Process for Production of a Carboxylic Acid/Diol Mixture Suitable for Use in Polyester Production

Abstract

Disclosed is a wrought magnesium alloy having excellent strength and extrusion or rolling formability, and a method of producing the same. The wrought magnesium alloy comprises 0.1-1.5 at % group IIIa, 1.0-4.0 at % group IIIb, 0.35 at % or less of one selected from the group consisting of groups IIa, IVa, VIIa, IVb, and a mixture thereof, 1.0 at % or less of group IIb, and a balance of Mg and unavoidable impurities and thus has a second phase composite microstructure. The wrought magnesium alloy of the present invention has high strength, toughness, and formability in addition to the electromagnetic wave shield ability of magnesium. Accordingly, the wrought magnesium alloy is a material useful to portable electronic goods, such as notebook personal computers, mobile phones, digital cameras, camcorders, CD players, PDA, or MP3 players, automotive parts, such as engine room hoods, oil pans, or inner panel of door, or structural parts for airplane.

Description

TECHNICAL FIELD[0001]The present invention relates to a wrought magnesium alloy, which contains a second phase consisting of an intermetallic compound, thereby having excellent strength, formability, and corrosion resistance. More particularly, the present invention pertains to a wrought magnesium alloy, which comprises 0.1-1.5 at % group IIIa. 1.0-4.0 at % group IIIb, 0.35 at % or less of one selected from the group consisting of groups IIa, IVa, VIIa, IVb, and a mixture thereof, 1.0 at % or less group IIb, and a balance of Mg and unavoidable impurities and which thus has a second phase composite microstructure consisting of an intermetallic compound, and a method of producing the same.BACKGROUND ART[0002]Having a density of 1.74-1.95 g / cm3 or so, a relatively low specific gravity that is ⅔ of that of aluminum, excellent specific strength and machinability, magnesium alloys have been developed as light structural materials for airplanes and automobiles. However, since magnesium has...

AI Technical Summary

Benefits of technology

[0007]Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a wrought magnesium alloy which contains the intermetallic compound coherent to a matrix microstructure and which has a second phase composite microstructure, thereby improving elongation and anisotropy to assure excellent formability and corrosion resistance. In order to accomplish the above object, an alloy consisting of three or more elements is used to activate a slip plane. Additionally, in order to activate the slip plane according to increasing in temperature, IIIa and IIIb groups are added together to reduce stacking fault energy and to improve corrosion resistance of the matrix microstructure. Furthermore, fine intermetallic compound particles dispersed during extrusion and rolling processes are employed to improve strain hardening ability and formability.Technical Solution

[0008]In order to accomplish the above object, the present invention provides a wrought magnesium alloy having excellent formability and plating properties, which comprises 0.1-1.5 at % group IIIa, 1.0-4.0 at % group IIIb, 0.35 at % or less of one selected from the group consisting of groups IIa, IVa, VIIa, IVb, and a mixture thereof, 1.0 at % or less of group IIb, and a balance of Mg and impurities and which thus has a second phase intermetallic compound.

Problems solved by technology

However, since magnesium has a hexagonal close packed (HCP) lattice crystal structure, formability is very low, and thus, the application is limited to a field in which the forming is achieved using a casting process.

Particularly, its practical use is limited due to problems, such as severe oxidation of melts, reduction of strength at high temperatures, and low corrosion resistance.

On the other hand, it is disadvantageous in that since micropores are formed as a casting process due to the addition of Zn, it is difficult to apply the Mg—Zn alloy to a casting process, such as die-casting.

Additionally, it is difficult to desirably improve strength because it is grown as the coarse grain.

However, even though their microstructures have a single-phase solid solution and thus have excellent ductility, they are disadvantageous in that since a strain hardening ability is poor and it is difficult to prevent the grain growth, formability is poor due to anisotropy.

However, the technology is problematic in that the different heating temperatures of the different portions significantly increase the production cost of a press mold.

However, this method is disadvantageous in that the powder is expensive, and in that it is difficult to apply an electroplating process because the powder pressed material has a porous structure.

Magnesium has low corrosion resistance, and thus, it is necessary to treat a surface of magnesium, but undesirably, a gas phase plating process or an electroless plating process requires chemical and treatment costs that are much higher than the electroplating process.

However, products having high porosity and low density, such as die-casting and thixo-molding products, are difficult to apply to a wetplating process because corrosion occurs due to chemicals soaked into the pores.

However, even though the alloy containing Zn in an amount of 2% or more has high strength, it has a disadvantage in that free zinc (Zn) readily forms a low melting point eutectic phase.

And the plate is easily cracked at both sides during a rough rolling process for breaking the coarse dendrite structure, so draw-ability is poor because of high anisotropy.

Laid-Open Publication No. 2002-0078936 (U.S. Pat. No. 6,471,797) discloses a method of improving strength and formability using a Mg—Zn—Y eutectic ternary alloy quasi-crystalline phase which contains 1-10 at % Zn and 0.1-3 at % Y. However, this method is disadvantageous in that the amount of Zn must be enough so as to desirably assure a quasi-crystalline phase effect.

The composition of a cast product is not uniform because a specific gravity between zinc and magnesium is significantly different.

The micro-pores at the grain boundary reduce corrosion resistance, and tears form at sides of a plate during the hot rolling process.

Accordingly, it is difficult to uniformly disperse them.

However, the eutectic phase mostly has a coarse microstructure that is incoherent to a matrix microstructure, and thus, formability is insufficiently improved.

However, these patents are useful to cast products, but cannot be directly applied to wrought products.

However, the patent cannot be applied to wrought products because the product cost significantly increases due to the use of a lot expensive elements, and the coarse intermetallic compounds are incoherent to the matrix.

However, this method is not useful to casing materials when considering a Galvanic reaction of Li and an increased cost due to the use of an excessive amount of Li.

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