High strength and high toughness alloy with low density and the method of making

Abstract

The present invention relates to a high strength and high toughness alloy with a low density and the method of making thereof. The alloy essentially comprises 15 to 33 wt % of manganese, 6 to 10 wt % of aluminum, 0.6 to 1.2 wt % of carbon, 0.1 to 1.0 wt % of silicon, and the balance of iron. The alloy has excellent properties of a density of 6.6 to 6.9 g / cm3, an elongation of 25 to 70%, and a tensile strength of 100 to 190 ksi. In particularly, and the alloy is useful for golf club heads with excellent properties. Further, the use of the alloy reduces pits and defects generated during the electroplating process of the heads. Therefore, the defect rate of the product is remarkably decreased so that the cost is reduced.

Description

FIELD OF THE INVENTION[0001]The present invention relates to a high strength and high toughness alloy with a low density and the method of making thereof. Due to its characteristics of low density, excellent elongation, high strength and high damping capacity, the alloy is particularly useful for manufacturing golf club heads with large volume, high strength and high toughness to achieve better performance of playing golf. Furthermore, the use of the alloy can efficiently prevent the pits and defects generated during the electroplating process of the heads. Accordingly, the defect rate of the product can be significantly lowered so that the cost is remarkably reduced.DESCRIPTION OF THE RELATED PRIOR ART[0002]The characteristics of alloy, such as density, melting point, strength, ductility, thermal conductivity, resistances to corrosion and oxidation, etc., are varied depending on alloying elements. With different requirements for various applications and designs of various mechanica...

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Benefits of technology

[0020]Depending on the theory of the alloy design and the study of the microstructures in the Fe—Al—Mn—C alloys by means of the transmission electron microscopy(TEM), the present inventors has developed a low-density Fe—Al—Mn—C alloy with high strength and ductility and the method of making. The alloy has a density of 6.6 to 6.9 g / cm3, an elongation of 25 to 70%, and a tensile strength of 100 to 190 ksi. In particular, the use of the alloy on manufacturing golf club heads is capable of reducing the pits and defects generated during the electroplating process of the heads, so that the yield rate of the products is remarkably increased.

[0026]4. Si: Addition of 0.1 wt % or more of silicon enhances (Fe,Mn)3AlCx carbides to finely and coherently form in the austenite phase through spinodal decomposition during quenching so that the strength of alloy is raised. Also, addition of Si increases fluidity of liquid alloy and facilitates casting of alloy. However, Si is not only a strong ferrite former but also an element to enhance the formation of the brittle D03 ordered in Fe—Mn—Al alloys. When the Si content is more than 1.0 wt %, brittle D03 ordered phase is formed, and the ductility of alloy is seriously deteriorated. Therefore, the Si content should be controlled to be equal to or greater than 0.1 wt. % but lower than or equal to 1.0 wt %.

[0027]5. Mo: The present inventors found that the addition of molybdenum to the Fe—Mn—Al alloys can increase the strength by the mechanism of the solid-solution strengthening. However, when the Mo content is more than 1.5 wt %, molybdenum carbides like M2C, M23C6 and M6C are observed to precipitate in the alloy. The presence of the molybdenum carbides leads to the lack of carbon in the vicinity of the carbides, and makes the austenite phase unstable and then tends to transform into the less-ductility ferrite phase. Therefore, the Mo content should be controlled to be not more than 1.5 wt %.

[0028]To achieve the above objects, the present inventors has focused on ratio and composition of various added elements and develop a high strength and high toughness alloy with low density, which comprises 15 to 33 wt % of manganese, 6 to 10 wt % of aluminum, 0.6 to 1.2 wt % of carbon, 0.1 to 1.0 wt % of silicon, with up to 1.5 wt % of molybdenum, and the balance of iron.

Problems solved by technology

However, when more than 10 wt % Al is added, ferrite phase is formed and disordered ferrite phase (bcc) tends to transform into brittle D03 ordered phase during heat treatments.

This does not elevate the strength of the alloy and, on the contrary, sharply reduces ductility of alloy.

Similarly, the amount of (Fe,Mn)3AlCx carbides formed in austenite phase is too low when the added amount of C is less than 0.6 wt %, and desired strength of alloy can not be obtained.

However, when more than 1.2 wt % C is added, the carbides are observed to have large sizes and start to precipitate at grain boundaries.

This makes the alloy susceptible to intergranular fracture and ductility is sharply reduced.

When the Si content is more than 1.0 wt %, brittle D03 ordered phase is formed, and the ductility of alloy is seriously deteriorated.

The presence of the molybdenum carbides leads to the lack of carbon in the vicinity of the carbides, and makes the austenite phase unstable and then tends to transform into the less-ductility ferrite phase.

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