高强导电Cu-3Ti-0.1Mg-0.05B-0.05La合金的微观组织与性能

Microstructure and properties of a novel Cu–3Ti–0.1Mg–0.05B–0.05 La alloy with high strength and conductivity

采用真空熔铸和冷开坯工艺,通过优化形变热处理工艺,调控基体晶粒尺寸、第二相的析出及分布状态,制备出综合性能优异的Cu-3Ti-0.1Mg-0.05B-0.05La合金.结果表明,经过400℃/2 h一次时效处理后,Cu-3Ti-0.1Mg-0.05B-0.05La合金的显微硬度可达356 HV,此时导电率为14.5%IACS.透射电镜分析表明,Cu-3Ti-0.1Mg-0.05B-0.05La合金第二相的析出演变规律为富Ti相→颗粒状β′-Cu_(4)Ti相→颗粒状β′-Cu_(4)Ti相+片层状β-Cu_(4)Ti相→片层状β-Cu_(4)Ti相,其中颗粒状β′-Cu_(4)Ti相是最重要的强化相,片层状β-Cu_(4)Ti相会导致合金强度下降,但可以提高导电率.采用二次时效能够进一步优化Cu-3Ti-0.1Mg-0.05B-0.05La合金的综合性能,在合金强度基本不变的条件下,显著提升了合金的导电率.450℃/8 h一次时效+50%冷轧+400℃/1 h二次时效处理后合金的显微硬度和导电率分别达到了341 HV和20.5%IACS.

The Cu-Ti alloy has similar mechanical properties and electrical conductivity to the Cu-Be alloy.It also exhibits excellent high-temperature properties and stress relaxation resistance.Therefore,it has emerged as a promising material to replace the toxic Cu-Be alloy.With the technological advances,the new generation of connector materials put forward higher requirements for performance,such as strength over 1000 MPa and conductivity over 15%IACS.However,it is difficult to obtain Cu-Ti alloys with such high strength and conductivity.An effective way is to increase the aging temperature or prolong the holding time of the alloy.When the strength of the alloy is reduced,the increase in cost is inevitable.The refining of grains or the regulation of size and distribution of precipitates has proved more effective,which is also true for Cu-Ti alloys.Currently,the refined grain size is still 10-50μm achieved through a series of common processing methods,including hot rolling,solid solution,and cold rolling.Therefore,the improvement of strength and conductivity is limited for the Cu-Ti alloy.This paper provides a preparation method for synchronously improving the strength and conductivity of the Cu-Ti alloy.The Cu-3Ti-0.1Mg-0.05B-0.05La alloy with an ultra-fine grain structure is obtained via the vacuum casting and cold billet opening.The secondary aging process is used to adjust the size and distribution of the second phase to obtain a Cu-Ti alloy strip with high strength and good conductivity.The results show that the Cu-3Ti-0.1Mg-0.05B-0.05La alloy displays the maximum microhardness of 356 HV and a conductivity of 14.5%IACS after aging at 400℃/2 h.The relationship between the second phase precipitation and properties of the Cu-3Ti-0.1Mg-0.05B-0.05La alloy was analyzed using TEM(Transmission electron microscope).The evolution of the second phase is the Ti-rich phase→the granular phaseβ′-Cu_(4)Ti phase→the granularβ′-Cu_(4)Ti phase+lamellarβ-Cu_(4)Ti phase→the lamellarβ-Cu_(4)Ti phase.The granularβ′-Cu_(4)Ti phase is the most important strengthening phase;the lamellarβ-Cu_(4)Ti phase can decrease the strength of the alloy but increase the conductivity.The comprehensive properties of Cu-3Ti-0.1Mg-0.05B-0.05La alloy can be further optimized by the secondary aging process.The microhardness and electrical conductivity of the Cu-3Ti-0.1Mg-0.05B-0.05La alloy reach 341 HV and 20.5%IACS after the primary aging at 450℃/8 h+50%cold rolling+secondary aging at 400℃/1 h.