A comprehensive analysis of available thermodynamic and defect concentration data of the α- and β′-phases in the system Co–Ga is carried out. The β′-phase is analyzed in terms of a model for B2 structures developed recently by Neumann, Chang, and Lee. The disorder parameter obtained from activity measurements, α=3.0×10⁻² at 1173 K, is in good agreement with the one derived from density measurements at the same temperature, α=4.3×10⁻². The temperature dependence of the disorder parameter is found to obey the equation given by the model. The enthalpy of formation of β′-CoGa, calculated from the emf measurements by Katayama, Kemori, and Kozuka agrees within ±5 kJ/g-atom with the results of two calorimetric investigations.

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Measurements of the internal friction Q⁻¹ under tensile loading and the mechanical properties have been carried out for Fe–Co alloys containing 5∼25% Co subjected to annealing at 900∼1200°C. With increasing maximum shear strain amplitude, the value of Q⁻¹ at a frequency of 0.3∼1.1 Hz first increases sharply, goes through a maximum and then decreases gradually. The higher the annealing temperature and the Co content, the greater becomes Q⁻¹. Fe-25% Co alloy exhibits the highest Q⁻¹ value of 75×10⁻³ when annealed at 1200°C for 1 h. With increasing temperature, the Q⁻¹ value decreases from about 400°C, reaches a minimum in the vicinity of 550°C, and sharply increases. Moreover, the Q⁻¹ value decreases rapidly with the magnetic field. The mechanical strength of Fe-Co alloys increases considerably with Co content.

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The premartensitic state of the β–Cu–Zn–Al alloy quenched from high temperature was studied by electron microscopy. The electron diffraction patterns of this alloy were well explained by the model proposed by Takezawa and Sato (J. Japan Inst. Metals, 37 (1973), 793), i.e. by the existence of small particles with an orthorhombic structure. This structure is, however, closely related to the ω-structure.

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The Magnetocrystalline anisotropy constant K_c and the magnetostriction λ_s of a Sendust alloy in composition of 9.6% Si-5.4% Al–bal. Fe are almost equal to zero. Therefore this alloy shows high permeability, but its brittleness makes it hard to roll the alloy. With the object of developing a new alloy having higher permeability and workability, we have studied the effects of the addition of Ni as a fourth element on the magnetic properties of 6% Si-4% Al–bal. Fe alloy showing a second largest value of maximum permeability μ_m in the Fe–Si–Al system.
The experimental results obtained are summarized as follows:
(1) In the 6% Si-4% Al–bal. Fe alloy the addition of 2%–4% Ni makes the coercive force H_c decrease and the maximum permeability μ_m increase considerably.
(2) An alloy with the composition of 3.15% Ni-5.33% Si-4.22% Al–bal. Fe was annealed at 700°C for 1 h in hydrogen and cooled to room temperature at a rate of 1.7°C/s. The magnetic properties obtained were: μ_m=56800, H_c=7.64 A/m, B_r=0.81 T and K_f(B_r⁄B_m)=86.6%.
(3) The effect of magnetic field cooling is striking. By applying a magnetic field 20 Oe during cooling from 700°C to room temperature after annealing at 1250°C for 1 h in hydrogen, the magnetic properties obtained were: μ_m=165000, H_c=2.39 A/m, B_r=0.95 T, B_m=1.09 T and K_f=87.5%.
(4) The value of magnetostriction λ_s, magnetic moment σ_s, Curie point T_θ, electrical resistivity ρ and Vickers hardness Hv of the new alloy were affected considerably by the addition of 2–4% Ni.

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Fe–Cr–Co alloys containing less than 30% chromium and less than 70% cobalt were heated in vacuum over the temperature range of 500∼1000°C for 1 h and then furnace-cooled after cold-drawing by about 98% reduction in area. Measurements of the strain gauge factor and electrical properties at room temperature were carried out for the alloys.
Generally, with increasing annealing temperature, the strain gauge factors of the Fe–Cr–Co alloys decreased gradually to a minimum at about 500°C and increased sharply to a maximum at 800°C. In this system, an Fe-15% Cr-30% Co alloy showed a maximum strain gauge factor of 7.3, and an electrical resistivity of 0.78 μΩm at room temperature and its temperature coefficient of 10.0×10⁻⁴/°C. The thermo-electromotive force relative to copper was −1.2 μV/°C for this alloy.

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The present authors have assumed that the sensitivity of steel to reheat cracking can be most appropriately evaluated by its own plastic deformability.
Based on this assumption, the authors undertook a study of reheat cracking testing of steel by means of the stress relieving test, and of the method for evaluating the sensitivity of steel to reheat cracking.
The results of the study obtained are summaraized as follows:
(1) The reheat cracking test method using the weld thermal-restraint stress and the strain cycle simulator has the advantage in that it allows the test to be made continuously during the heating and holding processes.
(2) Judging from the results of the reheat cracking test using the weld-reinforced test pieces, it is evident that the characteristic phenomena of reheat crackings such as the cracking position, propagation process of cracks, geometry of the cracked fracture surface, and crack initiation temperature coincide with those obtained by others workers.
(3) It is made clear, furthermore, that the sensitivity of steel to reheat cracking may be evaluated from the amount of plastic deformation, Δl_p′ measured at the time of occurrence of cracking.

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In order that the reheat cracking testing of steel by the stress relaxation test may be made in a much simpler and highly reproducible, the present study has probed into the testing conditions for the reheat cracking test of steel with the use of test specimens for the synthetic weld thermal cycle. Also, a method of evaluating sensitivity of steel to reheat cracking with the test specimen for the synthetic weld thermal cycle is also discussed.
The results obtained are summarized as followes:
(1) The effects of the notches in steel and the heating rate on the sensitivity of steel to reheat cracking are remarkable. The sharper notches or slower heating rate lead to the liability of cracking. Consequently, it is necessary to make these factors constant in evaluating the sensitivity to reheat cracking.
(2) Comparison of the results of the reheat cracking test between the test specimens for the synthetic HAZ and the weld reinforced test specimens, shows good correspondense in the cracking phenomenon and cracking sensitivity between the two test specimens.
(3) The reheat cracking test with the test specimen for synthetic HAZ is simple and highly reproducible. Moreover, from the amount of plastic deformation (Δl_p′) at the time of crack initiation, it is possible to evaluate the sensitivity of steel to cracking.

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Die Authoren haben die Einflüss der korngröße auf die Empfindlichkeit der Wiedererhitzungriß der Stahls ausführlich untersucht.
Der Wiedererhitzungs-Rißversuch wurde mit Thermorester-Gerät als Spannungsrelaxationsversuch durchgeführt.
Die Forschungsergebnisse werden wie folgt zusammengefasst:
Der Einfluß der Kristallkorngröße auf die Wiedererhitzungs-Rißempfindlichkeit ist erheblichgroß; mit dem Vergrößeren der Kristallkorngröße erhöht sich die Wiedererhitzungs-Rißempfindlichkeit.

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