Teruhisa Watanabe

Formation Process of Intermetallic Compounds in Aluminum-Iron P/M Alloys Made by Mecanical Alloying

We have recognized that A1-8wt%Fe P/M alloys made by mechanical alloying(MA) for 54ks had tensile Strength of 365MPa at 298K, 258Mpa at 523k. And Main reason is that very small Al-Fe intermetallic compound partickles are dispersed uniformally in the Alminum matrix, Therefore, we tried to clear on the formation process of Al-Fe intermetallic compounds in A1-8wt%Fe P/M alloys made by MA.According to the XRD patterns of the dispersoids, the specimens of MA and non-annealed powder, MA and 673K annealed powder and MA, 673K annealed and 773K extruded alloy were deeply corroded by phenol at 433K in order to pick out from the aluminum matrix, the MA, non-annealed powder showed only Fe peaks, the MA, annealed powder showed some peaks like Al-Fe intermetallic compounds, and the MA, annealed and extruded alloy showed clearly A13Fe peaks.On the other hand, according to DTA results of MA and non-annealed powder, two exothermic reactions were obserbed, the one appeared at about 5739, another appeared at about 673K.From the results of shoves, on the production process of A1-8wt%Fe P/M alloys made by MA, only Fe particles were dispersed in the Aluminum matrix before heating treatments, and the time when the Fe particles began to change Al-Fe intermetallic compounds were in the heating treatment processes.

Properties of High Strength P/M Aluminum Alloy Sheets Rolled from Sintered Compacts of Alloyed and Mixed Powders

P/M 7091 alloy sheets were rolled directly from sintered compacts, and the properties of the sheets were investigated. The alloy powder, and the mixed powders M1 and M2 having same composition of 7091 alloy were used for starting powders. M1 was the mixture of AI-Zn-Co mother alloy, Al-Mg mother alloy, Al-Cu mother alloy and Al elemental powders. M2 was the mixture of Al-Co mother alloy, Zn, Mg and Cu elemental powders. The green compacts of the alloy powder and the M1, M2 powders were sintered 803-863 K for 1 h in N2. The sintered compacts were hot rolled and cold rolled, then were heat treated to T6 condition. Results obtained were as follows:1) While the cracking of P/M sheets often occurred during hot rolling process when they were made from 7091 alloy powder and mixed powder M1. The cracking of the sheet from mixed powder M2 was not observed.2) The highest UTS and elongation values of the P/M sheets rolled from sintered compacts in this study were about 590MPa and 11%, but these values were lower than those of the P/M sheets rolled from degassed and hot pressed compacts of 7091 alloy powder.3) Hydrogen contents of the P/M sheets rolled from sintered compacts decreased with increasing the sintering temperature. And it was less than 2 p.p.m., for the sheets rolled from compacts sintered at 863 K.

Influences of alloy elements in infiltrant on mechanical properties of copper-alloy infiltrated P/M high speed steels

Elements in Infiltrant on Mechanical Properties of Copper-alloy Infiltrated P/M High Speed SteelsMechanical properties of copper-alloy infiltrated M42, T42 P/M high speed steels were studied.The green compacts were sintered in vacuum at 1433, 1443, 1453 K to make skeletons. The skeletons were infiltrated with Cu-Cr, Cu-Co and Cu-Fe-Mn alloy infiltrants in hydrogen or argon at 1423 K for 1.8 ks.The result obtained were summarized as follows.1)All the infiltrated specimens shrinked.The Cu-Fe-Mn infiltrated M42, T42 P/M high speed steels had the least amount of dimentional change values during infiltration.The Cu-Fe-Mn infiltrated M42, T42 P/M steels had comparatively high hardness, but low strength.2)Cu-Cr, Cu-Co infiltrated P/M high speed steels showed high strength, especially the P/M M42 steel having a skeleton sintered at 1453 k in vacuum and infiltrated with the Cu-Co alloy infiltrant in hydrogen had 2450 MPa of transverse rupture strength and HRC 48 of hardness as infiltrated.

Effects of Permeability of Sintered Bronze Bearings on the Sliding Noise

Sintered bronze bearing specimens having various permeabilities within the range of 0.6-60 × 10-3 darcys were prepared for measurements of the sliding noise using a resting apparatus which was designed by us. The specimens were made from atomized bronze alloy powders having three kinds of particle size of 200/250, 250/350, 350/400 mesh by controlling the intercommunicating porosity of bearing specimens in 6, 9, 12, 15, 18 and 21 vol% during compacting, sintering and sizing processes.The results obtained were as follows;With the decrease of permeability from about 60 × 10-3 darcys, the sliding noise also decreased gradually and came to a minimum level at a certain value of permeability, which was about 2 × 10-3 darcys in this study. However, when the specimens having smaller values of permeability than the certain value were driven. the sliding noise rather showed a tendency of increase with decreasing permeability.And on causalities in the above results, they were able to be explained by considering the effects of permeability upon the mechanism of self-lubrication of Sintered porous bearings.

Sintered Manganese Steel. (Part III)

Effects of repressing and resintering on the physical and mechanical properties of sintered compacts were studied.The results obtained were as follows :(1) Microstructures of sintered compacts have a large effect on the repressing ratio and the increase in density. Ferritic and austenitic structures give large repressing ratios.(2) On repressing sintered compacts containing Mn 10% and C 1.2% which might show martensitic structure, pre-sintering at a lower temperature and pre-pressing at a lower compacting pressure are recommended, while, for the compacts containing Mn 20% and C 2.0% which might show austenitic structure, pre-sintering at a higher temperature and prepressing at a higher compacting pressure are recommended.(3) On cyclic sintering and pressing, tensile strength and elongation of sintered compacts of ferritic and austenitic structures are saturated by a single process of repressing and resintering, but those of martensitic structure are not saturated even by repressing and resintering three times. Repressing is less effective for martensitic structures than for ferritic or austenitic structures.(4) Mechanical properties of sintered manganese steel are much affected by repressing and resintering treatments. Tensile strength of about 35-40kg/mm2, elongation of about 8-13%, and impact energy of about 2-6kg-m/cm2 can be obtained for austenitic manganese steel.