Journal of the Society of Materials Science, Japan

Corrosion Problems and Corrosion Monitoring in Chemical Industry

Yoshihisa KAJIYAMA

1986 Volume 35 Issue 388 Pages 1-6
Published: January 15, 1986
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.35.1

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Effect of Tensile Orientation on Stress Corrosion Cracking in SUS 304 Steel Single Crystals

Hitoshi UCHIDA, Keiji KOTERAZAWA, Katsuhiko YOSHIDA, Iwao YAMADA

1986 Volume 35 Issue 388 Pages 7-12
Published: January 15, 1986
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.35.7

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The susceptibility to stress corrosion cracking (SCC) and its oriented crack plane in boiling 42% MgCl₂ solution at 416K were examined in SUS 304 steel single crystals with the tensile axes in five orientations.
The threshold stress to SCC initiation which depended on the tensile axis orientation decreased with increasing Schmid factors in the primary slip system. The threshold stress corresponded to nearly 80% of the 0.2% yield strength (or critical resolved shear stress) in oil at 416K. Many cracks initiated at slip-steps induced by the plastic deformation.
The morphology of fracture also depended on the tensile axis orientation: The single crystals in all orientations except the region near ‹100› tensile axis were characteristic of river-like pattern, which was formed by the crack growth along ‹110› direction on {110} plane. However, the single crystal near ‹100› orientation was characteristic of fan-shaped pattern formed mostly by {100}-‹110› crack growth.
The above results imply that the SCC propagation occurs by the active dissolution of Lomer-Cottrell sessile dislocation in corrosive environment.

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Crack Initiation Behavior of Cyclic SCC under Bending and Torsional Loads in a High-Strength Al-Alloy

Kenjiro KOMAI, Kohji MINOSHIMA, Akinori ICHIKAWA

1986 Volume 35 Issue 388 Pages 13-18
Published: January 15, 1986
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.35.13

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The influences of bending and torsional loading modes on the crack initiation behavior in static and cyclic stress corrosion cracking (SCC) were investigated on a high-strength aluminum alloy sensitive to active path corrosion type SCC. Static and cyclic SCC cracks were found to be initiated under torsional loads as well as under bending loads, and cyclic SCC lives were smaller than those of static SCC irrespective of loading modes. Under bending loads, cyclic SCC cracks in a high stress region were initiated at corrosion pits at three adjacent grain boundaries. In a low stress region, cracks were initiated at longitudinally dissolved trenches along grain boundaries in a similar way to static SCC. Under torsional loads, on one hand, cyclic SCC cracks in a high stress region were initiated at the longitudinal slip dissolution. In a low stress region, the life lines were divided into the longer and the shorter lines according to the types of initiation sites; on the longer life line, cracks were initiated at longitudinal slip dissolution, whereas on the shorter life line, cracks were initiated at the sites including intergranular dissolution. For static SCC, cracks were initiated at longitudinally dissolved trenches along grain boundaries. The longitudinal dissolution along grain boundaries under bending and torsional loads as well as longitudinal slip dissolution under torsional loads is considered to be caused by shear stresses.

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Relationship between Microstructure and Corrosion Fatigue Behavior in a High Strength Steel

Harushige TSUBAKINO, Takeshi SAKAI, Kwang Bae KIM, Koji YAMAKAWA

1986 Volume 35 Issue 388 Pages 19-24
Published: January 15, 1986
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.35.19

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The mechanism of localized corrosion and the initiation of corrosion fatigue cracks were investigated metallographically on HT50-CR steel by testing it with a rotating beam fatigue machine in artificial sea water. Two types of localized corrosion, i.e., pitting and grooving, were observed on the specimen surface. The sites of grooving were restricted to the area which was equivalent to the center region of the received plate. Quantitative metallographic data of pit distribution indicated that the pit growth rate in this area was significantly faster than that in the other area, and many cracks nucleated at the grooving sites. Degenerate or banitic pearlite and elongated inclusions (MnS) were observed in this area. SEM and EPMA examinations showed that the preferential dissolution of ferrite around the degenerate pearlite and MnS resulted in the growth of pitting and grooving corrosion. These inhomogeneous structures in the material had a significant role on the corrosion fatigue life.

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Corrosion Behavior of Aluminum Alloys in Mortar

Yasuyuki TAKATANI, Koji YAMAKAWA, Shiro YOSHIZAWA

1986 Volume 35 Issue 388 Pages 25-29
Published: January 15, 1986
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.35.25

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The corrosion of aluminum alloys in mortar has been studied from the measurements of weight loss and electrochemical characters. In mortar without NaCl, the corrosion of alloys was controlled by the accumulation of corrosion products and its rate was proportional to the passivation current. The corrosion behavior agreed very well with that observed in saturated Ca(OH)₂ solution. On the other hand, the corrosion of alloys in mortar containing NaCl was not controlled by the accumulation of corrosion products. The weight loss of aluminum alloys increased linearly with increasing immersion time and showed the following sequence; Al-Cu>Al-Zn≈Al>Al-Mg>Al-Mn>Al-Mg-Si.

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Corrosion Behavior of Aluminum Alloys in Concrete

Yasuyuki TAKATANI, Koji YAMAKAWA, Shiro YOSHIZAWA

1986 Volume 35 Issue 388 Pages 30-34
Published: January 15, 1986
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.35.30

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The corrosion of aluminum alloys embedded in wet concrete has been studied. All the tested aluminum alloys in concrete without NaCl showed similar weight loss. In concrete containing NaCl, the weight loss showed the following sequence; Al-Cu≈Al-Zn>>Al-Mg>Al-Mn≈Al≈Al-Mg-Si. The corrosion rate of aluminum alloys, except Al-Zn and Al-Cu in concrete with NaCl, was almost proportional to the passivation current and was controlled by the accumulation of corrosion products.

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Solid-State Interfacial Reaction in Molybdenum-Carbide Systems at High Temperature-Pressure, and its Application to Bonding Technique

Akihiro HORIGUCHI, Katsuaki SUGANUMA, Yoshinari MIYAMOTO, Masahiko SHI ...

1986 Volume 35 Issue 388 Pages 35-40
Published: January 15, 1986
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.35.35

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Diffusion couples of molybdenum with several carbides, i.e. SiC, B₄C, TiC, ZrC, HfC and TaC, were heated at various temperatures ranging from 1500 to 1840°C under high pressures of 3GPa and 100MPa for up to 4hr. The couples were then examined for the composition of reaction products, the growth rate of reaction layers, interfacial structures, and tensile strength. In case of Mo-transition metal carbides, Mo₂C layer was mainly formed, so that the carbides, which had supplied carbon, resulted in having the nonstoichiometric composition near the interface. The activation energy for the growth of Mo₂C layer in Mo-TiC system was 332kJ/mol, and that in Mo-TaC system was 366kJ/mol. In Mo-SiC system, Mo₂C layer, the mixed phase of Mo₂C and Mo₅Si₃, and Mo₅Si₃C layer were formed in order from the Mo side. In Mo-B₄C system, the mixed phase of Mo₂B and MoB, and Mo₂BC layer appeared. The decomposed graphite from B₄C was also observed between B₄C and Mo₂BC phase. The activation energy for the growth of total reaction layer in Mo-SiC system was 531kJ/mol, and that in Mo-B₄C system was 183kJ/mol. It can be said that the growth of reaction layers is controlled by diffusion. The orientation of crystals was observed in all reaction products except for Mo₂BC phase in Mo-B₄C system and (Mo, Ta)₂C phase in Mo-TaC system. In HIPed couples, the magnitude of tensile strength was dependent on the difference in thermal expansion coefficient between Mo and carbides. HIPed Mo-TaC couple had the best weldability among the systems examined in the present investigation.

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Microstructure and Mechanical Properties of Al₂O₃, Si₃N₄, SiC, and ZrO₂(PSZ) Ceramics for Slurry Valves

Hisaji MATSUI, Maki KAWAI, Tsutomu TAKAE, Kazuji HASHIMOTO, Shigeru TA ...

1986 Volume 35 Issue 388 Pages 41-47
Published: January 15, 1986
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.35.41

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In order to use ceramics as a material for slurry valves, which are exposed to a flow of slurry containing hard particles of coal or ash, the bending strength of alumina (Al₂O₃), silicon nitride (Si₃N₄), silicon carbide (SiC) and partially stabilized zirconia (PSZ) was examined under the practical condition (400°C, slurry dipped condition). Also high resolution transmission electron microscopy (HR-TEM) was employed to characterize these materials. From the direct observation of the microstructure of cracked surfaces, it was shown that fracture took place from the structual weak points, that is, pores, large crystal grains and the impurity phases. In the case of ceramics with uniformly small crystalline particles and very little pores, fracture seems to occur through the impurity phases.

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A Model for Evaluating Strength and Fracture Toughness of Structural Ceramics

Kimiaki NAKAKADO, Ichiro TAKAHASHI, Hiroshi MIYATA

1986 Volume 35 Issue 388 Pages 48-53
Published: January 15, 1986
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.35.48

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In order to elucidate the notch width or notch root radius dependence of the critical stress intensity factor evaluated by SENB (Single Edge Notched Beam) specimens, 4-point bending tests were carried out on hot-pressed SiC (with 2wt% AlN) and sintered Si₃N₄. The Experimental results showed that the critical stress intensity factor K_c determined with SENB specimens coincides with a valid fracture toughness K_Ic value only when notch root radius ρ is smaller than about 10μm. For larger root radii, the variation of K_c with ρ was observed, and this can not be attributed only to the stress concentration effect of notch.
In the present study, by introducing a micro-damage concept a method was proposed for evaluating K_Ic from K_c values given by SENB specimens having rather blunt notch.
On the basis of the published strength data for SiC, the relation between strength and microstructure was examined. It was assumed that a micro-damage existed at the machine finished surface, and its size should be the sum of the machined damage depth h_max and the maximum grain diameter d_max. Here, h_max can be estimated from the average grit size of the diamond disk used. An analysis was made of the dependence of K_c on ρ by considering the micro-damage at the notch root, and a theoretical expression was formulated. The experimentally observed K_c-ρ relation agreed quite well with the theoretical prediction.

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Submicron Grinding of BaTiO₃ by Ball Milling

Kenji TANAKA, Kichi MINAI, Kikuo WAKINO, Isao UEI

1986 Volume 35 Issue 388 Pages 54-58
Published: January 15, 1986
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.35.54

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Submicron grinding of BaTiO₃ powder was studied by a ball mill with small alumina balls of 0.75mmφ to 30mmφ. BaTiO₃ clinker which was obtained by calcining equimolar of TiO₂ and BaCO₃ was preground to 1.8μm. Submicron grinding of the BaTiO₃ powder was possible by ball milling with several mmφ balls. In the case of ball diameter of 2mm, the specific surface area was maximum.
An attempt was made to represent the specific surface area in terms of volume per ball and total surface area of used balls, and the following experimental equation with a time term was obtained.
ln(SS)=-0.247lnr³-0.738/r+0.429lnt+1.57 where SS is the specific surface area, r is the ball radius and t is time. The multiple correlation coefficient R was found to be 0.982 when calculated by a computer.

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Crack Growth and Phase Transformation in Partially Stabilized Zirconia

Naohiro SOGA, Takeshi SHIONO

1986 Volume 35 Issue 388 Pages 59-65
Published: January 15, 1986
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.35.59

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In order to clarify the dependence of crack growth on phase transformation and the effect of stress on phase transformation in partially stabilized zirconia, the hardness and fracture toughness of tetragonal zirconia polycrystalline specimens containing 3mol% Y₂O₃ (the average grain size of 0.3-0.4μm) were measured as a function of indenting load by using the Vickers indentation method. The fracture energy was obtained by the single edge notched beam method at various strain rates and by the work of fracture method. The same measurements were performed also on the specimens heat treated at different temperatures in which a part of tetragonal phase transformed to the monoclinic phase. Furthermore, the degree of phase transformation at 300°C was determined as a function of time and bending stress. The results obtained are summarized as follows:
(1) All the specimens with or without heat treatment had almost the same hardness of about 12GPa, although a slight decreasing tendency with increasing load was observed. They also showed a similar tendency in fracture toughness except that the untreated specimen showed very high toughness when indented at low loads of less than 200N.
(2) The K_Ic obtained by SENB method increased with increasing stress rate in the range above 10^-2mm/min, but remained almost constant at the stress rate lower than 10^-2mm/min. This seems to indicate that some threshold stress exists to start slow crack growth in tetragonal zirconia.
(3) The fracture energy obtained by SENB method was several times larger than that of WOF method. Since the former reflects the energy needed to start the fracture rather than the energy needed to make a new fracture surface, a very large energy is spent to start crack growth, probably due to the phase transformation.
(4) The phase transformation was enhanced by the residual stress around the Vickers indent when heat-treated at 300°C. This stress induced transformation becomes apparent when the tensile stress exceeds 450MPa.

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Fracture Toughness of LiF Single Crystal

Kunio HAYASHI, Masao NOMURA, Tomozo NISHIKAWA

1986 Volume 35 Issue 388 Pages 66-72
Published: January 15, 1986
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.35.66

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The fracture toughness (K_Ic) of LiF single crystal was evaluated by the indentation microfracture technique (IMT) and the indentation strength technique (IST) at room temperature. The indentation crack on the (001) of ‹100› specimen resulted in the lowest K_Ic of about 0.5MNm^-1.5 in both IMT and IST because the {110} is the preferred cleavage plane of this crystal. The Vickers hardness (H_V) for the (001) was obtained to be about 0.9GPa. A fairly smooth planar was provided by the crack-propagation originated from the initial crack on the (001) of ‹110› specimen. However, cracks in the ‹110› (110) specimen became eventually angled at 45° to the original flaw. As the result, K_Ic≈0.7MNm^-1.5, H_V≈0.9GPa for the former, and K_Ic≈0.8MNm^-1.5, H_V≈1.2GPa for the latter. The indentation crack on both the (110) and (112) of ‹111› specimen didn't propagate along the extention of Vickers indentation diagonal and produced the rough surface after fracture. The K_Ic values for ‹111› (110) and ‹111› (112) were determined to be 1.5 and 1.8MNm^-1.5, respectively, while H_V≈1GPa. These results indicate that the K_Ic of single crystals is affected by the cleavability of crystals and the geometric configuration between the cleavage plane and the direction of crack propagation.

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Preparation and Properties of Binary Oxide Glasses Containing Rare Earth Oxides

Hiromitsu KOZUKA, Rikuo OTA, Naohiro SOGA

1986 Volume 35 Issue 388 Pages 73-79
Published: January 15, 1986
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.35.73

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Thermal image furnace melting and twin-roller quenching were used to prepare glasses containing large amounts of rare earth oxides in Ln₂O₃-M_XO_Y systems (Ln₂O₃=La₂O₃, Nd₂O₃, Y₂O₃; M_XO_Y=SiO₂, Al₂O₃, TiO₂, Nb₂O₅).
The glass-forming regions were found at the following compositions close to the eutectic points of the phase diagrams: (20-30)Ln₂O₃-(70-80)SiO₂, 60Ln₂O₃-40SiO₂, 20Ln₂O₃-80Al₂O₃, 20Ln₂O₃-80 TiO₂, (20-30)Ln₂O₃-(70-80)Nb₂O₅ and 60Ln₂O₃-40Nb₂O₅. The glass transition temperature T_g was determined by DTA. All the glasses showed high glass transition temperatures over 700°C. Although T_g increased or decreased with Ln₂O₃ content depending upon the system, the change was linear with Ln₂O₃ content around the eutectic compositions. This seems to indicate that there is no peculiar behavior of viscosity itself at the eutectic compositions. The liquidus viscosity becomes the maximum at the eutectic compositions due to low liquidus temperatures, which makes glass-formation easier at the eutectic compositions.
A glass model consisting of four-coordinated aluminum units was proposed for Ln₂O₃-Al₂O₃ glasses based on the results of IR spectra and observed AlKα chemical shifts. On the other hand IR spectra of Ln₂O₃-TiO₂ glasses showed a mixture of six- and four-coordinated titanium units.
Visible and ultraviolet absoption spectra of Nd³⁺ were studied on Nd₂O₃-M_XO_Y glasses. The peak positions of these absorption bands moved towards lower wave numbers linearly with increasing compositional basicity of the glasses. Their color changed from purple-like blue to green-like blue, as the absorption bands shifted towards lower wave numbers.

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Impact Problem and its Applications

6. Generation of Dynamic High Pressure and ist Application

K. Kani

1986 Volume 35 Issue 388 Pages 80-86
Published: January 15, 1986
Released on J-STAGE: June 03, 2009

DOIhttps://doi.org/10.2472/jsms.35.80

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