Effect Of La Microalloying On The Microstructure And Properties Of Copper Pipe

Taking use of the micro-alloying principle,the rare earth element La was added into the pure copper.The microstructure and properties of the as-cast copper micro-alloyed with different content of La were explored to choose optimum content of the micro-alloyed pure copper.According to the results of this research,Thermal performance of the as-cast pure copper micro-alloyed with La at the content of0.089 wt.% was tested.Then the room temperature formability of the as-cast copper billets of TP2,Tu and Cu-La alloy were studied.At last the micro-alloyed TP2 copper tubes with related content of La wsa produced under the environment of industrial production,and it’s performance was tested.The analytical test of the as-cast pure copper shows that the addition of La can effectively purify the structure and refine the grain of copper.It shows that with the increase content of La,the microstructure of the as-cast pure copper transformed form coarse columnar grain to fine equiaxed grain.More over,The tensile strength and hardness improved after La addition.But as the La content increased,the elongation of the samples increased first and then decreased.Then the energy spectrum analysis and testing was taken to confirm the existing form of La rich phase in micro-alloyed pure copper,and the result shows that it is the second phase particles Cu6 La.The thermal performance of pure copper billets of TU and micro-alloyed pure copper billets with the content of 0.089 wt.%La was tested.The analysis of microstructure and thermal performance shows that in hot deformation processing the second phase particles Cu6 La had increased work hardening,more over dynamic recrystallization was also suppressed during thermal deformation.And with the increase of the amount of deformation,the dynamic recrystallization grains’ growth was also suppressed by Cu6 La.As a result,this improves thermal performance of pure copper.At the condition of low rate dynamic compression,the room temperature formability of the as-cast copper billets of TP2,Tu and Cu-La alloy were studied.After 50% deformation,the adiabatic shear bands(ASBs)with 45 degrees of compression direction were found in the center region of the samples of TP2 and TU.And the quantity and size increased after 70% deformation.However,there are no or rarely the ASBs in the samples of Cu-La alloy at any amount of deformation.Using backscattered electron scan,it can be found that compared with samples before deformation,there are almost no changes with the morphology and distribution of the second phase particles Cu6 La in deformed Cu-La alloy.Then the characteristics of non deformable particles are determined.The results of micro hardness analysis show that,with further deformation,the microhardness of TP2 and TU samples is obviously improved compared with the as-cast ones.However,the Cu-La alloy has barely improved.A small amount of La was added into the TP2 copper tubes for air conditioning by using Cu-La intermediate alloy.Then the composition and microstructure properties of the copper billets and finished light tubes with La contents of 0ppm and 200 ppm were analyzed.The composition analysis shows that the addition of La can effectively remove the impurity elements;The results of microstructure observation and tensile tests show that compared with the TP2 samples without rare earth elements addition,the grain size of the copper billets and finished light tubes with micro-alloyed La addition is finer.The tensile strength of finished light tubes increases 20%,reaching255 Mpa,and the elongation increases 10%,reaching 55%;Electrical conductivity of the finished light tubes with La addition were tested,the tests show that the electrical conductivity increases 5.07%,reaching 84.69%ICAS.These studies have a high practical reference value in transforming into industrial products.