Microstructures and properties of Sn-Ag-Cu lead-flee solder alloys containing La

Trace amounts of La were utilized to improve the melting behaviors, microstructures, tensile properties and microhardness of Sn-3.0Ag-0.5Cu lead-free solder alloy. La has little effect on the melting behavior of Sn-3.0Ag-0.5Cu alloy according to the differential thermal analysis （DTA） tests. The X-ray diffraction （XRD） patterns show that β-Sn, Ag3Sn and Cu6Sn5 coexist in the as-cast solder alloys and LaSn3 phases emerge when adding 0.4% La. The microstructures modified by La are more uniform and much finer than that of baseline alloy, and the coarse LaSn3 particles with complex dendrites are observed by optical microscopy （OM） and scanning electron microscopy （SEM） when the addition of La is up to 0.4%. The composition of the LaSn3 phases is identified by energy-dispersive spectroscopy （EDS）. There are considerable improvements in mechanical properties with 0.05% and 0.1% addition, but degenerations by adding 0.4%La. The Vickers microhardness of β-Sn and eutectic area are both enhanced with the addition of La and the microhardness of LaSn3 is much larger than those of β-Sn and eutectic area.     

时效对含Sc的Al-Cu-Li-Zr合金腐蚀行为的影响

研究了一种含Sc的Al-Cu-Li-Zr合金在不同时效状态下的晶间腐蚀和剥落腐蚀行为.结果表明：不同时效温度下峰时效态合金的晶间腐蚀和剥落腐蚀倾向随着时效温度的升高而增加；在160℃下时效，合金的晶间腐蚀和剥落腐蚀倾向随着时效时间的延长而增加.含Sc的Al-Cu-Li-Zr合金在EXCO溶液中进行的极化曲线测试结果也表现出相同的腐蚀趋势.微观组织观察分析表明，T1（Al2CuLi）相和无沉淀析出带（PFZ）是引起合金腐蚀敏感性增加的主要因素.     

Flow stress behavior of Al-Cu-Li-Zr alloy containing Sc during hot compression deformation

The flow stress behavior of Al-3.5Cu-1.5Li-0.25（Sc＋Zr） alloy during hot compression deformation was studied by isothermal compression test using Gleeble-1500 thermal-mechanical simulator. Compression tests were preformed in the temperature range of 653-773 K and in the strain rate range of 0.001-10 s^-1 up to a true plastic strain of 0.7. The results indicate that the flow stress of the alloy increases with increasing strain rate at a given temperature,and decreases with increasing temperature at a given imposed strain rate. The relationship between the flow stress and the strain rate and the temperature was derived by analyzing the experimental data. The flow stress is in a hyperbolic sine relationship with the strain rate,and in an Arrhenius relationship with the temperature,which imply that the process of plastic deformation at an elevated temperature for this material is thermally activated. The flow stress of the alloy during the elevated temperature deformation can be represented by a Zener-Hollomon parameter with the inclusion of the Arrhenius term. The values of n,α and A in the analytical expressions of flow stress σ are fitted to be 5.62,0.019 MPa^-1 and 1.51×10^16 s^-1,respectively. The hot deformation activation energy is 240.85 kJ/mol.     

含钪Al-Cu-Li-Zr合金的抗晶间腐蚀和剥落腐蚀性能

通过晶间腐蚀、剥落腐蚀和极化曲线试验,结合扫描电镜和透射电镜等分析手段,研究了含钪Al-Cu-Li-Zr合金在不同时效状态下的晶间腐蚀和剥落腐蚀行为.结果表明,合金在自然时效状态下具有较好的抗晶间腐蚀和剥落腐蚀能力,但随着时效时间的延长,其晶间腐蚀与剥落腐蚀倾向逐渐增加;在4.0 mol/L NaCl 0.1 mol/L HNO3 0.4 mol/L KNO3(EXCO)溶液中进行的极化曲线测试也表现出相同的趋势.透射电镜观察表明,自然时效态合金未析出Г1相,欠时效态合金中有少量细小短棒状Г1相析出,随着时效时间的延长,Г1相逐渐粗化,过时效时合金中出现较宽的无沉淀带(PFZ).由于合金中Г1相和PFZ的开路电位都比铝基体低,在腐蚀过程中作为阳极相优先溶解,从而引起合金晶间腐蚀和剥落腐蚀.     

含Sc超高强Al-Zn-Cu-Mg-Sc-Zr合金的热压缩变形流变应力

采用Gleeblel500热模拟机在应变速率为0.001～10/s、温度为380～470℃、真应变为0～0.7的条件下,研究了实验合金的流变应力行为.结果表明:该合金热压缩变形时存在较明显的稳态流变特征,当ε<1/s时,流变应力开始随应变增加而增加,达到峰值后趋于平稳,呈动态回复特征;当ε≥1/s时,流变应力均出现了明显的峰值应力,为连续动态再结晶特征.带Zener-Hollomon参数的双曲正弦函数可描述合金高温变形时的流变应力,σ解析表达式中A、α和n值分别为5.952×108/s、0.021 MPa-1和5.397:热变形激活能Q为157.9kJ/mol.     

时效对含Sc的Al-Cu-Li-Zr合金腐蚀行为的影响

研究了一种含Sc的Al-Cu-Li-Zr合金在不同时效状态下的晶间腐蚀和剥落腐蚀行为.结果表明:不同时效温度下峰时效态合金的晶间腐蚀和剥落腐蚀倾向随着时效温度的升高而增加;在160℃下时效,合金的晶间腐蚀和剥落腐蚀倾向随着时效时间的延长而增加.含Sc的Al-Cu-Li-Zr合金在EXCO溶液中进行的极化曲线测试结果也表现出相同的腐蚀趋势.微观组织观察分析表明,T1(Al2CuLi)相和无沉淀析出带(PFZ)是引起合金腐蚀敏感性增加的主要因素.     

Al-Cu-Mg-(Ag/Li)合金中析出相的研究进展

Al-Cu-Mg系铝合金具有较高的强度和良好的耐热性能,被广泛用于航空航天材料.微量Ag、Li的添加及复合添加能够改善Al-Cu-Mg系合金的性能,而析出相对合金的性能起决定作用.介绍了微量Ag、Li的添加及复合添加对Al-Cu-Mg合金析出相的影响,重点分析了不同析出相的结构特征、形成条件以及析出序列,并提出了存在的问题及应用前景.     

La对Sn-Ag-Cu无铅钎料与铜钎焊接头金属间化合物的影响

研究微量稀土La在钎焊和时效过程中对Sn-3.0Ag-0.5Cu无铅钎料与铜基板的钎焊界面及钎料内部金属间化合物(IMC)的形成与生长行为的影响.结果表明:钎焊后钎焊界面形成连续的扇形Cu6Sn5化合物层,其厚度随La含量的增加而减小;在150℃时效100h后,连续的Cu3Sn化合物层在Cu6Sn5化合物层和铜基板之间析出,且Cu6Sn5层里嵌有Ag3Sn颗粒;界面金属间化合物总厚度随时效时间的延长而增厚,且在相同时效条件下随La含量的增加而减小;时效过程中金属间化合物生长动力学的时间系数(n)随着La含量的增加逐渐增大;钎焊后钎料内部Ag仍以共晶形式存在,时效后Ag3Sn颗粒沿钎料内部的共晶组织网络析出.     

新型Al-Cu—Li-（Sc＋Zr）合金的剥蚀行为

研究了一种新型Al-Cu-Li-(Sc+Zr)合金在不同时效状态下的剥蚀行为.结果表明:合金在自然时效状态下具有较好的抗剥落腐蚀能力,在160℃下时效,随着时效时间的延长,合金剥落腐蚀敏感性逐渐增加.透射电镜(TEM)观察发现:合金主要析出相为T1相;随着时效时间延长,T1相逐渐粗化,在晶界处还会出现无沉淀析出带(PFZ)及平衡相.合金腐蚀对比实验后,TEM微观腐蚀形貌表明,T1相和PFZ是引起合金剥蚀敏感性的主要因素,腐蚀从T1相的溶解开始,中、后期则以PFZ的溶解为主.     

La对Sn-Ag-Cu无铅钎料组织与性能的影响

研究了微量稀土La对Sn-3.0Ag-0.5Cu无铅钎料显微组织、力学性能、断口形貌、润湿性能和熔点的影响.结果表明:La的质量分数为0.1%可使钎料合金晶粒细化,并显著提高钎料合金力学性能和润湿性能;添加La的质量分数为0.4%将形成粗大LaSn3初生枝晶相,降低力学性能和润湿性能;微量La使钎料合金的熔点轻微增加.