阅读说明：本技术 一种适合于铸造工艺的高导热铜合金及其制备方法 (High-thermal-conductivity copper alloy suitable for casting process and preparation method thereof ) 是由 李德江 胡波 黄彧 曾小勤 于 2021-06-22 设计创作，主要内容包括：本发明涉及一种适合于铸造工艺的高导热铜合金及其制备方法,该合金的成分为：2.0～3.5wt.％La,0～1.5wt.％Zn,0.001～0.5wt.％V,其余为Cu和不可避免的杂质。本发明通过限定La元素成分和控制铸造工艺来调控获得弥散分布的第二相组织,进而获得第二相强化的高导热铜合金。(The invention relates to a high heat conduction copper alloy suitable for casting process and a preparation method thereof, wherein the alloy comprises the following components: 2.0 to 3.5 wt.% La,0 to 1.5 wt.% Zn,0.001 to 0.5 wt.% V, and the balance Cu and unavoidable impurities. According to the invention, the second phase structure in dispersion distribution is obtained by limiting the La element components and controlling the casting process, so that the second phase strengthened high-thermal-conductivity copper alloy is obtained.)

1. A high-heat-conductivity copper alloy suitable for a casting process is characterized by comprising the following element components in percentage by mass: la 2.0-3.5%, Zn 0-1.5%, V0.001-0.5%, and the balance of copper and inevitable impurities.

2. The high thermal conductivity copper alloy suitable for casting process according to claim 1, wherein the contents of each element component by mass percentage are respectively: la 2.0-3.0%, Zn 0-1.5%, V0.001-0.5%, and the balance of Cu and unavoidable impurities.

3. The high thermal conductivity copper alloy suitable for casting process according to claim 1, wherein the contents of each element component by mass percentage are respectively: la 2.0-3.0%, Zn 0-1.0%, V0.001-0.5%, and the balance of Cu and unavoidable impurities.

4. The high thermal conductivity copper alloy suitable for casting process according to claim 1, wherein the contents of each element component by mass percentage are respectively: la 2.0-3.0%, Zn 0-1.0%, V0.01-0.1%, and the balance of Cu and unavoidable impurities.

5. The high thermal conductivity copper alloy suitable for casting process according to claim 1, wherein the contents of each element component by mass percentage are respectively: la 2.0%, Zn 0.5%, V0.05%, and the balance Cu and unavoidable impurities.

6. The method for preparing a high thermal conductive copper alloy suitable for a casting process according to any one of claims 1 to 5, comprising the steps of:

(1) weighing raw materials of pure copper, a Cu-La intermediate alloy, a Cu-Zn intermediate alloy and a Cu-V intermediate alloy according to the element component ratio;

(2) firstly, smelting pure copper, then preserving heat for the first time, then adding a Cu-La intermediate alloy and a Cu-V intermediate alloy, and preserving heat for the second time;

(3) cooling the melt obtained in the step (2), adding a Cu-Zn intermediate alloy for carrying out heat preservation for three times, and then adjusting the temperature and carrying out heat preservation for four times;

(4) and (4) finally, after the melt obtained in the step (3) is subjected to slag removal, pouring into a mold, and molding to obtain a target product.

7. The method for preparing a high thermal conductivity copper alloy suitable for a casting process according to claim 6, wherein the raw material is previously subjected to sand paper friction to remove oxide skin on the surface and expose a bright surface;

in the balance weight of each raw material, the burning loss of the La element is 10%, and the burning loss of the Zn element is 8%.

8. The method for preparing the high thermal conductivity copper alloy suitable for the casting process according to claim 6, wherein in the step (2), the temperature of the primary heat preservation is 1150 ℃ for 20 min;

the temperature of the secondary heat preservation is 1200 ℃, and the time is 30 min.

9. The method for preparing the high thermal conductivity copper alloy suitable for the casting process according to claim 6, wherein in the step (3), the temperature of the third heat preservation is 1100 ℃ and the time is 15 min;

the temperature for the fourth heat preservation is 1150 ℃ and the time is 30 min.

10. The method for preparing a high thermal conductivity copper alloy suitable for casting process according to claim 6, wherein in the step (4), after slag drawing, the copper alloy is poured into a mold with an initial temperature of 250 ℃ by metal mold gravity pouring at a melt temperature of 1150 ℃.

Technical Field

The invention belongs to the technical field of metal materials, and relates to a high-thermal-conductivity copper alloy suitable for a casting process and a preparation method thereof.

Background

The lead frame is an essential component of an integrated circuit, and is used for supporting a chip, communicating the chip with the outside and simultaneously dissipating heat of the chip when the circuit works. The scientific and technological development puts forward higher requirements on the running speed of electronic components, and then shells such as lead frames and the like are required to have higher heat-conducting performance. Copper and copper alloy have excellent heat conductivity and are the first choice as materials for lead frames. Pure copper has a high thermal conductivity of about 400W/(m.K), but its strength is too low to meet the requirements of lead frames for certain strength. To solve the problem of low strength of pure copper, most researchers achieve this in two ways: the first is to realize solid solution strengthening, second phase strengthening, fine grain strengthening and the like by adding a large amount of alloy elements; the second is to achieve solid solution strengthening, precipitation strengthening, work hardening, and the like by subsequent heat treatment or processing means such as solution aging, cold deformation, and the like. Although both methods can greatly improve the strength of the copper alloy, more heat-conducting property is lost. Moreover, the use of subsequent processes increases the time and economic costs in terms of materials. Therefore, it is urgently needed to develop a high thermal conductivity copper alloy with less addition of alloy elements, which is suitable for casting process without subsequent process treatment.

The alloying elements are present in copper alloys in mainly two forms: the first is the second phase. Under the condition of a certain element adding amount, in order to fully exert the strengthening effect of the second phase, the element for strengthening the second phase is selected to have a larger difference with the electronegativity of Cu so as to form the second phase with stronger binding force; in addition, from the aspect of the thermal conductivity of the copper alloy, alloy elements having a large difference from Cu in electronegativity, atomic size and the like should have a very small solid solubility in the Cu matrix so as to control the reduction of the thermal conductivity to the maximum extent. The low solid solubility copper alloy systems developed so far are Cu-Cr, Cu-Zr, etc., wherein the ultimate solid solubility of Cr in the Cu matrix is 0.7 wt.%, and the ultimate solid solubility of Zr in the Cu matrix is 0.11 wt.%. Although the two elements can strengthen the copper alloy and simultaneously greatly maintain the high heat-conducting property of the alloy, the alloy elements which are dissolved in the matrix still have great disadvantages on the heat-conducting property.

Currently, most copper alloys, while having sufficient strength, have greatly reduced thermal conductivity. Alloys such as Cu-Cr, Cu-Zr, Cu-Ni-Si, Cu-Ni-Zn and Cu-Ti are strong enough but remarkably deteriorated in heat conductivity. Most copper alloys have a thermal conductivity of less than 250W/(m.K), and it is difficult to satisfy the requirement of high thermal conductivity of the case material such as lead frame for high-speed electronic components. In addition, most high-thermal-conductivity copper alloys are prepared by subsequent heat treatment, cold deformation and other processes, so that the material cost is greatly increased. Therefore, how to improve the heat conductivity while maintaining the excellent characteristics of copper and copper alloys becomes a great obstacle to the development of copper alloys, and how to obtain a high heat conductivity copper alloy having a certain strength in an as-cast state becomes another great obstacle to the development of copper alloys.

Disclosure of Invention

The invention aims to provide a high-thermal-conductivity copper alloy suitable for a casting process and a preparation method thereof, so that the alloy has high thermal conductivity and/or strong mechanical properties.

The purpose of the invention can be realized by the following technical scheme:

one of the technical schemes of the invention provides a high-thermal-conductivity copper alloy suitable for a casting process, which is characterized by comprising the following element components in percentage by mass: la 2.0-3.5%, Zn 0-1.5%, V0.001-0.5%, and the balance of copper and inevitable impurities. Preferably, the Zn content is other than 0. When the Zn content is 0, it means that the copper alloy does not contain the Zn element.

Further, the mass percentage content of each element component is respectively as follows: la 2.0-3.0%, Zn 0-1.5%, V0.001-0.5%, and the balance of Cu and unavoidable impurities. Preferably, the Zn content is other than 0.

Further, the mass percentage content of each element component is respectively as follows: la 2.0-3.0%, Zn 0-1.0%, V0.001-0.5%, and the balance of Cu and unavoidable impurities. Preferably, the Zn content is other than 0.

Further, the mass percentage content of each element component is respectively as follows: la 2.0-3.0%, Zn 0-1.0%, V0.01-0.1%, and the balance of Cu and unavoidable impurities. Preferably, the Zn content is other than 0.

Further, the mass percentage content of each element component is respectively as follows: la 2.0%, Zn 0.5%, V0.05%, and the balance Cu and unavoidable impurities.

The second technical scheme of the invention provides a preparation method of a high-thermal-conductivity copper alloy suitable for a casting process, which comprises the following steps:

(1) weighing raw materials of pure copper, a Cu-La intermediate alloy, a Cu-Zn intermediate alloy and a Cu-V intermediate alloy according to the element component ratio;

(2) firstly, smelting pure copper, then preserving heat for the first time, then adding a Cu-La intermediate alloy and a Cu-V intermediate alloy, and preserving heat for the second time;

(3) cooling the melt obtained in the step (2), adding a Cu-Zn intermediate alloy for carrying out heat preservation for three times, and then adjusting the temperature and carrying out heat preservation for four times;

(4) and (4) finally, after the melt obtained in the step (3) is subjected to slag removal, pouring into a mold, and molding to obtain a target product.

Further, in the step (1), the raw material is rubbed with sandpaper in advance to remove oxide scales on the surface and expose a bright surface.

Further, in the step (1), the burning loss of the La element and the burning loss of the Zn element in the case of weighting the raw materials were 10% and 8%.

Further, in the step (2), the temperature of primary heat preservation is 1150 ℃ and the time is 20 min.

Further, in the step (2), the temperature of the secondary heat preservation is 1200 ℃, and the time is 30 min.

Further, in the step (3), the temperature for the third heat preservation is 1100 ℃, and the time is 15 min;

further, in the step (3), the temperature for four times of heat preservation is 1150 ℃ and the time is 30 min.

Further, in the step (4), after slag is pulled out, the slag is poured into a mold with the initial temperature of 250 ℃ by adopting a metal mold gravity pouring mode at the temperature of 1150 ℃.

The invention solves the problems of heat conductivity and the like by doping the rare earth elements. The electronegativity of the rare earth elements is mostly between 1.10 and 1.30, is lower than that of Cr (1.66) and Zr (1.33), has a larger difference with that of Cu (1.90), and most of the rare earth elements can form a second phase with strong binding force. In addition, most rare earth elements have extremely low solid solubility in the Cu matrix, even have no solid solubility, and can realize second phase strengthening while maximally maintaining the high heat conductivity of the copper alloy.

Another form of presence of alloying elements in copper alloys is: solid solution atoms. Although the presence of solid solution atoms has a large influence on the thermal conductivity, it is necessary to appropriately strengthen the Cu matrix. Generally, the closer the number of nuclear charges, atomic size, electronegativity, extra-nuclear electron arrangement, and the like of the solid solution atoms and the copper atoms are, the smaller the influence of the solid solution atoms on the heat conductivity of the copper alloy is. Therefore, when solid solution strengthening atoms are selected, alloy elements having properties close to those of copper atoms in each aspect, a large amount of solid solution in the Cu matrix, and no additional second phase are selected as much as possible.

According to the theory of thermal conductivity, the thermal conductivity of an alloy can be expressed as:

wherein kappa is the thermal conductivity coefficient of the alloy, C is the specific heat capacity of the alloy, v is the movement speed of the heat-conducting particle carrier, and l is the mean free path of the particles. In the alloy, the addition of a small amount of alloy elements has little influence on the specific heat capacity and the particle movement speed, but greatly influences the mean free path of the particles. Solid solution atoms with larger difference from the thermal property of copper atoms greatly change the Brillouin zone of copper and cause lattice distortion, thereby reducing the mean free path of particles; the second phase of the network will also greatly hinder the movement of the carrier of the heat-conducting particles, thereby reducing the mean free path of the particles. Therefore, in order to obtain a copper alloy material having high thermal conductivity, it is necessary that the second phase in the structure is dispersed and the solid solution atoms are close to the thermal physical properties of the copper atoms.

In the invention, rare earth element La and matrix element Cu react to generate Cu which is stable at high temperature and is dispersed and distributed₆The La second phase can effectively strengthen the copper alloy. The solid solubility of La in the Cu matrix is 0, so that lattice distortion and other adverse effects on the matrix cannot be caused; in addition, Cu is dispersed₆The La second phase has less obstruction to movement relative to the thermally conductive particle carrier. Therefore, the rare earth element La effectively strengthens the copper alloy while minimizing the reduction of the thermal conductivity.

The properties of the alloy element Zn and the matrix element Cu are similar, wherein the nuclear charge number is only different by 1, the atomic weight is only different by 2.9%, the atomic volume is only different by 28.1%, the nuclear external electron arrangement is similar, and the electronegativity is only different by 0.25. Therefore, the introduction of the Zn element has the minimum change to the Brillouin zone of the Cu and the minimum distortion to the lattice, so that the ultimate solid solubility of the Zn in the Cu matrix is as high as 39 percent, and the Zn is an effective element for solid solution strengthening of the Cu matrix and simultaneously keeping the high heat conductivity of the copper alloy.

The alloy element V is not dissolved in the Cu matrix and does not react with the Cu element, is precipitated in the copper alloy firstly, and is an effective element for strengthening the Cu matrix by fine grains.

Compared with the prior art, the invention has the following advantages:

(1) the invention analyzes the influence of different alloy elements on the heat conductivity of the copper alloy based on a heat conduction theory, and provides a method for obtaining a microstructure with a second phase in a dispersed distribution and small lattice distortion by selecting alloy components and regulating and controlling a casting process in the design process of the high heat conductivity copper alloy. The high-thermal-conductivity copper alloy is designed from the viewpoints of strengthening the copper alloy by the second phase and the solid solution atoms and influencing the mean free path of the heat-conducting particle carriers, and has certain strength and excellent heat-conducting property.

(2) The 90HV hardness value of the Cu-2La-0.5Zn-0.05V alloy in the high-heat-conductivity copper alloy is greatly improved compared with 45HV of pure copper, and the high-heat-conductivity coefficient of 285W/(m.K) is still obtained.

(3) The preparation method of the high-thermal-conductivity copper alloy is very simple, can be completed by a conventional casting method, does not need subsequent complex processes such as cold deformation and heat treatment, and greatly reduces the time cost and the economic cost of material preparation.

(4) The high-thermal-conductivity copper alloy meets the requirements of shells such as lead frames on certain strength and high thermal conductivity, can conduct heat generated by operation of electronic devices more efficiently, and greatly prolongs the service life of electronic components.

Drawings

FIG. 1 is a schematic view of the thermal conductivity of a Cu-La-Zn-V based high thermal conductivity copper alloy with different La contents;

FIG. 2 is a schematic view showing the thermal conductivity of a Cu-La-Zn-V based high thermal conductivity copper alloy with different Zn contents;

FIG. 3 is a schematic diagram of XRD phase analysis of a high thermal conductivity copper alloy Cu-2La-0.5 Zn-0.05V;

FIG. 4 is a schematic drawing showing the as-cast microstructures of Cu-2La-0.5Zn-0.05V and Cu-4La-0.5Zn-0.05V alloys.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments. The present embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation manner and a specific operation process are given, but the scope of the present invention is not limited to the following embodiments.

In the following examples, unless otherwise specified, all the conventional commercially available raw materials or conventional processing techniques in the art are indicated.

Example 1

For example, 3kg of Cu-2La-0.5Zn-0.05V (i.e., the copper alloy has a composition of 2.0 wt.% La, 0.5 wt.% Zn, 0.05 wt.% V, and the balance Cu and unavoidable impurities) was used to prepare a cast copper alloy. The method comprises the following specific steps:

selecting pure copper, Cu-La, Cu-Zn and Cu-V intermediate alloys as metallurgical raw materials, and removing oxide skins on the surfaces of the raw materials by using 320# SiC abrasive paper to expose bright surfaces for later use;

step two, the raw materials processed in the step one are proportioned and weighed according to the mass percentage of the specific alloy, wherein the burning loss of the La element is 10 percent and the burning loss of the Zn element is 8 percent;

step three, putting the pure copper weighed in the step two into an induction furnace for smelting, and preserving heat for 20min at 1150 ℃;

step four, adding the Cu-La and Cu-V intermediate alloy weighed in the step two into the melt after heat preservation for 20min, and preserving the heat for 30min at 1200 ℃;

step five, cooling the melt subjected to heat preservation in the step four to 1100 ℃, adding the weighed Cu-Zn intermediate alloy in the step two, and preserving heat for 15 min;

step six, preserving the heat of the melt processed in the step five for 30min at 1150 ℃, and orderly stirring the melt clockwise from top to bottom every 10min so that the added intermediate alloy is completely melted and all alloy elements are uniformly distributed in the melt;

and step seven, rapidly pulling out slag from the melt processed in the step six, and pouring the melt into a metal mold die with the temperature of 250 ℃ by adopting a metal mold gravity pouring mode under the condition that the temperature of the melt is 1150 ℃.

The cast Cu-2La-0.5Zn-0.05V copper alloy obtained in this example was analyzed by XRD and the structure thereof was found to have only a-Cu matrix and Cu as shown in FIGS. 3 and 4 (a)₆A second phase of La, and Cu₆The second phase of La is in a dispersed distribution. The heat conductivity and hardness values of the copper alloy are measured, and the addition of the alloy elements increases the hardness of pure copper from 45HV to 90HV, and the heat conductivity of the cast Cu-2La-0.5Zn-0.05V copper alloy is as high as 285W/(m.K).

Example 2

For example, 3kg of Cu-2La-1.0Zn-0.05V (i.e., the copper alloy has a composition of 2.0 wt.% La, 1.0 wt.% Zn, 0.05 wt.% V, and the balance Cu and unavoidable impurities) was used to prepare a cast copper alloy. The specific procedure was the same as in example 1.

The cast copper alloy obtained in this example still had only a-Cu matrix and Cu in the structure₆A second phase of La, and Cu₆The second phase of La is in a dispersed distribution. Compared with the Cu-2La-0.5Zn-0.05V alloy in the embodiment 1, the Cu-2La-1.0Zn-0.05V prepared by the embodiment has the thermal conductivity coefficient reduced to 265W/(m.K) but still higher than 250W/(m.K), and can well meet the requirement of housings such as lead frames on high thermal conductivity of materials.

Example 3

For example, 3kg of Cu-2La-0.5Zn-0.001V (i.e., the copper alloy has a composition of 2.0 wt.% La, 0.5 wt.% Zn,0.001 wt.% V, and the balance Cu and unavoidable impurities) is used to prepare a cast copper alloy. The specific procedure was the same as in example 1.

The cast copper alloy obtained in this example had a structure with a phase composition similar to that of example 1, but with relatively coarse grains. Compared with the Cu-2La-0.5Zn-0.05V alloy in the example 1, the Cu-2La-0.5Zn-0.001V prepared by the example has the thermal conductivity coefficient improved to 295W/(m.K) but the hardness reduced to 85 HV.

Example 4

For example, 3kg of Cu-2La-0.5Zn-0.5V (i.e., the copper alloy has a composition of 2.0 wt.% La, 0.5 wt.% Zn, 0.5 wt.% V, and the balance Cu and unavoidable impurities) was used to prepare a cast copper alloy. The specific procedure was the same as in example 1.

The cast copper alloy obtained in this example had a phase composition in the structure identical to that of example 1, but the crystal grains were relatively fine. Compared with the Cu-2La-0.5Zn-0.05V alloy in the example 1, the Cu-2La-0.5Zn-0.5V alloy prepared by the example has the thermal conductivity reduced to 274W/(m.K), but the hardness increased to 97 HV.

Example 5

For example, 3kg, a cast copper alloy is prepared according to a Cu-2La-0.5Zn-0.01V ratio (i.e., the copper alloy has a composition of 2.0 wt.% La, 0.5 wt.% Zn, 0.01 wt.% V, and the balance Cu and unavoidable impurities). The specific procedure was the same as in example 1.

The cast copper alloy obtained in this example had a structure with a phase composition similar to that of example 1, but with relatively coarse grains. Compared with the Cu-2La-0.5Zn-0.05V alloy in the embodiment 1, the Cu-2La-0.5Zn-0.01V alloy prepared by the embodiment has the thermal conductivity coefficient improved to 290W/(m.K), but the hardness is reduced to 86 HV.

Example 6

For example, 3kg of Cu-2La-0.5Zn-0.1V (i.e., the copper alloy has a composition of 2.0 wt.% La, 0.5 wt.% Zn, 0.1 wt.% V, and the balance Cu and unavoidable impurities) was used to prepare a cast copper alloy. The specific procedure was the same as in example 1.

The cast copper alloy obtained in this example had a phase composition in the structure identical to that of example 1, but the crystal grains were relatively fine. Compared with the Cu-2La-0.5Zn-0.05V alloy in example 1, the Cu-2La-0.5Zn-0.1V alloy prepared in the example has a thermal conductivity reduced to 283W/(mK), but the hardness increased to 93 HV.

Comparative example 1

For example, 3kg, a cast copper alloy is prepared according to a Cu-4La-0.5Zn-0.05V ratio (i.e., the copper alloy has a composition of 4.0 wt.% La, 0.5 wt.% Zn, 0.05 wt.% V, and the balance Cu and unavoidable impurities). The specific procedure was the same as in example 1.

The hardness of the cast Cu-4La-0.5Zn-0.05V copper alloy prepared in the embodiment is raised to 112HV due to the obvious second phase strengthening. Unfortunately, however, as shown in the b diagram of FIG. 4, only the α -Cu matrix and Cu are present in the structure₆La second phase, but Cu₆The La second phase is distributed in a network shape at a crystal boundary, so that the mean free path of the heat-conducting particle carrier is greatly reduced, and the influence on the heat-conducting property of the alloy is large. As shown in FIG. 1, the thermal conductivity of the cast copper alloy is 215W/(mK) and is lower than 250W/(mK). Therefore, the mass percentage of the alloy element La should not be too high, which would result in a great loss in the heat conductivity of the alloy. As can also be seen from fig. 1, within a certain range, the increase in the mass percentage of La element results in the loss of the thermal conductivity of the alloy.

Comparative example 2

For example, 3kg, a cast copper alloy was prepared according to the Cu-2La-2Zn-0.05V ratio (i.e., the copper alloy had a composition of 2.0 wt.% La, 2.0 wt.% Zn, 0.05 wt.% V, and the balance Cu and unavoidable impurities). The specific procedure was the same as in example 1.

As shown in FIG. 2, the excessive addition of Zn element greatly increases lattice distortion in the Cu matrix and reduces the mean free path of the heat-conducting particle carrier, so that the heat conductivity coefficient of the copper alloy is reduced to 227W/(m.K) and is lower than the requirement of 250W/(m.K). Therefore, the mass percentage of the alloy element Zn is not high enough, otherwise the heat conductivity of the alloy is rapidly reduced.

Comparative example 3

For example, 3kg, a cast copper alloy is prepared according to a Cu-0.5Zn-0.05V ratio (i.e., the copper alloy has a composition of 0.5 wt.% Zn, 0.05 wt.% V, and the balance Cu and unavoidable impurities). The specific procedure was the same as in example 1.

The cast Cu-0.5Zn-0.05V copper alloy prepared in this example could not form a second phase and further strengthen the alloy due to the absence of La element, and compared with the Cu-2La-0.5Zn-0.05V alloy in example 1, the hardness of the Cu-0.5Zn-0.05V alloy prepared in this example was only 62HV, and could not satisfy the requirements of the structural members such as lead frame and the like for mechanical properties.

Comparative example 4

For example, 3kg of a cast copper alloy was prepared according to a Cu-2La-0.05V ratio (i.e., the copper alloy had a composition of 2.0 wt.% La, 0.05 wt.% V, and the balance Cu and unavoidable impurities). The specific procedure was the same as in example 1.

The cast Cu-2La-0.05V copper alloy prepared in this example failed to perform solid solution strengthening of the copper matrix due to the absence of Zn element, and the hardness of the Cu-2La-0.05V alloy prepared in this example was reduced to 85HV compared to the Cu-2La-0.5Zn-0.05V alloy in example 1.

Comparative example 5

For example, 3kg of a cast copper alloy was prepared according to the Cu-2La-0.5Zn ratio (i.e., the composition of the copper alloy: 2.0 wt.% La, 0.5 wt.% Zn, and the balance Cu and unavoidable impurities). The specific procedure was the same as in example 1.

The cast Cu-2La-0.5Zn copper alloy of this example failed to refine the crystal grains due to the absence of V element, and the hardness of the Cu-2La-0.5Zn alloy of this example was reduced to 84HV compared to the Cu-2La-0.5Zn-0.05V alloy of example 1.

The embodiments described above are described to facilitate an understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.