粉末冶金法制备Al-Pb合金微观组织分析EI

采用机械合金化与真空热压烧结制备Al-Pb合金,并通过热挤压变形细化显微组织。XRD检测分析表明:Al,Pb衍射峰随机械合金化的进行不断宽化,晶粒尺寸减小。SEM分析表明:球磨15h后可以得到合金粉末,其具有Pb粒子弥散分布于Al基体的复相结构。再通过550℃/20MPa真空热压烧结1h,可制备出Al-Pb合金块体。适当的热挤压工艺能够细化组织,减小Pb颗粒的尺寸。其抗拉强度可达231.6MPa,延伸率为17.6%。     

热反挤压变形对n-SiC_p/2024复合材料组织与性能的影响

利用半连续铸造-热反挤压工艺制备了n-SiCp/2024复合材料棒材。通过金相组织观察(OM)、扫描电镜(SEM)、室温力学性能以及电导率测试等手段,研究了该复合材料在热反挤压前后的显微组织、力学性能与电导率的变化情况。结果表明:复合材料铸锭中粗大第二相沿晶界非连续分布,Cu、Mg元素偏聚显著,大多数n-SiCP偏聚在晶界处,少量分布在晶内;热挤压变形后,n-SiCp团聚现象显著消除,Cu、Mg元素及n-SiCP分布趋于均匀,n-SiCp及破碎第二相沿热挤压方向呈纤维状分布;拉伸实验结果表明,热挤压后复合材料的强度及塑性显著提高;热挤压后,复合材料的电导率低于基体合金。     

锌对Sn3.5Ag0.5Cu钎料合金微结构及性能的影响

运用莱卡显微镜、X射线衍射仪等仪器设备,研究了添加元素Zn对Sn3.5Ag0.5Cu钎料合金微结构及性能的影响.结果表明,Zn与Cu、Ag形成化合物AgZn、CuZn3,能显著细化Sn3.5Ag0.5Cu钎料组织;添加元素Zn后的Sn3.5Ag0.5Cu钎料合金的显微硬度提高11%,蠕变抗力也得到明显提高;运用键参数函数理论分析了Zn对Sn3.5Ag0.5Cu钎料合金微结构及性能影响的作用机理.[作者单位].5Cu钎料;组织;性能;键参数函数     

机械合金化Zr-Al-Ni-Cu-Ag非晶合金的晶化行为

研究了机械合金化非晶态Zr65Al7.5Ni10Cu7.5Ag10合金的晶化过程，由于存在扩散不均匀区，机械合金化非晶合金在深过冷液相区的退火组织不同于快淬合金，在深过冷液相区退火，析出二十面体准晶相及一些知相：在靠近第一个放热峰的温度退火，近出Zr2Cu相：第二个放热峰对应残余非晶相及准晶相向Zr2Ni,Zr2-Al3的转变。     

不同晶粒尺寸的三元Cu40Ni40Cr20合金的制备及其显微组织研究

采用电弧熔炼和机械合金化,随后在750℃,58MPa下热压制备了晶粒尺寸差别较大的Cu40Ni40Cr20合金,用X射线衍射仪、扫描电镜等分析手段对比研究了显微组织结构.结果表明:电弧熔炼制备的晶粒尺寸较大的Cu40Ni40Cr20合金为二相,组织极其不均匀;采用机械合金化,通过控制热压条件制备的纳米晶Cu40Ni40Cr20合金仍为双相,但显微组织均匀,稳定.随着球磨时间的延长,由于晶粒细化和应变的结果,衍射峰偏移并有明显的宽化产生,Cu在Cr或Cr在Cu中的固溶度明显增加,当球磨60h后,合金已由双相变成亚稳态的单相.由于机械合金化的粉末处于非平衡态,其超固溶度溶质随热压和真空退火过程的进行会慢慢脱溶分解出来,合金已由单相变为两相,两相颗粒均成倍长大,但仍然保持纳米级尺度;机械合金化、热压和退火后样品中Cu,Ni和Cr的晶格均未发生崎变;讨论了晶粒细化对合金显微组织的影响.     

Al—Li—Mg合金的新制法

外刊报道了研究开发均质、力学性能优异的Al/Li/Mg合金新制法。这种合金经过热挤压后施行时效处理,弹性系数大,密度小,组织细化。最重要的是没有象普通合金那样,氧化物和碳化物在晶界析出后产生晶界裂纹。     

Mg-Zn-xCu-Ce镁合金铸态组织与力学性能

利用光学显微镜(OM)、扫描电子显微镜(SEM)、X射线衍射(XRD)分析了Cu元素对Mg-Zn-xCu-Ce合金铸态组织的影响,并用显微硬度仪测试合金的显微硬度。结果表明:Cu含量的增加可以显著细化晶粒。当Zn,Cu质量比小于1时,合金枝晶间共晶组织由薄层状α-Mg+CuMgZn组成;当Zn,Cu质量比等于1时,合金中出现Mg2Cu相,同时共晶组织开始粗化;随着Cu含量的升高(Cu质量分数大于Zn),合金枝晶间共晶组织由α-Mg+CuMgZn+Mg2Cu组成,在形态上由薄层状转变为蜂窝状。合金的显微硬度随着Cu含量升高而增加。     

Ce对Al-Zn-Mg-Cu合金亚快速凝固铸造组织的影响

通过XRD,DSC,SEM,EDS等现代分析方法,研究了稀土元素Ce在不同凝固冷却速率下对Al-Zn-Mg-Cu合金显微组织、凝固温度的影响,分析讨论了Ce对合金晶粒细化和熔体净化作用的原理。结果表明,合金的主要析出相为α-Al和MgZn_2型共晶相,MgZn_2固溶了Al,Cu,Mg等元素并形成了Mg(Zn,Cu,Al)_2相,在晶界上溶质元素浓度较高,与α-Al基体共晶形成层片状共晶组织。添加Ce能使合金枝晶间距减小,并减小共晶层片间距和细化共晶组织,显著细化晶粒,并抑制铝合金中的杂质相Al7Cu2Fe的出现。Ce还将合金α-Al基体和共晶相的析出温度分别降低了6.4℃和5.6℃。     

Mg-5Yb-0.5Zr变形镁合金的显微组织与力学性能

本文利用熔剂保护法制备了Mg-5Yb-0.5Zr合金,并进行了热挤压和热处理,对合金在各种加工状态下的相结构、显微组织和力学性能进行了试验和测试.结果表明,合金由α-Mg和Mg2Yb相组成,铸态组织中的Mg2Yb相聚集在晶界,并在热挤压过程中被破碎起到限制再结晶和弥散强化的作用;合金经热处理后有一定的时效强化效应,析出相为共轭生长的短棒状Mg2Yb颗粒.合金在挤压态的强度最高,T5态热处理可得到良好的综合力学性能.     

微量Zr、Cd对AlSi7Cu2Mg组织和性能的影响

为提高AlSi7Cu2Mg合金的力学性能,研究了Zr、Cd合金元素对AlSi7Cu2Mg合金显微组织和力学性能的影响。对铝液采用精炼,并利用重力铸造,结果表明：Zr、Cd使合金晶粒细化,改善显微组织;Zr、Cd可以提高合金的抗拉强度和伸长率。     

Simulation of clusters formation in Al-Cu based and Al-Zn based alloys

A Monte Carlo computer simulation is adopted to investigate the role of micro-alloying elements Mg and Ag in Al-Cu and Al-Zn alloys. Small amount additions of Mg to the Al-Cu alloy markedly retard the formation of Cu clusters due to the preferential trapping of free-vacancies available for Cu diffusion. On the other hand, additions of Mg to the Al-Zn alloy promote the formation of Zn clusters due to the preferential Mg-Zn interaction. As for the effect of Ag, it is found that, in both Al-Cu-Mg and Al-Zn-Mg alloys, Ag atoms are preferentially bounded to Mg-Cu-vacancy or Mg-Zn-vacancy complexes. However, in Al-Cu-Mg alloy Ag atoms interact with Mg, while in Al-Zn-Mg alloy they interact with both Mg and Zn.     

新型热处理调控Al-Cu-Mg合金残余应力的工艺和机理

对Al-Cu-Mg合金进行一种能消减残余应力的新型热处理,使用透射电镜(TEM)、扫描电镜(SEM)、X射线衍射等手段分析残余应力并测试力学性能,研究了这种合金的微观组织结构和性能。结果表明:新型热处理使Al-Cu-Mg合金的残余应力消减率达到92.7%(与固溶态铝合金相比),并得到优良的强塑性配合(屈服强度达到463.6 MPa,抗拉强度达到502.5 MPa,伸长率达到12.7%)。微观组织的分析结果表明:在进行新型热处理的合金中S'相比用传统热处理的更为细小、分布更均匀,由S'相析出的共格应力场与淬火残余应力场叠加使合金残余应力大幅度降低,使合金的综合性能较高。     

含Ag的Al-Cu-Mg基合金的断续时效特征

采用维氏硬度、拉伸力学性能测试、扫描电镜和透射电子显微镜分析手段,研究了断续时效对含Ag的Al-Cu-Mg基合金的组织和性能的影响。结果表明:185℃高温欠时效Al-Cu-Mg-Ag合金在低温进行二次时效时,会发生二次析出现象,合金塑性显著提高。随着185℃欠时效时间的延长,合金二次时效初始硬度升高,峰值时间缩短,峰值硬度增量降低。二次时效温度为65℃时,合金中主要强化相为G.P.区和少量的Ω相,其峰值强度硬度低于T6态,提高二次时效温度至150℃,合金主要强化相为Ω相和少量的G.P.区,其峰值强度硬度略高于T6态。     

Effect of Sc and Zr additions on microstructures and corrosion behavior of Al-Cu-Mg-Sc-Zr alloys

The effects of adding the alloy element Sc to Al alloys on strengthening, recrystallization and modification of the grain microstructure have been investigated. The combination of Sc and Zr alloying not only produces a remarkable synergistic effect of inhibition of recrystallization and refinement of grain size but also substantially reduce the amount of high-cost additional Sc. In this work, the microstructures and corrosion behavior of a new type of Al-Cu-Mg-Sc-Zr alloy with Sc/Zr ratio of 1/2 were investigated.The experimental results showed that the Sc and Zr additions to Al-Cu-Mg alloy could strongly inhibit recrystallization, refine grain size, impede the segregation of Cu element along the grain boundary and increase the spacing of grain boundary precipitates. In addition, adding Sc and Zr to Al-Cu-Mg alloy effectively restricts the corrosion mechanism conversion associated with Al2 Cu Mg particles, which resulted in the change of the cross-section morphology of inter-granular corrosion from an undercutting to an elliptical shape. The susceptibility to inter-granular corrosion was significantly decreased with increasing Sc and Zr additions to the Al-Cu-Mg alloy. The relationships between microstructures evolution and inter-granular corrosion mechanism of Al-Cu-Mg-Sc-Zr alloys were also discussed.     

Coupled influence of microstructure and atmosphere environment on fatigue crack path in new generation Al alloys

The fatigue crack propagation behavior of new generation Al alloys developed for aeronautical applications is studied at moderate ΔK and in the near threshold domain. The crack growth rate and the crack path are shown to depend on alloy composition, aging condition and atmosphere environment, and to be governed by the slip morphology. In absence of environment assistance, a crystallographic (1 1 1) faceted cracking leads to a slow stage I-like propagation in Al-Li-Cu alloys and underaged Al-Cu-Mg alloys with microstructure consisting of shareable precipitates or solute cluster structures that promote heterogeneous slip-band formation, which is in contrast with a ductile transgranular featureless stage II crack path in overaged Al-Cu-Mg. In air at moderate ΔK, an adsorption assisted propagation mechanism is assumed to prevail in both Li and Mg bearing materials, water vapor assistance inducing a transgranular stage II regime associated to homogeneous slip generating a flat-facet and step-like features; in the near threshold domain, the same mechanisms is operating for Al-Cu-Mg alloys while even more accelerated growth rates and lower effective threshold for Al-Cu-Li alloys are attributed to an assistance of hydrogen produce from the dissociation of adsorbed water vapor.     

Ageing and toughness of silicon carbide particulate reinforced Al-Cu and Al-Cu-Mg based metal-matrix composites

Metal-matrix composites (MMC) comprising powder aluminium alloys reinforced by particulate ceramic are being developed for widespread aerospace structural applications ranging from fuselage and missile components to undercarriage parts. Most interest is centred on MMCs with an Al-Cu-Mg (2124) matrix alloy. These MMCs possess high levels of specific stiffness with high specific strengths but can exhibit lower ductility and toughness than conventional unreinforced aluminium alloys.To overcome these problems the effects of alloy composition on the ageing behaviour and notched tensile properties of Al-Cu-Mg and Al-Cu based alloys reinforced with 20 wt% silicon carbide particulate have been investigated.Al-Cu-Mg MMCs gave higher strengths and moduli than unreinforced sheet. Lowering the copper and magnesium content resulted in reduced strength but did not affect the rate of age hardening. The Al-Cu-MMCs gave the lowest strengths but the absence of natural ageing may prove advantageous, enabling sheet to be formed and subsequently heat-treted to the peak strength condition.     

微量Ag对CP276合金性能和组织的影响

研究添加不同含量的Ａｇ对ＣＰ２７６合金的拉伸性能和时效组织的影响。对拉伸强度、延伸率测试及透射电镜观察表明：０．１１ｗｔ％加入可促进Ｔ１相析出，使合金强度值升高；０．３５ｗｔ％Ａｇ的加入可在时效前期生成富Ａｇ、Ｍｇ的稳定的ＧＰ区，从而降低合金中Ｃｕ的固溶度，阻碍Ｔ１相析出，时效后期，ＧＰ区分解，生成大量Ｔ１相，使合金强度值显著升高。     

Fabrication of Ti–Nb–Ag alloy via powder metallurgy for biomedical applications

Ti and some of its alloys are widely used as orthopedic implants. In the present study, Ti–26Nb–5Ag alloys were prepared by mechanical alloying followed by vacuum furnace sintering or spark plasma sintering (SPS). The microstructure and mechanical properties of the Ti–Nb–Ag alloys were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDX), compressive and micro-hardness tests. The effect of different sintering methods on the microstructure and properties of Ti–Nb–Ag alloy was discussed. The results showed that the titanium alloy sintered by vacuum furnace exhibited a microstructure consisting of α, β and a small amount of α″ martensite phase; whilst the SPS sintered alloy exhibited a microstructure consisting of α, β and a small amount of α″ martensite phase, as well as a nanostructured Ag homogeneously distributed at the boundaries of the β phases. The Ti–Nb–Ag alloy sintered by SPS possessed fracture strength nearly 3 times of the alloy sintered by vacuum furnace.     

Influences of Ag and Au Additions on Structure and Tensile Strength of Sn-5Sb Lead Free Solder Alloy

It is important, for electronic application, to decrease the melting point of Sn-5Sb solder alloy because it is relatively high as compared with the most popular eutectic Pb-Sn solder alloy. Adding Au or Ag can decrease the onset melting temperature （233℃） of this alloy to 203,5℃ and 216℃, respectively. The results indicate that the Sn-5Sb-i.5Au alloy has very good ultimate tensile strength （UTS）, ductility, and fusion heat, which are better than both those of the Sn-5Sb-3.SAg and Sn-5Sb alloys. The formation of intermetallic compounds （IMCs） AuSn4 and Ag3Sn enhanced the SbSn precipitates in the solidification microstructure microstructure stability, while retained the formation of thus significantly improved the strength and ductility For all alloys, both UTS and yield stress （σy） increase with increasing strain rate and decrease with increasing temperature in tensile tests, but changes of ductility are generally small with inconsistent trends.     

Effects of small amounts of Ni/P/Ce element additions on the microstructure and properties of Sn3.0Ag0.5Cu solder alloy

The purpose of this study is to investigate the effects of small amounts of Ni, P and Ce element additions on the microstructure and properties of Sn3.0Ag0.5Cu solder alloy. The results indicate that adding trace amounts of Ni, P or Ce element has little influence on the melting temperature of Sn3.0Ag0.5Cu solder alloy. Adding Ni or Ce element cannot improve the wettability and anti-oxidization of the Sn3.0Ag0.5Cu solder alloy, but it can depress the interfacial intermetallic compounds growth due to the high temperature aging and then improves the shear strength of the solder joint. In addition, the P element addition not only significantly increases the maximum wetting force and decreases the wetting time of the solder, but also improves the anti-oxidation property of the Sn3.0Ag0.5Cu solder. At the same time, adding P element also increases the hot cracking sensitivity of the solder surface in the solidification. However, it is noted that adding Ni or Ce element can depress the formation of the hot carking. The reason may be related to the modification of the microstructure of the solder alloys due to trace amounts of Ce or Ni elements additions. The adding elements change the microstructure of Sn3.0Ag0.5Cu solder alloy.