=7.4×10^-4 （1 MHz）.

Removal and occurrence state transformation of Ti impurity in Gd metal

The interaction mechanism of B and Ti in liquid Gd metal was theoretically analyzed,and the occurrence state transformation and removal of Ti impurity were experimentally analyzed in this study.The research results indicated that the B additive reacted with the Ti impurity in liquid Gd metal to form the high-melting-point TiB_(2)at 1673 K.Owing to the low density of TiB_(2)that is far lower than that of Gd,TiB_(2)floated up to the liquid surface,and then,the Ti impurity could be effectively removed from Gd metal.Prolonging melting time and increasing B additive amount could increase Ti removal rate,but the increase in the rate slows beyond a certain duration and B content.The recommended operating parameter,melting time of 60 min and B additive content of 0.1394 wt%could reduce Ti content from 0.1534 wt%to 0.0433 wt%,and the removal rate was 71.9%.