Tetsuya Suganuma

Consolidation and mechanical properties of atomized Mg-based amorphous powders

Abstract The newly developed “clean process” enabled safe atomization and consolidation of fine Mg-based alloy powders. An Mg 85 Cu 5 Y 10 powder atomized at 923 K exhibited an amorphous phase in the particle size range smaller than 25 μm. A fully dense bulk amorphous Mg 85 Cu 5 Y 10 alloy in the cylindrical form 6 mm in diameter was obtained by extrusion at 373 K below T x . Amorphous Mg 87.5 Cu 5 Y 7.5 (smaller than 25 μm) extruded at 673 K above T x had a mixed structure consisting of Mg 24 Y 5 and Mg 2 Cu dispersed in an h.c.p. Mg matrix. The tensile strength for the bulk Mg 87.5 Cu 5 Y 7.5 alloy is 740 MPa at 298 K which is about twice as high as the highest value for conventional Mg alloys. The high strength is presumably due to the formation of the fine microstructure consisting of nanoscale intermetallic compound particulates homogeneously embedded in the Mg matrix with a fine grain size. The oxygen content of this alloy bulk produced by the “clean process” is 0.085 mass% which is half as low as the value for the bulk produced by the ordinary process in which the powders are exposed once in air. The tensile strength of the bulk extruded at an area reduction of 60% by the “clean process” is also about 43% as high as that for the bulk produced by the ordinary process. These data allow us to expect that the newly developed Mg-based alloys will proceed hereafter as a new type of high specific strength material.

Development of Sintered Integral Camshaft

The camshaft for an automobile engine is generally made of chilled cast iron. Due to increasing demand for higher performance, lower maintenance and better fuel economy, it is difficult to make the cast iron camshaft lighter and/or more durable. In order to overcome these problems, development of an integral camshaft comprised of a sintered alloy cam piece for better wear resistance and steel tube for weight saving has been accomplished. In 1981 Toyota Motor Corporation successively started the mass-production of the sintered integral camshaft for the new 1.8 liter 1s engine. The significant advantages are as follows; (1) Weight saving; (2) Excellent wear resistance; (3) Improvement of lubrication system; and (4) Saving machining cost.

DOUBLE-LAYER VALVE SEAT INSERTS FOR PASSENGER CAR DIESEL ENGINES

A new double-layer valve seat insert has been developed for use in high performance diesel engine of passenger car. The seat layer is composed of a sintered alloy of a high wear resistance and a high heat resistance. The base layer is composed of a sintered alloy of a higher heat resistance than that of the seat layer. This double-layer valve seat insert was proven to have good wear resistance and heat resistance in a durability test on the diesel engine with a turbocharger system.