磷元素对Al-Mg2Si合金显微组织的影响

研究了P元素的加入对Al-Mg2Si合金组织的影响.结果表明在常规铸造条件下,Al-Mg2Si合金中初晶Mg2Si为粗大的多角形块状.经过P元素变质后合金中的初晶Mg2Si得到明显细化,并成为分布较均匀的块状或球团状,当加入的P元素量为0.5%时,初晶Mg2Si最细小、圆整.其实质是P元素与Mg元素形成的Mg3(PO4)2化合物充当了Mg2Si的形核核心.     

离心铸造Al-24％Si合金自生梯度复合材料

摘要本文通过改变离心铸造的转速,获得了初晶Si由外向内或由内向外富集的Al-24wt%Si合金自生梯度复合材料。分析了复合材料的形成过程,考察了复合材料的组织、硬度和初晶si的分布。     

Mn对Al-Si合金中Fe相形态的影响

在含Fe的Al-Si合金中加入Mn元素，铸成试样和焊丝，研究了Mn对铸态金属和氩弧熔敷金属中Fe相形态的影响，发现在铸态只生成一种多边形汉字状的Al-Fe-Si相，在焊态熔敷金属中生成多种形态的Al-Fe-Mn-Si相，有多边形汉字状（块状），六角星状，鱼骨状和小花状，Mn对铸造Al-Si合金和焊态Al-Si合金中的针状Fe相均有很好的抑制作用，X射线衍射发现，熔敷金属中存在A19Fe0.84Mn2.16Si,A10.7Fe3Si0.3,Mn12SiA15相及其它一元，二元相。     

Al-27Zn合金固溶时效后硬度及耐磨性研究

研究了两种Al-27Zn合金经425℃×8h固溶及125℃时效处理后组织结构、硬度和耐磨性的变化规律.结果表明,经时效处理后合金的组织形态为：Al基体上均匀分布着少量未溶树枝状晶组织以及大量细小弥散富锌的η相;合金的硬度随着时效时间的延长先升后降,合金元素Cu、Mg的加入提高了Al-27Zn的硬度;两种合金均具有良好的耐磨性,但合金元素Cu、Mg的加入降低了耐磨性;探讨了磨损机制及材料组织、硬度对合金耐磨性的影响.     

Al—27Zn合金固溶时效后硬度及耐磨性研究

研究了两种Ａｌ－２７Ｚｎ合金经４２５℃ ｘ ８ｈ固溶及１２５℃时效处理后组织结构、硬度 和耐磨性的变化规律．结果表明．经时效处理后合金的组织形态为：Ａｌ基体上均匀分布着 少量未溶树枝状晶组织以及大量细小弥散富锌的η相；合金的硬度随着时效时间的延长先 升后降，合金元素Ｃｕ、Ｍｇ的加入提高Ａｌ－２７Ｚｎ的硬度；两种合金均具有良好的耐磨 性，但合金元素Ｃｕ、Ｍｇ的加入降低了耐磨性；探讨了磨损机制及材料组织、硬度对合金 耐磨性的影响．     

δ-Al2O3短纤维增强Al合金复合材料热残余应力及其影响

用弹塑性有限元法和双纤维模型研究了δ-Al2O3，短纤维增强Al合金复合材料在室温下的热残余应力的分布及其对复合材料整体力学性能的影响．计算了体积分数为20％的3种δ-Al2O3／A1合金复合材料的拉伸应力-应变关系，并与实验结果比较．纤维间相互作用使复合材料基体中的热残余应力的大小发生了变化，但对其空间分布规律没有影响．对于体积分数为20％的短纤维增强δ-Al2O3／Al-5．5Mg和δ-Al2O3／Al-5．5Zn复合材料，用双纤维模型的三维弹塑性有限元方法计算的应力-应变曲线与实验曲线符合得较好，但δ-Al2O3／Al-12 Si复合材料的模拟结果与实验结果相比误差较大．     

过共晶铝硅合金变质工艺研究

本文研究了P、RE、S单独加入及P-RE、P-S、P-Na联合加入对Al-20％Si合金的变质作用，比较了各自的变质效果。考察了联合变质的最佳变质温度及联合变质长效性。结果表明，P-RE、P-S联合变质具有较好的双重变质效果，联合变质后合金机械性能有较大的提高。最佳变质温度为840℃左右，变质效果至少可持续3h.     

Si/C比变化对高碳当量灰铸铁组织性能的影响

研究了Si／C比对含V、Ti高碳当量(4．10％～4．25％)灰铸铁组织性能的影响．结果表明，随Si／C比提高，铸铁显微组织中珠光体和D、E型石墨逐渐减少Si／C比从0．38～0．45提高到0．60～0．76，可以使铸铁抗拉强度提高9～26MPa，硬度提高0～13HB；合适的Si／C比是在0．60～0．76范围内。     

Cr—Mo合金片状石墨铸铁氧化膜构造的研究

本文应用金相显微镜、扫描电镜,X-射线衍射仪研究了在900℃,latm 条件下片状石墨铸铁(3.59%C,2.5%Si,0.22%Cr,0.20%Mo)的氧化膜以及内部氧化区的结构,结果表明:氧化膜大致分为两层:外层是由纯铁的氧化物组成,内层是由铁的氧化物与 Si,Cr 合金元素的氧化物组成.外层又可分为三层,山外向内依次是 Fe_2O_3,Fe_3O_4,Feo,外层的生长机理与纯铁的氧化相同.内层与内部氧化区又存在特殊的氧化区域.这个特殊的氧化区是由于石墨与 O_2的直接作用,产生气体向外逸出,留下的空腔被金属氧化产物充填而产生的.合金元素Si,Cr 在该区的富集并不是山于合金元素在石墨片周围的偏析,而是由于 O_2沿石墨片与基体的缝隙侵入,石墨片边缘的合金元素被优先氧化的缘故.     

La和Sr对AlSi9Cu1Mg合金变质效果 的热分析研究

研究了La与Sr复合变质对AlSi9Cu1Mg合金变质效果及冷却曲线特征的影响。研究结果表明:La与Sr对AlSi9Cu1Mg合金变质有协同作用,加入0.1%La与0.02%Sr可将共晶硅转变为点状和蠕虫状;La和Sr变质使得AlSi9Cu1Mg合金共晶硅生长最低温度和最高温度降低、共晶再辉温度增加,共晶再辉温度越大,共晶硅的变质效果越好,达到2.8℃时,可获得正常变质组织;共晶再辉温度值可以作为评价AlSi9Cu1Mg合金变质效果的判据。     

磷—钠联合变质对过共晶铝硅合金组织的影响

用磷铜合金和四元钠盐变质剂对过共晶铝硅合金进行了变质处理试验。结果表明:磷一钠联合变质,能使初晶硅和共晶硅同时细化,但变质效果不甚稳定。     

Fe-30Mn-2．7Si合金单宁酸化学转化膜研究

以优选工艺,进行单宁酸溶液处理Fe-30Mn-2.7S i恒弹性合金,在其表面形成化学转化膜.采用X射线衍射与扫描电镜及在1 mol/L Na2SO4溶液中测定阳极极化曲线与电化学阻抗谱等技术研究化学转化膜的结构、成膜机制与提高其耐电化学腐蚀性能的效果.依据在Fe-30Mn-2.7S i合金表面进行10%CuSO2滴浸的加速腐蚀实验,初步选定较优的单宁酸反应成膜工艺条件.这种转化膜很可能是由有一定孔隙的非晶态合金单宁酸膜层构成.在1 mol/L Na2SO4溶液中,由阳极极化曲线与电化学阻抗谱等参数表征单宁酸转化膜的抗腐蚀性能优于Fe-30Mn-2.7S i合金基体.文中还简要地讨论单宁酸转化膜的结构与电化学性能.     

Microstructure and hardness of Ni-xSi alloys

The microstructure and hardness of conventionally solidified Ni-xSi (x = 21.4%, 22%, 24%, 26%) alloys were investigated. The solidification microstructures of different Ni-Si alloys were observed by optical microscope (OM) and scanning electron microscope (SEM) and the phase composition was indentified under the help of energy dispersive X-ray (EDX) analysis. The macro- and micro-hardness of the Ni-Si alloys at room temperature were also examined. The experimental results indicated that both the microstructure and hardness closely depended on the Si content. Due to the vast formation of primary ??-Ni₃₁Si₁₂ phase, the hardness of Ni-26.0%Si alloy was significantly improved compared with that of Ni-21.4%Si eutectic alloy. However, the fracture toughness was greatly weakened simultaneously. The (?? ₁-Ni₃Si+??-Ni₃₁Si₁₂) lamellar eutectoid structure formed in the primary ??-Ni₃₁Si₁₂ phase exhibited better ductility than single ??-Ni₃₁Si₁₂ phase at the cost of relatively small hardness reduction.     

Precision Improvement of the Discrete Calculation Method for Sound Radiation Research

Sound radiation of thin plates is a common problem in engineering. Hashimoto proposed the discrete calculation method(DCM) to deal with the problem. The calculation of the radiation impedance of the rectangular element is more cumbersome than that of the circular one, so the discrete rectangular radiation element is approximated by the circular one. However, error is also introduced. The formula developed by Sha has been employed to get self- and mutual-radiation impedances of rectangular radiation element. Numerical study was performed to verify error introduced by the approximation Hashimoto adopted. Experimental researches on sound radiation of a 2 mm-thick and a 4 mm-thick magnesium alloy plates were also carried out to evaluate the errors introduced by the approximation. The experimental results indicate that the circular approximation Hashimoto adopted overestimates the sound radiation efficiency. The maximum error levels of the radiation efficiencies of the2 mm-thick and 4 mm-thick magnesium alloy plates are up to 0.15 and 0.12, respectively. The effect of element aspect ratio on the sound radiation efficiency is also remarkable.     

EFFECT OF La-RICH RE ON THE STRUCTURE AND PROPERTIES OF B319 ALLOY IN LOST FOAM CASTING

IntroductionLost foam casting( LFC) process is a newtechnology that is different from the conventionalempty mould cavity casting completely.This tech-nology is an important orientation of casting tech-nology,and is called as casting technology for to-morrow.At present,the studies on LFC are fo-cused on casting techniques mainly[1～ 5] .There islittle information on the structure and mechanicalproperties of B31 9in LFC process.Now for alu-minum alloy in LFC process,the main problemsare se…     

Investigation of the capabilities of yield functions on describing the deformation behavior of 5754O aluminum alloy sheet under combined loading paths

The combined loading tests of 5754O aluminum alloy sheet are used to verify the yield function. Three yield functions are implemented into the commercial finite element model (FEM) code ABAQUS as a user material subroutine UMAT for the FEM simulation of the combined loading tests. The comparison of the simulating and experimental results shows that the modified Yld2000-2d yield function can describe the mechanical behavior of 5754O aluminum alloy sheet under combined loading paths reasonably while other three yield functions do not. The performance of the modified Yld2000-2d yield function on describing the mechanical behavior under combined loading paths is analyzed in detail. It is concluded that the modified Yld2000-2d yield function can be adopted to describe the deformation behavior of 5754O aluminum alloy sheet for industrial applications.     

Effect of remelting current on molten pool profile of titanium alloy ingot during vacuum arc remelting process

The performance of vacuum arc remelting (VAR) ingot depends largely on ingot structure and chemical uniformity, which are strongly influenced by molten pool profile that is influenced by VAR process. To better understand the effect of remelting current on molten pool profile of titanium alloy ingot during VAR process, a 3D finite element model is developed by the ANSYS software. The results show that there are three remelting stages during VAR process when the remelting current is 2.0 kA. The molten pool depth increases gradually from 30 to 320 s, then the change of molten pool depth is very small during the steady state stage from 320 to 386 s, and lastly the molten pool depth becomes shallow after 386 s. The melting rate and temperature of superheat increase with the remelting current increasing, which leads to the augment of molten pool volume. In the end, the total remelting time and steady state molten pool time decrease with the melting current from 1.6 to 2.8 kA.     

TGF-β_2对体外培养的牛眼小梁细胞MMP_2表达和活性的影响

目的了解转化生长因子-β2(TGF-β2)对体外培养的牛眼小梁(TM)细胞基质金属蛋白酶-2(MMP2)的表达和活性的影响,探讨TGF-β2在原发性开角型青光眼(POAG)发病机制中的作用。方法用含有1.0μg/L TGF-β2或含1.0μg/L TGF-β2+100g/L鼠抗人PAI-1IgG(PAI-1中和抗体)的无血清DMEM分别孵育TM细胞24、36、48h。对照组(Co)加入不含实验药物的无血清DMEM,用Western印迹法检测MMP2及纤溶酶原活化抑制剂-1(PAI-1)的表达。结果TGF-β2可显著增强TM细胞MMP2前体及PAI-1的表达。PAI-1中和抗体可促进MMP2前体向其活化形式转化。结论TGF-β2可通过抑制MMP2的活化过程导致TM细胞的细胞外基质(ECM)的异常堆积,造成房水引流阻力的增加,参与POAG的发病。     

Si—Mo铸铁耐热性能的研究

Si-Mo 合金耐热铸铁作为一种玻璃模具材料,除其他各种性能之外,还特别要求应具有较好的耐热性能,以保证模具在高温下能稳定工作.本文通过对 Si-Mo 铸铁高温氧化、生长的实验,系统分析了 Si-Mo 铸铁的高温氧化、生长特性及合金元素、石-墨形态、蠕化率的影响.同时,对合金元素在铸铁中的分布进行了波谱扫描分析.结果表明:Si-Mo 铸铁具有良好的高温抗氧化和抗生长性能;Si,Mo,石墨形态及蠕化率都能显著地影响其耐热性能;合金元素在氧化膜中都有不同程度的偏聚.因此,本研究为 Si-Mo铸铁在玻璃模具上的应用提出了一定的理论及实验依据.