Abstract

Research has been conducted on a high-strength, heat-resistant extruded and forged magnesium alloy able to be formed into large-diameter ingots, with a view towards application in pistons for internal combustion engines, parts in which weight savings are sought. The addition of Zr to an Mg96Zn2Y2 (at.%) alloy with a long-period stacking ordered structure phase refined the crystal grains. In addition, the use of a new casting method in which the ingot case is rotated and the molten metal is agitated helped to prevent segregation and the coarsening of the crystal grains, in order to make it possible to form large ingots (diameter: 335 mm; height: 850 mm) for extrusion displaying fine and uniform microstructures. Following formation of extruded pieces of 100 mm in diameter at an extrusion ratio of 10, dummy piston shapes were forged, and the mechanical properties of the material were measured before and after forging. From room temperature to 573 K, the developed alloy displayed tensile and fatigue strength in excess of commercial aluminum alloys. The alloy displayed a 0.2% yield strength of 209 MPa at 523 K following forging, approximately twice that of the high-strength aluminum alloy A4032-T6 that is used as a piston material. The addition of a high specific gravity element had minimal effect on the alloy’s density, and reduced its weight to approximately 70% that of aluminum alloys. Given the above, the developed Mg-Zn-Y forged alloy can be considered to be an extremely promising material in terms of realizing fuel efficiency and performance increases through the achievement of weight reductions in automobile, motorcycle and power product pistons.

References

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Author (organization or company)

• Yuichi IENAGA（Power Products R&D Center）

Publication Information

Article of Honda R&D Technical Review Vol.28 No.1 (183 - 190)

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