The effects of rolling temperature on the mechanical properties of mild steels are expected to be complicated due to the combined effects of recovery and recrystallization of austenite.
In order to clarify these effects under certain conditions, mechanical properties and microstructures of a low carbon steel and a weldable high strength steel were investigated using transmission electron microscopy.
The results were as follows:
(1) The ferrite grain size of a low carbon steel decreased with decreasing rolling temperature insofar as it was deformed in the austenite region, but no change was observed in the dislocation structures. The rolling after the γ→α transformation increased the dislocation density.
(2) The microstructures of a high strength steel varied complicatedly, probably due to the recovery and recrystallization of austenite.
(3) The yield stress depended on the grain size and dislocation density of ferrite.
(4) The ferrite grain size, shapes of grain and dislocation structures would affect the Charpy impact properties.

View full abstract

A series of experiment were programmed on the effect of ultrasonic vibration on the compressive deformation of metals. For this purpose, an apparatus has been devised. In this report, the outline of the apparatus and some analytical results of various factors involved are given.
The ultrasonic vibration is generated by a magnetostrictive nickel transducer, and is superimposed on a static compressive load through horns in the form of resonance oscillation. The frequency and the amplitude transferred to a specimen are about 22 KC and up to about 17 μ, respectively. Analysis has been made for the factors, which would affect the vibration mode or the deformation behaviour, such as specimen size, static load, vibrational stress, amplitude, acceleration and heat generation, etc. Some data of a preliminary experiment are also described.

View full abstract

Using the apparatus described in the preceding report, the effects of superimposed ultrasonic vibration on compressive deformation were investigated with several materials. The flow stress of compression can be reduced by superimposing the vibration. However, the effectiveness differs with the kind of specimen, being related to the characteristics of materials such as the acoustic impedance, Young’s modulus, melting point, work-hardenability and stacking-fault energy. With increasing amplitude of vibration, the rise of temperature becomes more remarkable, but it shows material dependence. The hardness distribution of the worked piece is also influenced by the vibration.

View full abstract

Substructures of the martensite in quenched commercially pure titanium have been examined by means of transmission electron microscopy. The result is that the martensite crystal has three kinds of lattice defect: internal twins, stacking faults and dislocations. The twinning plane of the internal twins is {10\bar11}. The twin of this kind has so far been observed in case of the deformation of α-Ti. It is therefore thought that the {10\bar11} twin is produced by the martensite transformation but not by the accompanying stress. The stacking faults and dislocations are found on (0001) planes of both the matrix and the internal twins of the martensite crystal.

View full abstract

{10\bar11} transformation twins, produced in the martensite of commercially pure titanium, have been investigated by means of transmission electron microscopy and discussed in relation to the character of the martensitic transformation. The results are as follows: (1) The twins have a thickness of 250∼3000 Å, and they are different in appearance from those of the martensite of ferrous alloys. (2) The incoherent boundary of those twins was found to be (12\bar31), (0\bar223), or (11\bar20). From the angles between the coherent boundaries composing nodes, it is concluded that these boundaries cannot exist in thermal equilibrium, and consequently they show configurations resulting from the martensitic transformation. (3) It is considered that the (\bar1011) twin plane has come from (101)_β of the matrix, and therefore the twin plane must have played an important role in the transformation.

View full abstract

Behaviours of the precipitates and hardness in the heat-affected zone of 17–4 PH stainless steel were investigated. The heat-affected zone was obtained by single bead welding using a TIG arc method, in which a single bead 10 cm in length was placed on the 17–4 PH stainless steel plate of 20×50×200 mm³. To analyze the precipitates and the hardness distribution in the heat-affected zone, the specimen, 15 mm in length and 5 mm in diameter, was rapidly heated and cooled by the reproducing weld thermal cycle apparatus using a high-frequency induction heating. The hardness of the specimen subjected to the thermal cycle by the reproducing weld thermal cycle apparatus was compared with the hardness in the heat-affected zone subjected to the weld thermal cycle under TIG arc welding. The results may be surmarized as follows:
(1) In the heat-affected zone of 17–4 PH stainless steel solution treated, the maximum hardness was obtained at about 600°C, and this temperature was about 100°C higher than that of ordinary precipitation treatment. The higher the precipitation temperature, the lower became the maximum hardness with increasing precipitation time.
(2) In the base metals subjected to the reproducing weld thermal cycle at a peak temperature of 650°C prior to the precipitation treatment, there appeared some parts which were not hardened by the precipitation treatment. The softening temperature by the weld thermal cycles in the heat-affected zone of the base metal subjected to the precipitation treatment ranged from 650° to 900°C, and the solid solutioning was fully accomplished at a temperature above 900°C.

View full abstract

The purpose of this research is to examine the effects of melting conditions and mechanical properties of the specimens, which were cast into the green sand mould of 20-mm diameter, on the evaluation for the quality of flake graphite cast iron. Furthermore, the relation between chemical composition and deflection on the evaluation values for quality was examined on the as-cast specimens. The results obtained are summarized as follows:
(1) On the quality evaluation, the Reifegrad (RG), the relative bending load (RB), the relative hardness (RH) and the relative hardness related to the bending load (RH_b) of the cast iron prepared by reducing-refining melting are superior to those of the cast irons prepared by non-reducing refining melting.
(2) From the standpoint of the quality evaluation, the ranges of most suitable chemical composition for the cast irons prepared by the reducing-refining melting are as follows:
Total Carbon 2.90∼3.50% Silicon 1.75∼2.23% Manganese 0.72∼0.84% Phosphorus 0.064∼0.120%
Sulfur 0.020∼0.150% Oxygen 9∼30 ppm
(3) The suitable chemical compositions of the cast irons prepared by nonreducing-refining melting are within the bounds of the following ranges:
Total Carbon 3.05∼3.10% Silicon 1.30∼1.36% Manganese 0.84∼0.88% Phosphorus 0.10%
Sulfur 0.023∼0.026%
(4) The relation between quality evaluation values and deflection was investigated, and the following equations which may explain the values of deflection (D) were obtained:
RB=40.33+14.46D, RH_b=1.385−0.088D.

View full abstract

Stress corrosion behaviours of austenitic stainless steels containing various contents of nitrogen and of Inconel were investigated using thin-foil and bulk specimens.
The mode of micro-attack in thin-foil specimens of nitrogen-rich stainless steel in a 3% NaCl aqueous solution (pH 1.6) at room temperature and of Inconel in a boiling 42% MgCl₂ aqueous solution was almost the same as that for nitrogen-rich stainless steel in a boiling 42% MgCl₂ aqueous solution. Stress corrosion behaviours of bulk specimens observed by the replica technique indicated that at the initial stage of corrosion no difference was recognized in the nucleation of micro-attack in all the cases, but with increase in exposure time there appeared a remarkable difference in the corrosion behaviours depending on the relative difficulty of the cracking conditions. In a nitrogen-rich stainless steel aged at 200°C after deformation, the segregation and precipitation were recognized in both the transmission electron microscope observations and the constant strain rate stress-strain relations.
From these results, it seems that the segregation of solute atoms is particularly necessary for the propagation of stress corrosion cracking in austenitic stainless steels, and that the nucleation and propagation of cracking have different mechanisms.

View full abstract

The mechanism of intergranular stress corrosion cracking in 70 Cu–30 Zn alloy was investigated by means of electron microscopy, electron diffraction and stress corrosion cracking tests using Mattsson’s solutions (0.05 M/L CuSO₄+0.5M/L (NH₄)₂SO₄) at pH values of 2.0, 7.4 and 10.0. It was found from the stress corrosion cracking tests that, at pH 7.4 a Cu₂O surface film was formed on the brass and intergranular cracks occurred easily, but at pH values of 2.0 and 10.0, the brass was unsusceptible to cracking. The observation of bulk specimens by a replica technique indicated that at pH 7.4 micro-attacks initially nucleated within grains but two hours later corrosion was remarkably promoted in grain boundaries. Although the corrosion behaviours of bulk specimens depended considerably on pH values, the mode of micro-attack nucleation in thin-foil specimens did not change with pH values, but the preferential micro-dissolution in the slip steps was predominant. At pH 7.4 micro-pits formed in the slip steps consisted of Cu₂O and Cu layers which were cathodic to the brass substrate, so that the brass surface was covered with these layers. As the Cu₂O and Cu layers would lock the movement of dislocations on emergent slip planes within grains the absorption of dislocations and vacancies in grain boundaries would increase. In consequence, the chemical reaction in the grain boundaries would be accelerated than that in the case of no surface film layers, and the path of cracks would be formed in the grain boundaries.

View full abstract

The effects of the binder composition in the cemented carbides have been investigated, and it is known that the binder composition or the carbon content of the alloys has a remarkable effect on the properties of the two-phase WC–Co alloys. However, no research has so far been carried out on WC–TiC–Co alloys.
In the present experiment, ordinary WC–TiC–10% Co alloys which contain 6∼25% titanium carbide in carbides and consist of (WC+β+γ) three phases were vacuum-sintered. The carbon contents of the specimens were strictly controlled. The relation between the properties of the sintered alloys and the carbon content or the titanium carbide content was examined. The results obtained were as follows: (1) The lattice parameters of the γ and β phases showed a regular change in the three-phase region due to the change in composition in both phases. (2) The tungsten content in the binder phase of the three phase alloys varied from 2∼3% in minimum to 9∼10% in maximum depending on the carbon content. The amount of tangsten dissolved in the binder phase corresponded to the values in the WC–Co alloys. (3) The addition of titanium carbide resulted in an extreme extension of the three phase range owing to the change in carbon content in the β phase. (4) The properties, such as transverse-rupture strength, magnetic saturation, etc., varied regularly within the three-phase region.

View full abstract

The diffusion coefficients of silver in the lead-tin system have been studied at various concentrations of tin N_Sn, 223, 0.405, 0.614 and 0.799, and over the temperature ranges of 410°∼557°C, 453°∼609°C, 391°∼609°C and 405°∼690°C, respectively. The results can be represented by the equations:
D_Ag in Pb–Sn(N_Sn=0.223)=(2.89±0.26)×10⁻⁴exp{−(3090±130)⁄RT}cm²⁄sec,
D_Ag in Pb–Sn(N_Sn=0.405)=(2.79±0.26)×10⁻⁴exp{−(2980±140)⁄RT}cm²⁄sec,
D_Ag in Pb–Sn(N_Sn=0.614)=(2.46±0.17)×10⁻⁴exp{−(2720±100)⁄RT}cm²⁄sec,
D_Ag in Pb–Sn(N_Sn=0.799)=(5.43±0.34)×10⁻⁴exp{−(3780±90)⁄RT}cm²⁄sec.
With the aid of thermodynamic properties of the Pb–Sn systems and supposing
D_i(Ag)≈D_i(Sn),
the diffusion coefficients of tin in the Pb–Sn system at 500°C have been calculated by the equation
D_Sn in Pb–Sn=D_i(Sn) in Pb–Sn(1+dlnγ_Sn⁄dlnN_Sn)
≈D_i(Ag) in Pb–Sn–Ag(1+dlnγ_Sn⁄dlnN_Sn).
The calculated values of diffusion coefficients at various compositions agree well with those experimentally obtained in a previous study.

View full abstract

The diffusion coefficients of silver, D_Ag, in molten lead-bismuth and tin-bismuth alloys have been measured over the temperature ranges from 420° to 623°C and from 439° to 628°C, respectively, using the capillary method and Ag¹¹⁰ as the radioactive tracer.
The results can be represented by
D_Ag in Pb–Bi(N_Bi=0.202)=(2.34±0.19)×10⁻⁴exp(−(2830±120)⁄RT),
D_Ag in Pb–Bi(N_Bi=0.438)=(3.58±0.27)×10⁻⁴exp(−(3240±110)⁄RT),
D_Ag in Pb–Bi(N_Bi=0.606)=(6.95±0.90)×10⁻⁴exp(−(4180±180)⁄RT),
D_Ag in Sn–Bi(N_Bi=0.207)=(7.52±0.60)×10⁻⁴exp(−(4170±120)⁄RT),
D_Ag in Sn–Bi(N_Bi=0.377)=(7.24±0.63)×10⁻⁴exp(−(4020±130)⁄RT) and
D_Ag in Sn–Bi(N_Bi=0.584)=(6.84±0.46)×10⁻⁴exp(−(3910±110)⁄RT).
Using these results, the diffusion coefficients of bismuth, D_Bi, in molten lead-bismuth and tin-bismuth alloys can be calculated from the following equations:
D_Bi in Pb–Bi≈D_Ag in Pb–Bi(1+dlnγ_Bi⁄dlnN_Bi).
D_Bi in Sn–Bi≈D_Ag in Sn–Bi(1+dlnγ_Bi⁄dlnN_Bi).
The obtained results are in agreement with the previous experimental data within the experimental error.

View full abstract