In a Ti–15V–3Cr–3Sn–3Al alloy, the internal structure of {332}⟨113⟩ deformation twins formed by weak rolling at 77 K was studied by means of transmission electron microscopy. {332}⟨113⟩ deformation twins accompany very characteristic dislocation loops attached to the twin/matrix interface in the matrix. Inside the twin, a parallel array of stressinduced ω plates with a single variant are formed. It is considered that such dislocation loops are expelled from the β twin/ω interface into the β matrix during the shrinkage of twins by unloading. Secondary {332}⟨113⟩ twinning occurs in the primary twins by further deformation.

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Recrystallization in boron-free Ni₃Al single crystals with a near ⟨111⟩ tensile direction, which were deformed in tension to a strain of 20% at room temperature, was investigated through the observations of optical micrographs and composition images in SEM and the orientational analysis of ECPs. Four kinds of slip bands on different {111} slip planes appear. After annealing, most of recrystallized grains have the rotation relations with the deformed matrix about ⟨110⟩, ⟨111⟩ or ⟨100⟩ axis. Moreover, there are coincidence boundaries with Σ 3 to Σ 19 between the recrystallized grains and the deformed matrix. A large number of recrystallized grains possess the ⟨110⟩ rotation relation. The ⟨110⟩ and ⟨100⟩ rotation mechanisms for the formation of recrystallized grains in Ni₃Al are suggested.

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Nucleation kinetics of proeutectoid ferrite allotriomorphs at austenite grain boundaries were measured in Fe-0.1 mass%C and Fe-0.1 mass%C-2 mass%Mn alloys with small amounts of V or Nb. Nb was one or two orders of magnitude more effective than V in reducing the nucleation kinetics of ferrite compared at the same amount of addition. The segregation of alloying elements to austenite grain boundaries and the formation of atom clusters with carbon or fine coherent precipitates at ferrite nucleation sites were considered as possible causes for the observed suppression of nucleation. However, quantitative agreement with theory or direct experimental evidence is yet to be obtained for these possibilities to be deemed operative in the present alloys.

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Reactive diffusion of the Ni–Si system has been studied by using bulk Ni/bulk Si single crystal diffusion couples in the temperature range from 823 to 1023 K. The results were compared with the previous experimental results obtained by using Ni thin film/bulk Si diffusion couples.
In the bulk diffusion couples annealed more than 3.6 ks, Ni₅Si₂, Ni₂Si, Ni₃Si₂ and NiSi were found. The silicides formed in the bulk diffusion couple grew satisfying the parabolic law and square of growth rate, k², of Ni₂Si could be expressed by the following equation:
k²=3.21×10⁻⁷exp(154kJ⁄RT)(m²⁄s).
The value k² obtained by extrapolating the above equation to the lower temperatures ranging from 523 to 603 K is 1⁄10²∼1⁄10⁴ times smaller than the values for Ni₂Si formed in the thin diffusion couples in the temperature range. However, the values of interdiffusion coefficients for the thin couples and bulk couples agree well with each other. The reason for the difference in k² between the thin and bulk samples can be atrributed to the difference of phase layers which are adjacent to the Ni₂Si phase and not to the fast diffusion such as grain boundary diffusion in the thin film diffusion couples.

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An attempt has been made to optimize the solutionizing temperature and duration by observing microstructural changes along with physical and mechanical properties of a hypoeutectic Al–Si (BS LM16) alloy. The specimens were solutionized over a range of temperatures (763, 778, 793, 813 and 833 K) and duration.
Solutionizing at 763, 778 and 793 K revealed significant morphological changes in the microconstituents while the specimens at 813 and 833 K suffered from partial melting. The former group of temperatures offered significant improvement in physical and mechanical properties of the alloy while the latter one caused deterioration in properties. Coarsening of phases was found to cause a reduction in hardness, density, strength and ductility of the alloy beyond certain solutionizing duration at 763, 778 and 793 K.
The resolidified regions, where partial melting had occurred as a result of solutionizing at 813 and 833 K, possessed significantly higher hardness resulting from their refined microstructure as compared to the unaffected part of the specimens. Inspite of this, the specimens suffered from deterioration in their overall hardness due to the formation of secondary porosity and microcracking. Reduced density, strength and ductility and increased electrical resistivity of the alloy also agreed well with the generation of porosity and microcracks at these temperatures. The positive influence of increased hardness and refined microstructure of the resolidified regions seemed to have been outweighed by the predominant ill-effects of the porosity and microcracking as observed by the deterioration in the properties of the alloy at 813 and 833 K.
The study indicated that solutionizing the alloy in the temperature range of 778–793 K for 2–8 h offers spheroidized constituents and improved properties which can exhibit good results during its ageing.

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Critical partial pressures of water vapor and hydrogen gas, which caused brittle fracture at room temperature, were measured for Co₃Ti intermetallic compounds. The critical partial pressures significantly depend on deformation rate and alloy composition. The critical water vapor pressure (P_H2O^*) of a Co-21mol%Ti alloy is measured to be 0.1 Pa at a deformation rate of 0.2 mm/min. With increasing deformation rate, the P_H2O^* increases. In a Co-23 mol%Ti alloy, P_H2O^* is about four order of magnitude lower than that of a Co-21 mol%Ti alloy, indicating that the former is more susceptible to the embrittlement in air than the later. The critical hydrogen gas pressures (P_H2^*) of these two alloys are lower than the P_H2O^*, which indicates that these alloys are more susceptible to the embrittlement in hydrogen gas than in air. The difference in susceptibility between these alloys is attributed to the difference in intrinsic grain boundary strength. Environmental embrittlement of Co-21 mol%Ti is completely suppressed by an addition of 3mol%Fe, and the P_H2O^* is evaluated to be larger than 1 kPa, while the P_H2^* is measured to be 2 Pa at a deformation rate of 0.2 mm/min. It is considered that decomposition rate of water vapor is reduced by the addition of iron, resulting in the suppression of the embrittlement in air. It is proposed that higher susceptibility to environmental embrittlement of Co₃Ti intermetallic compounds than that of high strength steels is due to the acceleration of decomposition of water vapor at the surface of the intermetallic compounds.

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The objective of the present study is to investigate the effects of fine precipitates of vanadium nitride (VN) on the creep deformation behavior of 12%Ce-15%Mn austenitic steels through the measurement of internal stress and effective stress. These stresses are obtained by strain dip test. The internal stress of VN free materials was unequivocally determined as a function of applied stress. On the other hand, the change of deformation rate during the strain dip test of the VN containing materials was very small and could not be detected in a range of reduced applied stress. Consequently, the internal stress and effective stress of VN containing material showed a band range of values as a function of applied stress. This range indicates that fine and dense precipitates of VN become strong barriers to the dislocation motion in a wide variation of stresses worked on the dislocations. The temperature dependence of internal and effective stresses of the VN containing material was also clarified. The difference between the stress dependence of minimum creep rate at the lower applied stress and that at the higher one was also discussed to be caused by the behavior of internal and effective stresses.

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Cast duplex stainless steel of CF3M was aged at 450°C for up to 10000 h. The ferritic phase was hardened and embrittled by the ageing. Cyclic polarization curves were measured in 0.5 kmol/m³ H₂SO₄+0.01kmol⁄m^3KSCNsolutiontoinvestigatetheelectrochemicalbehaviourduringphasedecompositionoftheferriticphase.Inaddition,the3−Dmicrochemicalchangewasexaminedbyarecentlybuiltpositionsensitiveatomprobe(POSAP).Thereactivationcurrentpeakappearsinthecyclicpolarizationmeasurementafter400hageing.Thisresultsfromthedissolutionofthechromium−depletediron−richregionformedduringdecompositionoftheferriticphase.
ThePOSAPanalysisofthe10000hagedsteelshowsawell−developedphasedecompositionintothechromium−richandiron−richregionsinseveralnanometerscale.Flatplate−likechromium−richregions(Cr≥50at%)ofafewnanometerthicknessareobservedataspacingofafewnanometer,whiletheiron−richregions(Cr<12at%)formthepercolatedstructuresurroundingtheflatplate−likechromium−richregions.

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The diffusion coefficients of the green and violet isomers of Cr₂(SO₄)₃ in water and acidic solutions were measured at 298 K by using a diaphragm-cell method. These data were determined as a function of concentration of solute, and analyzed in terms of the diffusion potential gradient and changes in the mean activity coefficient and viscosity. The diffusion coefficients of violet Cr₂(SO₄)₃ are larger than those of green Cr₂(SO₄)₃ at the same molar concentration, and the two sets of D values demonstrate different concentration dependencies. The results can be understood in terms of the mean activity coefficient of Cr₂(SO₄)₃, which is of larger magnitude for violet Cr₂(SO₄)₃ solution and is more dependent on salt concentration. The presence of H₂SO₄ in large amounts, for example 2 kmol·m⁻³, is found to decrease both the green and violet Cr₂(SO₄)₃ diffusion coefficients. At lower concentrations of acid, there is a slight increase in D values. The effect of acid is to modify the diffusion potential, as well as the mean activity coefficients of Cr₂(SO₄)₃ and the viscosity of solution. Finally, compared with other metal sulphate systems previously investigated, both the green and violet isomers of Cr₂(SO₄)₃ exhibit smaller diffusion coefficients than those of the 2-2 electrolytes (Cu, Ni, Zn) and Fe₂(SO₄)₃.

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The crack susceptibility and properties of AlN to copper joints brazed with the Ag-27 mass%Cu-2%Ti filler metal and the Sn-38 mass%Pb solder were investigated. The heat conduction analysis suggested that the thermal conductivities of AlN-copper joints using the Ag–Cu–Ti insert metal added to tungsten interlayer and using the Sn–Pb solder with a thickness of less than 0.5 mm exceeded that of the AlN substrate (180 W/m·K). Thermal stress distribution in the AlN-copper joints was numerically calculated by a finite element method. The calculated maximum principal stress in AlN reduced by the use of a soft insert layer and/or a low expansivity interlayer. The crackings of brazed joints could be prevented when the tungsten interlayer thickness exceeded 0.8 mm in the brazed joint, and when the Sn–Pb solder was employed during the bonding operation. The tensile strength of the AlN-copper joints brazed at 1078 K for 120 s added to the 1.0 mm thick tungsten interlayer reached about 50 MPa, and that of the metallized AlN-copper soldered joints was about 20 MPa. The superior reliability for thermal cycling and heat conduction could be obtained for the AlN-W-copper joints using the Ag–Cu–Ti filler metal and titanium-copper multilayer-metallized AlN-copper joints using Sn–Pb solder.

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Possibility of the exchange-spring magnets in the Sm–Fe–(C, N) system has been studied by preparing the microduplex structure consisting of a nanocrystalline soft magnetic α-Fe phase and a hard magnetic Sm₂Fe₁₇(C, N)_x phase. In this study, the microduplex structure was prepared by annealing the melt-spun ribbons in the amorphous state. The magnetic properties of annealed Sm_yFe_95−yC₅ (y=5−10) ribbons after nitriding, whose Sm contents were lower than the stoichiometric composition of Sm₂Fe₁₇C, were investigated in correlation to their microstructures. In the as-spun state, Sm₇₋₁₀Fe₈₅₋₈₈C₅ (y=7−10) ribbons consist only of the amorphous phase, while in the Sm₅Fe₉₀C₅ (y=5) and Sm₆Fe₈₉C₅ (y=6) ribbons an α-Fe phase is also observed. The α-Fe phase in the ribbons with y=5 and 6 can be formed by the crystallization during melt-quenching. In all cases, the amorphous phase disappears after the annealing above 600°C, resulting in the microduplex structure with α-Fe and Sm₂Fe₁₇C_x phases. Relatively high coercivities were observed in the Sm₇₋₁₀Fe₈₅₋₈₈C₅ ribbons after annealing and subsequent nitriding. Especially, the Sm₇Fe₈₈C₅ ribbon annealed at 600°C for 5 min and subsequently nitrided at 450°C for 4 h exhibits the coercivity of 269 kAm⁻¹ with the maximum energy product of 70.1 kJm⁻³.

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A bulk amorphous Zr₆₀Al₁₀Ni₁₀Cu₁₅Pd₅ alloy was prepared by the zone melting method using an arc-type heat source. The bulk amorphous alloy prepared on the copper hearth has a rectangular parallelepiped shape with a thickness of 10 mm, a width of 12 mm and a length of 170 mm. A majority of the region except the bottom and side edge regions contacted with copper hearth consists of an amorphous phase. The cooling rate achieved by the zone melting method is high enough to cause an amorphous phase in the Zr-based alloy where heterogeneous nucleation is suppressed. The amorphous phase subjected to continuous heating exhibits a distinct glass transition, followed by a wide supercooled liquid region and then an exothermic peak due to crystallization. The success of producing the bulk amorphous alloys by the zone melting method implies the possibility of the continuous production of the bulk amorphous alloys and seems to accelerate the subsequent progress of amorphous alloys.

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