KR20010053931A - High Strength Mn-Zn-Ca based alloys - Google Patents

Abstract

PURPOSE: An alloy is provided which has superior ordinary temperature strength and elongation by adding Ca to a Mg-Zn alloy. CONSTITUTION: The high strength Mg-Zn-Ca alloy comprises 5.0 to 6.5 wt.% of Zn, 0.1 to 0.5 wt.% of Ca and a balance of Mg. The tensile strength and elongation of the Mg-Zn-Ca alloy are much more increased compared to a Mg-6 wt.% Zn binary alloy due to grain micronization by addition of Ca according to the increase of an amount of Ca. On the contrary, the strength and elongation of the Mg-Zn-Ca alloy are decreased since a compound formed induces brittle fracture when the amount of Ca becomes 0.5 wt.% or more. Furthermore, the Mg-Zn-Ca alloy represents the similar to or more ordinary temperature tensile properties than an existing typical a Mg-Zn alloy of ZK61 and ZC63 alloys. The Mg-Zn-Ca alloy is suitable for a structural material of an automobile, airplane, etc. due to its light weight and can be used as a substitutional material for an existing Mg alloy structural material since the Mg-Zn-Ca alloy has the almost similar strength to an existing Mg-Zn-Zr alloy which represents the highest strength among the currently known Mg alloys and the Mg-Zn-Ca alloy is profitable in the aspects of production cost.

Description

High Strength Mn-Zn-Ca based alloys

The present invention relates to a high strength Mg-Zn-Ca-based alloy, and more particularly, to an alloy having excellent room temperature strength and elongation by adding Ca to the Mg-Zn-based alloy.

Currently, the goal of the development of new structural materials for transport equipment is to reduce fuel consumption and environmental problems due to light weight, and the use of the most suitable Mg alloy has recently increased rapidly.

Among them, ZK (Mg-Zn-Zr) system, which is a representative high strength Mg alloy, is known as the alloy system having the best room temperature strength among the alloys currently developed and commercialized due to the grain refinement effect due to the addition of zirconium.

As another Mg-Zn-based alloy, a ZE (Mg-Zn-RE) -based alloy having improved high temperature strength by adding a rare earth metal as a third element to refine grains has been developed and put into practical use.

In addition, a ZC (Mg-Zn-Cu) -based alloy in which Cu is added to the Mg-Zn alloy has also been developed.

However, the alloy added with double Zr increases the strength and elongation due to remarkable grain refinement, but there is a problem that the production cost increases due to the high melting point of Zr.

In addition, Mg-Zn-Re-based alloys and Mg-Zn-Cu-based alloys are relatively recently developed alloys, and are known to have excellent high temperature strength properties, but the room temperature strength characteristics are inferior to those of Mg-Zn-Zr alloys. There is a problem.

Accordingly, the present inventors have made efforts to develop Mg alloys having the same or higher strength and elongation at room temperature and Mg-Zn-Zr (ZK) -based and Mg-Zn-RE (ZE) -based alloys that have been developed and put into practical use. As a result of adding Ca as an alloy element that has not been developed, it has been found to have excellent room temperature strength and elongation, thereby completing the present invention.

An object of the present invention is to provide an Mg-Zn-Ca-based alloy having excellent room temperature strength and excellent elongation.

Mg-Zn-Ca alloy of the present invention for achieving the above object is characterized by consisting of 5.0 to 6.5% by weight of Zn, 0.1 to 0.5% by weight of Ca and the remaining Mg.

The present invention relates to an alloy formed by adding Ca to an Mg-Zn-based alloy, and the amount of Zn added is preferably 5,0 to 6.5% by weight.

Generally, Zn is added to improve strength by solid solution strengthening. If the amount is less than 5.0% by weight, there is a problem such as a decrease in strength due to the small amount of Zn content and a decrease in heat treatment effect. The problem of weakening of the material may occur.

On the other hand, Ca is an element that plays a role of increasing the strength and workability due to the refinement of the grains, and when the addition amount is less than 0.1% by weight, the effect of Ca addition is small, so there is a problem of strength decrease and weakness due to coarse grains, and 0.5 weight If it is more than%, there is a problem that the material exhibits a fragility that is destroyed even with a small impact by the production of Ca-containing compounds.

Referring to the method for producing an alloy of such a composition in detail as follows.

The alloy is prepared using pure Mg (purity 99.8%), Zn (purity 99.9%), and Mg-15 wt% Ca (purity of Ca 99.9%).

The alloy is melted in an argon gas atmosphere using an electric resistance furnace and cast in a gravity mold. At this time, Ar gas flows 0.4 L / min at the time of melting and 0.8 L / min at the time of casting, and the melting temperature is set at 740 ° C. and maintained at 720 ° C. for 1 hour before casting.

Hereinafter, the present invention will be described in detail with reference to the following Examples, but the present invention is not limited by the Examples.

In this embodiment,

The tensile test piece for the evaluation of tensile properties was made of a plate-shaped test piece having a parallel part length of 15.2 mm, a gage distance of 12.6 mm, a thickness of 2 mm, and a parallel part width of 5 mm. The error was set to 1/100.

Examples 1-4 and Comparative Examples 1-4

Next, the alloys were cast according to the same method as the composition ratio as shown in Tables 1 and 2, and mechanical properties were measured at room temperature in a kitchen state, and the results are shown in Table 1 below.

Alloy composition Tensile Strength (MPa) Yield strength (MPa) Elongation at Break (%) Example 1 Mg-6wt% Zn-0.1wt% Ca 225 72 9.3 Example 2 Mg-6wt% Zn-0.3wt% Ca 255 112 19.8 Example 3 Mg-6wt% Zn-0.5wt% Ca 159 71 7.6 Example 4 Mg-6wt% Zn-0.7wt% Ca 161 69 7.5 Comparative Example 1 Mg-6wt% Zn 214 92 8.9

On the other hand, the room temperature mechanical properties of the T6 heat-treated test piece was measured and shown in Table 2 below.

Alloy composition Tensile Strength (MPa) Yield strength (MPa) Elongation at Break (%) Example 1 Mg-6wt% Zn-0.1wt% Ca 283 180 7.5 Example 2 Mg-6wt% Zn-0.3wt% Ca 276 174 7.2 Example 3 Mg-6wt% Zn-0.5wt% Ca 191 111 5.1 Comparative Example 2 Mg-6wt% Zn-0.8wt% Zr 270 180 5 Comparative Example 3 Mg-6wt% Zn-3wt% Cu-0.5wt% Mn 240 145 5 Comparative Example 4 Mg-6wt% Zn-3wt% RE-0.7wt% Zr 300 190 10

As shown in Tables 1 and 2, it can be seen that the tensile strength and elongation are much increased compared to Mg-6wt.% Zn binary alloy by the grain refinement effect by Ca addition. However, when the amount of Ca is more than 0.5wt%, the resulting compound causes brittle fracture, so the strength and elongation were decreased. In addition, it can be seen that at room temperature tensile properties similar to or higher than the representative Mg-Zn-based alloys ZK61 (Comparative Example 1) and ZC63 alloy (Comparative Example 3) known to date.

As described in detail above, the Mg-Zn-Ca-based alloy of the present invention is lightweight and suitable as a structural material of transport equipment such as automobiles, aircrafts, etc., Mg-Zn-Zr-based alloys showing the highest strength among the currently known Mg alloys It is almost the same level and advantageous in terms of production cost, so it can be applied as a substitute for the existing Mg alloy structural material.

Claims (1)

A high-strength Mg-Zn-Ca-based alloy consisting of Zn 5.0 to 6.5 wt%, Ca 0.1 to 0.5 wt%, and the remaining Mg.