添加Bi和P对Sn-0.7Cu无铅钎料合金性能的影响

研究了添加Bi和P对Sn-0.7Cu无铅钎料合金熔点、显微组织、在Cu上的润湿性、导电率、硬度以及蠕变抗力等性能的影响。实验结果显示,随Bi含量增加,Sn-0.7Cu合金的熔点、导电率略有降低,润湿性、抗蠕变性能和维氏硬度均提高;此外,在添加Bi的基础上加P元素,能进一步降低Sn-0.7Cu-Bi合金的熔点,提高合金的导电率和润湿能力,但合金硬度略有下降;Sn-0.7Cu-1Bi-0.05P钎料合金的抗蠕变性优于Sn-0.7Cu-1Bi,Sn-0.7Cu-3Bi-0.05P钎料合金的抗蠕变性则劣于Sn-0.7Cu-3Bi。金相显微组织观察表明,单独加Bi能细化Sn-0.7Cu合金中的Cu6Sn5金属间化合物相;P的加入使Sn-0.7Cu-1Bi合金中的β-Sn枝晶尺寸变小,且Cu6Sn5相呈规则网络状分布于枝晶间隙;而在Sn-0.7Cu-3Bi合金中加P则粗化了Cu6Sn5相,并使IMC呈无规则分布。     

C194合金连续挤压全过程的组织与性能演变

采用光学显微镜、透射电子显微镜(TEM)、维氏硬度仪和万能材料试验机等手段对C194合金连续挤压全过程的组织演变与性能特征进行研究。结果表明,C194合金连续挤压过程没有出现明显的动态再结晶组织,仅在直角弯曲后变形区观察到少量沿晶界择优析出的不完全动态再结晶细小晶粒;各变形区硬度随变形量的增加由88.7HV提升至136.1HV,并在直角弯曲后变形区增长减缓;挤压前后材料抗拉强度由263 MPa提高到476 MPa,延展性则由26.5%降至18.7%;挤压过程中发生第二相析出,析出物呈现尺寸为60~80nm的椭球形和尺寸为10~20nm且弥散分布的微小颗粒两种形貌。     

温度和加载率对Sn-58 Bi合金力学性能影响试验研究

通过不同温度和加载率下拉伸试验,获得了Sn-58％(质量分数)Bi共晶合金的弹性模量、拉伸强度、断裂应变等主要力学参数;结合断口微观组织的观测,对Sn-58％Bi共晶合金拉伸变形特性进行了研究.分析了加载率和温度对Sn-Bi合金变形行为的影响.试验结果分析表明,合金延展性随温度升高而增大,随加载率增大而显著减小.断口微...     

累积连续流变挤压对Al-Mg(-Mn-Fe)合金组织性能影响

目的 研究多道次累积连续流变挤压变形对Al-Mg(-Mn-Fe)合金组织演化和力学行为的影响,为高性能细晶Al-Mg(-Mn-Fe)合金的制备提供借鉴与参考。方法 采用连续流变挤压方法制备Al-Mg(-Mn-Fe)合金,对流变挤压态Al-Mg(-Mn-Fe)合金进行多道次累积连续流变挤压变形,研究多道次变形前后Al-Mg(-Mn-Fe)合金的微观组织和力学性能变化,讨论变形过程中Al6(Mn,Fe)相对动态再结晶的影响,揭示累积连续流变挤压态Al-Mg(-Mn-Fe)合金的强化机制。结果 经3道次累积连续流变挤压变形后,Al-Mg合金和Al-Mg-Mn-Fe合金的平均晶粒尺寸分别减小至21.5 μm和2.8 μm,细化效果显著;在多道次变形过程中,Al-Mg-Mn-Fe合金内的Al6(Mn,Fe)相逐渐破碎细化并趋于均匀分布,再结晶驱动力增加,阻碍再结晶晶粒长大;经3道次变形后,Al-Mg合金杆材的抗拉强度和伸长率同步提高至267.4 MPa和52.2%,而Al-Mg-Mn-Fe合金杆材的抗拉强度提高至364.2 MPa,伸长率降低至31.7%,该合金的强化机制主要包括细晶强化、位错强化和第二相强化。结论 累积连续流变挤压变形可有效细化合金内的晶粒及第二相,提高Al-Mg(-Mn-Fe)合金的综合力学性能。     

挤压Zn-Cu-Ti合金的组织及其力学性能

采用Zn-Ti中间合金等制备了不同铜含量的锌合金,370℃/4h均匀化后在300℃对合金进行了热挤压加工。通过X射线衍射分析、扫描电镜分析和能谱分析以及力学性能测试,研究了合金的微观组织和力学性能之间的关系。结果表明,Zn-Cu-Ti合金主要由锌的固溶体η相,TiZn15相和CuZn4相组成,Ti元素的加入细化了合金的显微组织,提高了合金的力学性能;热挤压过程中,合金发生动态再结晶和局部再结晶晶粒长大现象,TiZn15相和CuZn4相被破碎后沿挤压方向分布于晶界处,有助于阻碍再结晶晶粒的长大;Cu含量在0.5%~3.0%范围内,随着含铜量的增加,Zn-Cu-Ti合金的强度和硬度增大,当Cu含量超过2.0%时伸长率有下降趋势;由于挤压过程中发生了动态再结晶在一定程度上抵消了加工引起的硬化,合金挤压态硬度较铸态硬度提高不大。     

Sn-58Bi-(0~3)Ga/Cu润湿剪切性能及界面化合物的研究

采用熔炼铸造法制备了Sn-58Bi-(0~3)Ga焊料合金,研究了Ga元素含量对合金熔化特性、润湿和剪切性能的影响,并利用扫描电镜研究了Sn-58Bi-(0~3)Ga/Cu基体界面特征。结果表明,Ga元素的添加降低了合金的熔点,增大了合金的熔程,相比于Sn-58Bi合金,Sn-58Bi-1Ga焊料合金在铜基体的铺展率显著下降,剪切强度略有提高,随着Ga含量提高至2%、3%,合金的铺展率略有下降,剪切强度显著降低;Sn-58Bi/Cu界面主要组成元素为Sn和Cu,Sn-58Bi-(1~3)Ga/Cu界面上出现了明显的Ga和Cu元素偏聚界面层,结合特征点的能谱成分分析,确定了界面化合物的组成。     

Sb,Bi 元素对 Sn-22 Sb 高温钎料合金组织的影响

目的研究Sb和Bi元素对Sn-22Sb钎料显微组织的影响。方法制备了(Sn-22Sb)-xBi和Sn-xSb钎料合金,并分别采用差热分析和X射线衍射仪,分析了材料的熔化特征和物相。结果结果表明:Sn-22Sb钎料合金主要由灰色的β-Sn和白色块状的Sb2Sn3构成;少量的Bi使得Sn-22Sb钎料合金中Sb2Sn3金属间化合物逐渐细化和均匀化,数量却急剧增加;大量添加Sb后,使得Sn-22Sb钎料合金几乎全部变为粗大的块状β-SnSb组织,钎料合金的开始熔化温度有所提高。结论通过添加其他合金元素,降低Sn-50Sb钎料液相线温度,使其有望应用于二次回流焊。     

半固态组织对Sn-52Bi合金塑性与熔化潜热的影响

在150℃下对半固态亚共晶Sn-52Bi浆料分别进行5,10和15 min的机械搅拌,采用真空吸铸水冷制备出半固态Sn-Bi合金,测试了半固态Sn-Bi合金的组织、力学与热性能,研究剪切力对半固态浆料组织演变的影响,探索半固态合金延伸率与熔化潜热的关系。结果表明:对Sn-52Bi半固态浆料进行机械搅拌,剪切力可抑制树枝状初生Sn相的形成,真空吸铸水冷得到的合金组织由非树枝状的初生Sn相和共晶体构成;随着搅拌时间的延长,短锤状初生Sn相转变为直径约20μm的近球状,搅拌时间延长至15 min时球状初生Sn相直径变小但出现团聚。当搅拌速度为320 r/min,机械搅拌时间为10 min工艺得到半固态Sn-Bi合金延伸率为46.75%,与180℃下的合金熔液直接水冷凝固相比提高了160%;差式扫描量热分析(DSC)得出:不同机械搅拌时间半固态Sn-52Bi合金的峰值温度为140℃,随着合金延伸率升高,合金的熔化潜热减小。     

FGH96合金热挤压棒材超塑性研究

对热挤压FGH96合金棒材超塑性进行了研究,结果表明:挤压FGH96合金在1050℃和1100℃的变形温度下具有良好的超塑性,在变形温度为1100℃初始应变速率为3.33×10-4s-1进行超塑拉伸时,伸长率可以达到405%,流变应力降低到32MPa。显微组织分析表明,FGH96合金经控制冷却速度的预热处理后,合金中γ′相尺寸及间距较大,能够促进合金在后续变形过程动态再结晶的发生,并阻碍晶粒快速长大。FGH96合金在挤压变形后发生了明显的动态再结晶,但由于再结晶进行的不充分,晶粒内部仍存在大量变形亚结构,这种亚稳态组织在超塑变形过程中通过进一步回复和再结晶,可以获得平均晶粒尺寸为10μm左右的等轴、均匀、稳定的细晶组织,使合金具有良好的超塑性。     

挤压态AZ40镁合金热变形行为及热加工图分析

采用Gleeble-3500热模拟试验机对挤压态AZ40合金进行热压缩实验,分析压缩后不同温度真应力-应变曲线的变化趋势,得到流变应力受变形温度和应变速率等因素的影响规律;在双曲正弦关系的基础上构造挤压态AZ40合金的本构方程,在动态材料模型(DMM)基础上建立挤压态AZ40合金的热加工图,从而确定挤压态AZ40镁合金的热变形加工范围.结果表明:明显的动态再结晶是挤压态AZ40镁合金流变曲线的特点,在压缩过程中,随变形温度的升高,挤压态AZ40镁合金的峰值应力减小;随应变速率升高,挤压态AZ40镁合金的峰值应力增大.当变形温度相同时,动态再结晶晶粒比例随着应变速率的升高而降低;当应变速率相同时,动态再结晶晶粒大小随着变形温度的升高而增大.粗大的未再结晶晶粒有明显的<1010>‖ND和<21-1-0>‖ND两种取向,而再结晶晶粒取向随机;通过热加工图及组织分析,确定了最佳的加工工艺为T=573 K,ε·=0.1 s-1.     

TB17钛合金β相区动态再结晶行为及转变机理EI北大核心CSCD

通过Gleeble-3800热压缩模拟试验机对TB17钛合金β相区进行热压缩实验,研究该合金β相区的动态再结晶行为及转变机理。结果表明:TB17钛合金在β相区变形时会发生动态回复(DRV)与动态再结晶(DRX)。不同应变速率下存在两种动态再结晶形核位置,低应变速率下主要在晶粒内部形核,高应变速率下主要在晶界附近形核。通过EBSD和TEM分析可知,在低应变速率下发生连续动态再结晶(CDRX),其发生的主要形式为亚晶合并转动。高应变速率下发生不连续动态再结晶(DDRX),发生的主要形式为晶界剪切伴随着亚晶转动。尽管两种动态再结晶的转变方式不同,其本质都是通过位错的增殖、滑移和胞状结构演化形成新的动态再结晶晶粒。     

NiAl超塑性变形的正电子寿命研究

研究了B2型多晶NiAl的晶界结构对缺陷态正电子寿命的影响，并结合正电子谱探讨了热挤压及超塑性变形过程后的晶界结构，热挤压的NiAl合金具有有完全的再结晶组织，而超塑性变形过程中的动态回复和再结晶是一种不完全再结晶过程，所得到的晶界仍属于亚晶界或小角度晶界范畴，再结晶晶界在超塑性变形过程中不产生滑动。     

Effects of tin particles addition on structural and mechanical properties of eutectic Sn–58Bi solder joint

Due to the inherent environmental and health toxicities associated with lead, the use of environmental friendly lead-free solder materials has become an unavoidable trend in the electronic packaging industry. Sn-58Bi alloy is gaining attention for its good material properties such as low melting point, reliability and high tensile strength. The presence of the bismuth-rich phase increases the brittleness of Sn-58Bi alloy. The purpose of this study is to suppress the brittleness of Sn-58Bi alloy by the addition of different wt% (0, 10, 20, 30) of Sn powder. The powder metallurgy method was used to prepare the samples. Scanning electron microscopy and energy-dispersive X-ray analysis were done to study the structural properties and a tensile test was done by a universal tensile machine to study the mechanical properties. The results reveal that the Sn particles partially dissolved in the Sn-58Bi solder matrix. The dissolution of Sn particles significantly improved the mechanical strength by 30%, suppressed the brittleness and improved the strain value by 1.3 times.

     

Zn-8%Al变形锌合金组织演化规律研究

通过对Zn-8%Al合金的熔铸、挤压和拉拔加工,采用金相显微镜、扫描电镜等分析手段,研究了该合金的组织演化和相转变规律。实验结果表明,铸锭凝固初期发生包晶反应L+α→β,初生晶α′边缘包围着一层更富Zn的η相,随着温度的不断下降,进而发生共晶反应L→η+β与共析反应β→η+α。在热挤压过程中,大变形量加工使得枝晶破碎,合金的微观组织得到明显细化,但在横截面上仍可以看到小的枝晶,包晶相β在挤压的过程中已经发生共析转变:β→α+η。由于挤压和拉拔过程中都产生大量的变形热,Zn为层错能高的金属,发生动态再结晶,但由于冷却速度很快,只能发生不完全动态再结晶。Zn在冷加工过程中,出现软化现象,除了可能发生动态回复与动态再结晶外,还有可能会发生η→ηm′+η′→η+α的相变。     

Mechanical response and structural development during the hot extrusion of a rapidly solidified Al-20Si-7.5Ni-3Cu-1Mg alloy powder

The consolidation of an air-atomized Al-20Si-7.5Ni-3Cu-1 Mg alloy powder was performed utilizing hot extrusion, to determine its extrudability and understand its structural development in relation to process parameters. One of the main features exhibited by the material in this process was a high degree of softening over a peak extrusion pressure, which has been explained by the simultaneous onset of dynamic recovery and recrystallization during deformation. The peak extrusion pressure was shown to be strongly dependent upon the temperature applied, and this dependence has been described with temperature compensated strain rate. It was also observed that the process parameters had a fairly narrow range applicable to the extrusion of the powdered alloy and a significant influence on the deformation behaviour of the powder particles. The combination of heating and deformation, primarily used to convert the loose powder particles into an engineering material, resulted in the decomposition of the meta-stable aluminium matrix and transformations of constituent phases, initially formed in the rapidly solidified powder. Additionally, it was found that the extrusion temperature had an effect on the lattice size and perfection of the as-extruded matrix in the material. Three intermetallic dispersoids containing nickel were detected in the consolidated material, independent of extrusion temperature, and their formation was promoted by hot deformation. The silicon crystal phase in the extruded material was reshaped, and its size was insensitive to the extrusion temperature, which is thought to be caused by a high volume fraction of the coexistent dispersoids. The dispersions of the silicon crystals and intermetallic compounds with various sizes in the matrix substantially modified the deformation mode of the alloy. Evidence of dynamic recrystallization was found, which co-operated with dynamic recovery during deformation, giving rise to a duplex microstructure in the extruded material.     

定向凝固Fe-6.5wt%Si合金热压缩变形行为研究

采用Gleeble 1500热模拟机对定向凝固Fe-6.5%(质量分数)Si合金进行热压缩变形研究。结果表明,Fe-6.5%(质量分数)Si合金柱状晶组织热形变过程中很难发生动态再结晶,以动态回复为主,易产生严重的变形带;在无序相区间,在柱状晶晶界处发生动态再结晶形核,但长大受到限制,仅局限于晶界附近。与锻态等轴晶组织相比,有序相区间,两种组织形变行为基本一致,受温度影响剧烈,在无序相区间,随温度升高,等轴晶组织的形变激活能略有升高,平均值约为294kJ/mol,而柱状晶组织的形变激活能逐渐降低,平均值约为260kJ/mol。     

GH4169合金变应变速率热变形过程动态再结晶动力学行为及建模

目的 研究变应变速率高温变形过程中GH4169合金动态再结晶行为和晶粒组织的演变机理.方法 在不同变应变速率工况下对GH4169合金进行高温压缩实验,分析了变形参数对动态再结晶行为与晶粒组织的影响规律,建立变应变速率工艺下GH4169动态再结晶动力学和晶粒尺寸预测模型.结果 随着第一阶段真应变的增加或第一阶段/第二阶段...     

5083铝合金的热变形组织演变及晶粒度模型

通过等温压缩实验、光学显微镜与透射电镜研究了变形温度300~450℃、应变速率0.01~1s-1、真应变0.36~1.2范围内变形条件对5083铝合金热变形组织演变的影响。结果表明:升高热变形温度或降低应变速率均可促进5083铝合金的动态再结晶发生,使变形后5083铝合金位错密度降低,再结晶晶粒尺寸增大;随着应变量的增加,变形后合金的位错密度降低,动态再结晶程度增大。根据唯象理论的指数模型,利用线性回归方法建立了5083铝合金动态再结晶晶粒度模型,模型计算值与实测值吻合良好,平均相对误差仅为4.6%。     

Forging property,processing map,and mesoscale microstructural evolution modeling of a Ti-17 alloy with a lamellar (α+β) starting microstructure

Abstract

This work identifies microstructural conversion mechanisms during hot deformation (at temperatures ranging from 750 °C to 1050 °C and strain rates ranging from 10^?3 s^?1 to 1 s^?1) of a Ti-5Al-2Sn-2Zr-4Mo-4Cr (Ti-17) alloy with a lamellar starting microstructure and establishes constitutive formulae for predicting the microstructural evolution using finite-element analysis. In the α phase, lamellae kinking is the dominant mode in the higher strain rate region and dynamic globularization frequently occurs at higher temperatures. In the β phase, continuous dynamic recrystallization is the dominant mode below the transition temperature, T_β (880~890 °C). Dynamic recovery tends to be more active at conditions of lower strain rates and higher temperatures. At temperatures above T_β, continuous dynamic recrystallization of the β phase frequently occurs, especially in the lower strain rate region. A set of constitutive equations modeling the microstructural evolution and processing map characteristic are established by optimizing the experimental data and were later implemented in the DEFORM-3D software package. There is a satisfactory agreement between the experimental and simulated results, indicating that the established series of constitutive models can be used to reliably predict the properties of a Ti-17 alloy after forging in the (α+β) region.     

Dynamic recrystallization behavior of AZ31 magnesium alloy processed by alternate forward extrusion

One of the important factors that affect the microstructure and properties of extruded products is recrystallization behavior. Alternate forward extrusion (AFE) is a new type of metal extrusion process with strong potential. In this paper, we carried out the AFE process experiments of as-cast AZ31 magnesium alloy and obtained extrusion bar whose microstructure and deformation mechanism were analyzed by means of optical microscopy, electron backscattered diffraction and transmission electron microscopy. The experimental results indicated that homogeneous fine-grained structure with mean grain size of 3.91 μm was obtained after AFE at 573 K. The dominant reason of grain refinement was considered the dynamic recrystallization (DRX) induced by strain localization and shear plastic deformation. In the 573-673 K range, the yield strength, tensile strength and elongation of the composite mechanical properties are reduced accordingly with the increase of the forming temperature. Shown as in relevant statistics, the proportion of the large-angle grain boundaries decreased significantly. The above results provide an important scientific basis of the scheme formulation and active control on microstructure and property for AZ31 magnesium alloy AFE process.