Kohsuke Tagashira

Texture in hot rolled austenite and resulting transformation products

Abstract By making use of a commercially processed TRIP (transformation induced plasticity) steel it was possible to directly measure the texture of hot rolled low alloyed austenite from the traces of retained austenite (9%) remaining at room temperature. This texture was used as the basis for analysing preferred orientation of the transformation products, ferrite and bainite, in the same steel. The EBSP (electron back scattering patterns) method was employed to determine textures of the different phases. The austenite condition was shown to be partially recrystallised, having a β -fibre texture in the deformed structure and a spread from cube to Goss in the recrystallised regions The polygonal ferrite and bainite textures have many similarities but also some differences, being significantly stronger in the bainite, especially the 100〈011〉 component. A model is presented which explains quite well the transformation texture based on the orientation relationship between austenite and ferrite. Where appropriate, variant selectivity is incorporated by reference to accepted theories of phase transformations in steels. Both nucleation and growth are considered to play roles in defining transformation textures, depending on the physical processes which are involved.

Wear resistance and microstructure of cryogenic treated Fe-1.4Cr-1C bearing steel

Wear processes greatly reduce precision and the service duration of bearings. Subzero treating techniques have been used to improve wear resistance of materials for many years. In the previous paper, the authors definitively divided the subzero treatment into a cold treatment and a cryogenic treatment according to the negative treating temperature. It is widely accepted that cold treating temperature is sufficient to fully transform any retained austenite into martensite which is considered to be a major factor to improve wear resistance. However, more recent evidence has shown that wear resistance is further enhanced by a cryogenic treatment. Despite the numerous practical successes of a subzero treatment and research projects undertaken worldwide, no conclusive metallurgical understanding on this treatment has been established. In this paper, the wear resistance and microstructure of a bearing steel resulting from cold and cryogenic treatments is studied.

The interpretation of polarization curves for Al-Fe alloys in de-aerated NaCl solution

An attempt is made to explain the experimental evidence that the peak value of anodic current density, imax, occurs at −0.75 V (Ag/AgCl) in the polarization of Al-Fe alloys in de-aerated 0.1 M NaCl solution. It was found that this can be explained in terms of the anodic reaction which is the oxidation of iron in FeAl3 to ferrous hydroxide, Fe(OH)2. The iron formed as intermetallic compounds in Al-Fe alloys does not always provide an insoluble cathode in the aluminum matrix, but changes from iron into Fe(OH)2 under suitable solution conditions.

Study of the comet-shaped carbides in the uppermost surface layer of bearings

Abstract The structure of the uppermost surface layer for commercial bearings with poor grinding procedures has been studied by means of transmission electron microscopy, electron probe X-ray microanalysis and Auger electron spectroscopy methods. It was found that a new etching-resistant phase with a comet shape appeared, which was identified by structure analysis as being (Cr, Fe) 7 C 3 carbides. We supposed the formation of the new etching-resistant phase was due to the grinding heat and grinding force.

The Effect of Carbon Content in Filling Alloys on η Phase Formation in the Interface Zone of YG30 and Weld Bead

The cemented carbide YG30 and steel 1045 were welded with Co-Fe-C filling alloys with different carbon contents by the tungsten-inert-gas (TIG) arc welding. η phase formation at the welding joints was investigated through scanning electronic microscopy (SEM). The results show that the average composition of η phase is W-25, Fe-22, Co-19, C-24 (mass, %), which is a kind of carbide enriched by Fe, W，and Co. The amount of η phase formed near the interface of YG30 and weld bead is related to the C content in the filling alloy. Namely the amount of η phase decreases with the increasing of the C content in the filling metal. When the C content reaches to 0.8 wt%, no η phase forms. The reason of which is that the added C reduces and/or restrains the resolving of the WC that locates at the interface, so that inhibit the W and C to form η phase with Fe and Co. The existence of large-size η phase near the interface is mainly attributed to the aggregation of small size η phase with the unsolved WC due to the stir of liquid metal, and then growing up.

The Effect of Cutting Surface Temperature on the Cutting Force of Aluminum Coated with Dilute Organic Polarity Substances.

Cutting force and surface roughness are decreased by a thin coating of dilute carboxylic acid whose number of carbon is more than 7. It is presumed that these phenomena are caused by the chemisorption of organic polarity substance molecules to Al atoms near by the dislocation. In this experiment, the coating materials are liquid paraffin containing 0.2mass% carboxylic acid (C 8H 16O 2, C 10H 20O 2 and C 14H28O 2) or various kinds of 0.2mass% organic polarity substances whose number of carbon is 18. Cutting surface temperature Tis controlled between 15 to 60°C by Peltier thermo module elements. Cutting speed and depth are 1.67mm/s and 0.05mm, respectively. The following results were obtained. 1) Cutting force (F T max and F N max) and surface roughness Ry are decreased by the coating of carboxylic acid at the cutting surface temperature under the acids melting point. 2) From the relation between ln(Frmax) and 1/T, activation energy is calculated at 120 to 200kJ/mol at the effective surface temperature for each acid. These values correspond to the formation energy of chemisorption between carboxylic acid molecules and Al atoms. 3)In the case of organic polarity substances except for carboxylic acid, these coating effects are not observed at the substances melting point.

The Effect of the Number of Carbon in Coated Carboxylic Acid on Orthogonal Cutting Force of Aluminum.

It is known that organic substances such as oleic acid (C188H34O2) coated on work-hardened metal surface affect the decrease of cutting force and surface roughness. According to our FTIR measurement, it is presumed that these coating effects are caused by the chemisorption of oleic acid molecules to metallic atoms near dislocation. In the present research, two groups of coating materials are examined, that is, 1) liquid paraffin or ethanol containing 0.2mass% organic substances of the number of carbon being 18 (C18H38, C18H36O2, C18H35O2Na and C18H38O), and 2) liquid paraffin containing 0.2 or 100mass% carboxylic acid (CxH2xO2, x:2-18). Cutting speed and depth are 1.67mm/s and 0.02mm, respectively. The following results were obtained. 1) Cutting force is decreased by coating of 0.2mass% carboxylic acid of x??7. 2) Surface roughness were drastically improved by the coating of organic substances which the number of carbon is more than 12. 3) Cutting force is always decreased by coating of 0.2mass% organic substances of x=18 with the polarity (C18H36O2, C18H35O2Na and C18H38O).

An investigation on corrosion potential of Al-Fe alloys in AlCl3 solution.

Effects of iron on the corrosion potential and behavior of Al-Fe alloys corroded in deaerated 0.1 M AlCl3 solution were studied by electrochemical measurements. Iron in Al-Fe alloys in the form of intermetallic compound dissolves into AlCl3 solution and deposits on the surface of aluminum in the solution. The cathodic reaction of hydrogen evolution easily occurs on the surface of the deposited iron. The aluminum matrix therfore remains a pitting corrosion state, where the corrosion potential is equivalent to the pitting corrosion potential -0.78 V vs. Ag/AgCl.

Cutting Texture of Fe-Si Alloy

The textures resulting from low speed cutting of Fe-3.14%Si alloy single crystals and polycrystalline specimens are examined by X-ray diffractometer. Some of results obtained are as follows.(1) Cutting the single crystals with various orientations, some preferred orientations were recognized in the deformed regions.(2) Cutting textures of polycrystalline specimens could be described as having {011} paral-lel to the cutting plane and parallel to the cutting direction. The dispersion of crystal orientation decreased with increasing grain size of those specimens. This {011} was characteristic component of textures in cutting surfaces, while it did not exsist in cold rolling textures of b. c. c. metals.(3) The main component {011} of the cutting textures of Fe-Si alloy was stronger in two pass cutting surface than one pass cutting surface.