新型易切削黄铜冷拉态微观组织及性能研究

选择以Cu-Zn-Si-P作为基础合金,通过添加适量的铝、锡、镍、镧等合金元素,研制出一种新型易切削黄铜,来替代有毒的铅黄铜和昂贵的铋黄铜,同时在此基础上探讨了各合金元素的加入对合金组织结构和性能的影响,并分析了其影响机理.对Cu-Zn-0.5%Si-P-Sn-Ni-La合金挤压态进行性能检测显示,冷拉态切削性能到HPb59-1的80%左右,其硬度值为165HB,抗拉强度为617 MPa,伸长率为16%.     

无铅磷钙黄铜的组织与性能

通过熔铸方法,于中频感应炉中制备无铅磷钙黄铜铸锭,利用扫描电镜、电子能谱仪、电子万能试验机及卧式车床等手段,研究磷钙黄铜合金的显微组织和力学、切削及耐脱锌腐蚀性能,并结合切屑的形貌观察,分析金属间化合物对切削性能的改善作用。结果表明:磷、钙显著改变了黄铜的组织与性能,使得磷钙黄铜的组织由α相、β相和分布在晶界上及晶粒内的金属间化合物颗粒组成;无铅磷钙黄铜合金的主要成分(质量分数)为57%~60%Cu、40%Zn、0.7%P、0.5%Ca时,合金显示出优良的综合性能,其抗拉强度为362.7 MPa,伸长率为15.0%,布氏硬度为105.0HB,耐脱锌腐蚀深度为321.9μm,切削性能与铅黄铜HPb59-1相当。     

铸轧黄铜薄带组织模拟与性能分析

利用ProCAST软件的CAFE模块,研究了工艺参数对铸轧黄铜薄带凝固组织的影响,并通过自制的双辊铸轧机制备了黄铜薄带,分析了黄铜薄带的组织、硬度与力学性能。结果表明,工艺参数通过影响Kiss(凝固点)高度,来影响柱状晶晶粒尺寸与压下率,Kiss点越高,压下率越大,柱状晶生长空间越大,晶粒尺寸越大。通过改变形核参数可获得较大的压下量与细小的凝固组织,提高板带品质;铸轧黄铜薄带的伸长率可达33%,抗拉强度为430MPa,硬度(HV)为140,退火后黄铜薄带的伸长率为55%,抗拉强度为340MPa,硬度(HV)为75。     

无铅易切削铜合金

根据金属材料的切削机理和铜合金的基本性质,阐述无铅易切削铜合金成分选择的基本思路,提出以弥散分布的金属间化合物代替易切削铅黄铜中的铅或无铅铋黄铜中的铋,从而实现易切削黄铜的无铅化。详细介绍国外无铅易切削铋黄铜研究开发的一些成果和石墨/铜合金复合材料的研究情况,总结国内无铅易切削铜合金的研究情况,结合自己的研究结果,指出无铅易切削铜合金的研究方向是采用适当的元素形成脆而不硬的金属间化合物,并采用一定的加工手段使其呈弥散分布。     

化学镀锡钎料钎焊黄铜的接头组织和力学性能

采用化学镀方法在BAg45CuZn钎料表面镀覆微米锡层,并用镀锡银钎料以火焰钎焊工艺连接H62黄铜。借助金相显微镜、扫描电镜(SEM)和X射线衍射仪(XRD)分别分析锡化学镀层、H62黄铜钎焊接头的显微组织和物相,并利用万能拉伸机和SEM表征钎焊接头的抗拉强度和断口形貌。结果表明,锡化学镀层结晶晶粒呈现明显的(110)、(210)择优取向,化学镀锡银钎料连接的接头中母材与钎缝结合紧密,接头组织中富Cu相减少,出现Cu_5Zn_8化合物相。随着基体钎料表面镀锡含量升高,钎焊接头的抗拉强度呈现先升高后降低趋势。在化学镀锡含量为6.0%(质量分数)时,钎焊接头的抗拉强度为353MPa。镀锡前后钎焊接头的拉伸断口均呈现韧性断裂。     

铅黄铜HPb59-1连续切削的颤振及其特征研究

试验研究了铅黄铜HPb59-1材料在连续切削加工时产生的切削颤振,得到了切屑形成频率与切削用量之间的关系,以及切削颤振形成频率和振幅。试验结果表明,铅黄铜HPb59-1材料因切削加工过程中周期性地产生剪裂型切屑而产生切削颤振。并由此总结得到铅黄铜HPb59-1材料加工产生的切削颤振所具有的一般性特征。     

冷拉拔变形量对Cu-Al2O3弥散强化铜合金线材组织性能的影响

对退火态Cu-0.2%Al₂O₃弥散强化铜合金进行最大变形量达99％的冷拉拔加工,采用光学显微镜、扫描电镜、X射线衍射仪和拉伸试验机等测试手段,研究了冷拉拔变形量对合金微观组织、织构、导电率及力学性能的影响规律。结果表明:随着冷拉拔变形量的增加,合金的微观组织由较粗的长条形组织变成细长的纤维组织,并且经过大变形量冷拉拔加工后部分Al₂O₃颗粒发生了破碎;当变形量为0%时,合金的织构由黄铜织构{011}<211>和立方织构{001}<100>组成,冷拉拔变形量达到60%后,部分立方织构和黄铜织构逐渐转变为高斯织构{011}<100>和铜型织构{112}<111>;冷拉拔变形量对合金导电率几乎没有影响;合金的显微硬度从141 HV0.3增加到161 HV0.3,而合金的抗拉强度由492 MPa增加到637 MPa,屈服强度由452 MPa增加到605 MPa,伸长率由14.0%下降至1.0%,并且发现合金拉伸断裂为韧性断裂。研究结果表明Cu-0.2%Al₂O₃弥散强化铜合金具有较优良的塑性加工性能。     

Effect of friction welding condition on joining phenomena and joint strength of friction welded joint between brass and low carbon steel

Abstract

This paper describes the effect of friction welding condition on joining phenomena and joint strength of friction welded joints between copper–zinc alloy (brass) and low carbon steel (LCS). When the joint was made at a friction pressure of 30 MPa with a friction speed of 27·5 s^?1, brass transferred to the half radius region of the weld interface on the LCS side. Then, transferred brass extended towards the almost whole weld interface with increasing friction time. The joint efficiency increased with increasing friction time, and then the joint obtained 100% and the brass base metal fracture when the joint was made with a friction time of 4·2 s or longer. However, the fact that all joints had some cracks at the periphery portion of the weld interface was due to a deficiency of transferred brass at the periphery portion on the weld interface of the LCS side. On the other hand, brass transferred to the peripheral region of the weld interface on the LCS side, and then transferred towards the entire weld interface when the joint was made at a friction pressure of 90 MPa with a friction speed of 27·5 s^?1. The joint efficiency increased with increasing friction time, and it reached 100% at a friction time of 1·5 s or longer. In addition, all joints fractured from the brass base metal with no cracking at the weld interface. To obtain 100% joint efficiency and the brass base metal fracture with no cracking at the weld interface, the joint should be made with opportune high friction pressure and friction time at which the entire weld interface had the transferred brass.     

VW63Z铸造镁合金线型分离性能及切割机理研究

针对航天飞行器领域对镁合金线型分离特性的需求,开展了VW63Z镁合金聚能切割性能研究。对不同力学性能的VW63Z镁合金试板进行线型分离切割试验,研究了抗拉强度和伸长率对聚能切割性能的影响,并分析了线型聚能切割机理。研究表明,力学性能通过影响试样的侵彻深度来影响材料的线型分离性能。镁合金伸长率小于6%时,抗拉强度对线型分离性能的影响较弱,而伸长率严重影响着线型分离性能。随着伸长率增加,切割分离试板的侵彻深度逐渐降低,不利于材料的线型聚能切割分离。当材料伸长率小于6.5%,抗拉强度小于352MPa时能稳定实现7.2mm切割厚度镁合金试板的线型切割分离。     

Cross-sectional structure,microstructure and mechanical property evolutions of brass cladding pure copper stranded wire composite during drawing

A solid/liquid continuous casting and composite technology was used to produce d8.5 mm brass cladding pure copper stranded wire composite billet and the composite billet was then drawn. The results showed that the composite billet had good surface quality, metallurgical bonding interface between brass and pure copper as well as elongation of 53.1%. Synergistic deformation degree between pure copper wire and brass cladding layer was high during drawing. With an increase of the total deformation amount, the plastic deformation of the pure copper wire reduced triangular arc gaps between the pure copper wires and the triangular arc gaps were fully filled at 50%. When the total deformation amount was increased to 63%, dislocation cells and microbands successively formed in the pure copper wire. In the brass cladding layer, planar dislocation networks, twins and shear bands formed successively, and the main deformation mechanisms were dislocation sliding, twinning and shear deformation. The tensile strength increased from 240 MPa of the composite billet to 519 MPa of the one with the deformation amount of 63%, but the elongation decreased from 53.1% to 3.2%. A process of solid/liquid continuous casting and composite forming→drawing can work as a new compact method to produce brass cladding pure copper stranded wire composite as railway through grounding wire.     

BAg17CuZnSn-xCe钎料组织及性能分析

通过向BAg17CuZnSn钎料中添加微量的稀土元素Ce，研究了微量Ce元素的添加对低银钎料组织及焊接性能的影响.结果表明，当Ce元素质量分数为0.15%时，BAg17CuZnSn-0.15钎料在黄铜和不锈钢母材表面铺展面积较BAg17CuZnSn钎料分别提高了12.1%和37.4%，钎焊接头的抗剪强度达到最大值340.2 MPa.随着Ce元素的添加，钎料的自腐蚀电位逐渐正移，钎料的耐腐蚀性能得到提升.Ce元素对BAg17CuZnSn-xCe钎料基体中的CuZn化合物相有明显的细化作用，当Ce元素质量分数为0.15%时，钎料组织最为细小、均匀.但是当Ce元素质量分数达到0.5%时，钎料中出现了Ce-Sn化合物相.     

Strengthening mechanisms in a high-strength bulk nanostructured Cu–Zn–Al alloy processed via cryomilling and spark plasma sintering

A bulk nanostructured alloy with the nominal composition Cu–30Zn–0.8Al wt.% (commercial designation brass 260) was fabricated by cryomilling of brass powders and subsequent spark plasma sintering (SPS) of the cryomilled powders, yielding a compressive yield strength of 950 MPa, which is significantly higher than the yield strength of commercial brass 260 alloys (～200–400 MPa). Transmission electron microscopy investigations revealed that cryomilling results in an average grain diameter of 26 nm and a high density of deformation twins. Nearly fully dense bulk samples were obtained after SPS of cryomilled powders, with average grain diameter 110 nm. After SPS, 10 vol.% of twins is retained with average twin thickness 30 nm. Three-dimensional atom-probe tomography studies demonstrate that the distribution of Al is highly inhomogeneous in the sintered bulk samples, and Al-containing precipitates including Al(Cu,Zn)–O–N, Al–O–N and Al–N are distributed in the matrix. The precipitates have an average diameter of 1.7 nm and a volume fraction of 0.39%. Quantitative calculations were performed for different strengthening contributions in the sintered bulk samples, including grain boundary, twin boundary, precipitate, dislocation and solid-solution strengthening. Results from the analyses demonstrate that precipitate and grain boundary strengthening are the dominant strengthening mechanisms, and the calculated overall yield strength is in reasonable agreement with the experimentally determined compressive yield strength.     

黄铜静态腐蚀脱Zn层引起拉应力的研究

研究了黄铜在静态腐蚀表面疏松层的应力状态,通过测量自由端挠度的变化及用ＳＥＭ技术测量脱Ｚｎ层的厚度,计算了在脱Ｚｎ层和基体界面处生产的拉应力,其稳定值约等于黄铜屈服强度的１／５,在ＳＣＣ过程中这个附加的拉应力将协助外应力促进位错发射和运动,从而ＳＣＣ裂纹形核。     

黄铜/钢扩散复合双金属界面组织与性能

用扫描电镜、能谱分析和压剪试验等方法,研究了扩散退火温度与时间对黄铜/钢扩散复合双金属界面附近组织、成分和界面结合强度的影响.结果表明,通过扩散复合可使黄铜/钢界面实现良好的冶金结合;在一定温度和时间范围内,随扩散温度和时间的增加界面结合面积增大,结合强度增加,可达220MPa;界面附近发生了原子的互扩散,界面上无有害相生成.     

环保铋黄铜中各元素含量对切削性能的影响

研究环保Bi黄铜中各元素含量对切削性能的影响,对合理选择其化学成分具有重要的意义。试验表明,随着Cu含量的提高其切削性能逐渐下降;随着Bi含量的提高其切削性能逐渐提高;随着稀土含量的增加其切削性能先减少后增加,且稀土含量在0.03%和0.09%时的效果相同。     

铟对低银Ag-Cu-Zn钎料显微组织和性能的影响

研究了低银Ag-Cu-Zn钎料(ωAg≤20%)的熔化特性、铺展性能、钎料显微组织。以黄铜/304不锈钢作为母材,采用火焰钎焊方法,进行了搭接钎焊试验。结果表明,低银Ag-Cu-Zn钎料显微组织主要由铜基固溶体、银基固溶体、Cu Zn化合物相构成。In的添加降低了Ag-Cu-Zn钎料的固、液相线温度,改善了钎料润湿性能;添加In的低银Ag-Cu-Zn钎料在凝固过程中析出富In的银基固溶体,起到了固溶强化的效果,改善了钎焊接头的显微组织,从而提高了钎缝接头的力学性能。使用17Ag Cu Zn-1In火焰钎焊黄铜/304不锈钢,钎焊接头成形美观、组织致密、无缺陷存在,综合性能与含银量为25%的BAg25Cu Zn Sn银钎料的性能相当,节银效果显著。     

2195-T6铝锂合金搅拌摩擦焊接头微观组织结构与力学性能

采用冷源辅助搅拌摩擦焊对2 mm厚的HSn70-1锡黄铜进行对接焊接,并获得了无缺陷的焊接接头. 利用光学显微镜、电子背散射衍射、透射电子显微镜和拉伸试验,分析搅拌区的微观组织及其对强化机制和应变硬化行为的影响. 结果表明,干冰乙醇混合物的快速冷却作用不仅消除了热影响区,还抑制了搅拌区的位错回复和晶粒长大. 搅拌区呈现具有较高位错密度的超细晶结构,搅拌区的抗拉强度为486 MPa,比母材提高了53.8%,断后伸长率也达到了30%,搅拌区屈服强度较母材提高了47.1%,其强化机制主要为固溶强化和晶界强化,但搅拌区的应变硬化行为主要受晶粒尺寸和位错密度的影响. 由拉伸过程中产生的纳米尺度变形孪晶可协调塑性变形,并有效缓解应力集中,使搅拌区强度提高的同时仍具有良好的延展性.

     

易切削黄铜的研究现状及其机理浅析

传统的易切削铅黄铜中含有的铅元素对环境和人都有极大的危害,所以急需寻找一种或者多种元素来替代易切削铅黄铜中的铅.本文介绍了易切削黄铜的发展现状,并经过对比分析其性能了解几种有发展前景的易切削黄铜.从易切削黄铜的切削特点出发研究其易切削的本质,并通过添加微量元素如Ni、P、Ca等,以及稀土元素Ce来改善黄铜的切削性能,达到易切削黄铜低铅或者无铅的目的.     

Sn、Bi微合金化对6026铝合金组织、力学与切削性能的影响

以Sn、Bi替代Pb,制备了无Pb易切削6026铝合金。利用光学显微镜、扫描电镜、拉伸试验机和高速车床,研究了Sn、Bi微合金化对6026铝合金显微组织、力学性能与切削性能的影响。结果表明,单独添加Bi元素的6026铝合金由α-Al基体、Mg₂Si和CuAl₂强化相以及低熔点单质Bi相组成;复合添加Sn、Bi元素的6026铝合金由α-Al基体、Mg₂Si和CuAl₂强化相以及低熔点SnBi共晶相组成,且铝合金具有更好的切削加工性能,切屑尺寸更细小,抗拉强度,屈服强度和伸长率分别为358.3 MPa,295.7 MPa和13.9%。     

基于ANSYS Workbench金刚石圆锯片的力学分析

建立了干切金刚石圆锯片有限元分析模型,利用有限元软件ANSYS Workbench对高速旋转切削金刚石圆锯片进行应力分析。得出圆锯片在受离心力、锯切力和热载荷作用下的应力大小及分布规律。结果表明:根据第三强度理论,锯片干切时产生的应力为535 MPa,已经超出其安全许用应力,所以影响锯片寿命的最大因素是锯切热引起的热应力。离心力与锯切力共同作用时,能使径向热应力减小约3%,同时也会使切向热应力的压应力增大约0.4%。