硬钎焊温度对Cu-Cr-Zr合金组织和力学性能的影响

Effect of Brazing Temperature on Microstructure and Mechanical Properties of Cu-Cr-Zr Alloy

摘要:

Cu-Cr-Zr合金是一种高强高导铜合金,常用于高温、耐磨等复杂环境中关键零部件的制造。以时效硬化后的Cu-1.04Cr-0.16Zr合金为研究对象,采用扫描电镜、拉伸试验机、显微硬度计、体视显微镜研究了硬钎焊温度(600℃～800℃)条件下的Cu-1.04Cr-0.16Zr母材的组织、拉伸性能、显微硬度及断口组织特征,并在此基础上分析了Cu-1.04Cr-0.16Zr合金的高温软化机制。结果表明：Cu-1.04Cr-0.16Zr合金的抗拉强度和显微硬度随钎焊温度的升高而降低,初始抗拉强度为477.32MPa,延伸率为40.13%,显微硬度为151.78HV,当钎焊温度为600℃时,Cu-1.04Cr-0.16Zr合金抗拉强度稍有降低,显微硬度基本不变,表现出良好的抗软化性能；当钎焊温度为650℃时,Cu-1.04Cr-0.16Zr合金开始发生部分再结晶,大等轴晶边界出现一些细小、无畸变的等轴晶粒,晶粒尺寸为2μm～7μm,析出相对晶界的钉扎作用开始减弱,抗拉强度和显微硬度大幅下降；随着钎焊温度的升高,Cu-1.04Cr-0.16Zr合金进一步软化,Cu-1.04Cr-0.16Zr合金内部出现大量的退火栾晶；Cu-1.04Cr-0.16Zr合金在硬钎焊温度条件下均出现颈缩现象,并存在明显的塑性扩展区,随着钎焊温度的升高,断面收缩率逐渐增大,韧窝沿拉伸方向伸展长大,表现出很好的塑性。在满足钎焊接头各项性能的条件下,可采用熔化温度较低的钎焊材料,避免Cu-1.04Cr-0.16Zr合金出现软化现象。

Abstract:

Cu-Cr-Zr alloys are kinds of copper alloys with high strength and high conductivity, which usually apply to the manufacturing of key parts in complex environment such as high temperature and wear resistance. In this paper we studied the microstructure, tensile properties, microhardness, and fracture characteristics of Cu-1.04Cr-0.16Zr alloy at different brazing temperatures (600 ℃―800 ℃) by means of scanning electron microscope, cupping machine, micro-hardness tester, and stereomicroscope. On this basis, the softening mechanism of Cu-1.04Cr-0.16Zr alloy at high temperature was analyzed. The results showed that the ultimate tensile strength (UTS) and microhardness of alloys decreased with the increase of brazing temperature. The UTS , elongation, and microhardness of the samples were about 477.32 MPa, 40.13% and 151.78 HV. When the brazing temperature of Cu-1.04Cr-0.16Zr alloy was 600 ℃, the UTS decreased slightly whereas the microhardness was basically unchanged, and they showed good softening resistance. Partial recrystallization started to occur in the microstructure of Cu-1.04Cr-0.16Zr alloy when the brazing temperature was 650 ℃. Some fine and undistorted equiaxed grains appeared at the boundary of large equiaxed grains, which the grain size was about 2 μm―7 μm. The pinning effect of precipitation on grain boundary began to weaken, the UTS and microhardness decreased significantly. The samples were further softened with the increase of brazing temperature, a lot of annealing twins appeared in the microstructure of Cu-1.04Cr-0.16Zr alloy. Cu-1.04Cr-0.16Zr alloy had necking phenomenon and obvious plastic expansion zones after brazing. The shrinkage of cross section increased gradually with the increase of brazing temperature. The dimples grew along the tensile direction, and Cu-1.04Cr-0.16Zr alloy showed good plasticity. In summary, under the condition of satisfying the properties of the brazed joints, the softening of Cu-Cr-Zr alloys can be avoided by means of brazing filler metals with lower melting temperature.