1. Rare earth copper and copper alloys have a series of special properties, such as excellent electrical and thermal conductivity, good corrosion resistance, non-magnetic properties, corrosion resistance to microorganisms and algae in water, easy plastic processing and good solderability, etc. , it has become an important material in modern industry and has been widely used in electronics, mechatronics, aviation, aerospace and other sectors. Rare Earth elements have typically metallic properties, such as their highly reactive chemical property, which interact with almost all elements other than noble gases, making them the “Monosodium glutamate”of metallurgy. The application of rare earth elements in copper and copper alloys has attracted the attention of scientists and technologists in the 1950s, and has become a research hotspot. As early as the 1960s, the research on the application of rare earth in copper and copper alloys began in China. At that time, the research mainly focused on improving the cold and hot working properties, corrosion resistance and wear resistance of copper and copper alloys, and achieved some useful results, but these research has been slow progress, development and application of the field is not much. 2. Effect of rare earth on microstructure of copper and copper alloy 01 there are two main ways to purify microstructure of copper and copper alloy: (1) rare earth compounds with high melting point, high thermal stability and small specific gravity are formed with strong affinity between rare earth and oxygen and sulfur, in addition, rare earth elements can easily react with atomic hydrogen to form RH2 or RH3 stable hydrides (R stands for rare earth metals) , which are dissolved in copper alloys in the form of solid solution, thus eliminating the harmful effects of hydrogen. (2) rare earth, PB, BI and other elements form intermetallic compounds with higher melting point than copper, so it is possible to keep solid state in the process of copper melting and casting and to remove PB and Bi from liquid copper alloy together with molten slag.

02, the effect of re on the microstructure of copper and copper alloy is mainly the effect of refining grain, reducing or eliminating columnar crystal and enlarging equiaxed crystal region. There are three viewpoints about the mechanism of rare earth refining copper and copper alloy: 

(1) forming new crystal nucleus and restraining grain growth. 

(2) microcrystallization.

 (3) alloying.

03 effect of rare earth on the structure of inclusion the effect of rare earth on the structure of inclusion is mainly to change the shape and distribution of impurity. There are four main types: 

(1) reducing or eliminating dendritic crystal and columnar crystal in the alloy structure. 

(2) some impurities in the alloy are in the form of bars, sheets or even blocks, thus improving or improving the mechanical and processing properties of copper and its alloys. 

(3) some harmful impurities in the alloy can be redistributed on the micro-volume of the metal or affect the macro-segregation of some impurities, so that the properties of the alloy can be improved. 

(4) the compounds containing rare earth are adsorbed on the grain boundary of the metal or alloy, thus reducing the amount of harmful impurities in the alloy grain boundary with low melting point, thus weakening the high temperature temper embrittlement of the alloy.

3. Effect of rare earth on properties of copper and copper alloys 01 effect on workability the casting properties of copper and copper alloys can be improved by adding proper amount of rare earth metals into copper alloys. For different kinds of copper alloys, the fluidity can be increased by 30% ~ 40% when rare earth is added. The addition of 0.01% ~ 0.03% mixed rare earth can improve the elongation at high temperature, improve the hot working property, and reduce or eliminate the hot rolling cracking. The strength of grain boundaries and the number of brittle phases are increased and the high temperature σb and δ of copper alloy are increased by the removal of impurities. The addition of re can reduce the residual stress and increase the cold deformation ability of the material within a certain deformation degree (& Lt; 14%) . 02 The influence of re and cu on wear resistance can form intermetallic compounds with high hardness and uniform distribution, which become the resistance of dislocation movement Moreover, rare earth can effectively improve the form and distribution of inclusions, reduce the possibility of weakening grain boundary, reduce the probability of cracking along grain boundary under load, and thus improve the wear resistance. The cast brass containing rare earth has high hardness, good plasticity and toughness, which can shorten running-in period, prolong stable wear period, thus reduce wear and prolong the service life of the work piece. ADDING CE and B to high manganese aluminum bronze can reduce dry friction and wear by 20% and lubricating friction and wear by 50% . 03 on mechanical properties and electrical conductivity the effect of rare earth on mechanical properties of copper and copper alloys is mainly manifested in hardness, strength, plasticity and so on. When the content of rare earth in pure copper is 0.1% ~ 0.2% , the strength increases greatly, but the strength increases slowly when the content is higher than 0.2% . The mechanism of the effect of rare earth on the conductivity of copper and copper alloys is generally believed to be: on the one hand, the refinement of rare earth causes the grain refinement of copper, the increase of grain boundary and the increase of electric scattering probability, leading to the increase of resistivity and the decrease of conductivity; on the other hand, the impurity, lattice distortion, electron scattering and conductivity of copper are reduced by rare earth purification.

4. Conclusion rare earth elements in copper and copper alloys can purify, refine and change the distribution of inclusions, thus improving the processing properties, corrosion resistance, wear resistance, mechanical properties and electrical conductivity, therefore, it is expected that rare earth will improve the properties of copper and copper alloys. At present, many copper and copper alloy materials containing rare earth elements have been successfully developed, but more copper and copper alloys have not been used with rare earth elements, therefore, it is necessary to develop more new copper and copper alloy materials containing rare earth elements, so that the application range of rare earth elements in copper and copper alloys will be wider and industrial production can be achieved. The types of rare earth additive or master alloy products need to be more serialized, and the parameters such as adding method and process conditions need to be more perfect. At present, many researches are still in the experimental stage. The mechanism of rare earth improving the properties of copper and copper alloys, the law of influence, and the key technology need to be further discussed. In order to give full play to the advantage of rare earth resources in our country, it is necessary to strengthen the applied research and basic theory research of rare earth in copper and copper alloy, in order to promote the application technology of rare earth and expand the application range of rare earth. 

Source: Rare Earth Center

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