钕对Mg-5Al-1Si高温蠕变及组织性能的影响

研究了不同Nd含量对Mg-5Al-1Si镁合金的高温蠕变性能影响, 对析出相进行了分析, 研究了微观组织与力学性能的关系. 研究结果表明, 该合金中的主要强化相Mg2Si呈粗大的汉字状, 分布在晶界的周围, 在受到应力时, 这种汉字状相与基体的界面处易产生微裂纹, 降低合金的抗拉强度、塑性等力学性能. 在Mg-5Al-1Si合金中加入微量的Nd以后, 合金的组织得到明显的细化, 并使Mg2Si强化相形貌由粗大的汉字状转变为细小、弥散分布的颗粒状. 由于显微组织的改善, 使得Mg-5Al-1Si镁合金的室温和高温力学性能均有一定的提高, 并明显的改善了Mg-5Al-1Si的抗蠕变性能.     

含钪Al-Zn-Mg-Cu-Zr合金组织性能的研究

采用金相显微镜、扫描电子显微镜和透射电子显微镜研究了微量钪对Al-Zn-Mg-Cu-Zr系合金组织的影响，测试了不同热处理状态下台金的力学性能和电导率。结果表明，添加微量Sc可以明显细化合金的铸态晶粒，显著提高Al-Zn-Mg-Cu-Zr合金的力学性能和电导率，其作用机制主要为AJ3（Sc，Zr）引起的细晶强化、亚结构强化和沉淀强化；Al-9．0Zn-2．5Mg-1．2Cu-0．15Zr-0．12Sc和Al-9．5Zn-2．5Mg-1．2Cu-0．15Zr-0．12Sc经强化固溶和T6处理后，抗拉强度分别达到829．4和818．6MPa。     

镧对Mg-Si合金中Mg2Si相变质的影响

研究了Mg-5Si合金中La的添加对初生Mg2Si相变质的影响。结果表明,适量的La能够有效地变质初生Mg2Si相。基于本文的研究,在添加约0.5%La时,获得了最佳的变质效果,此时,初生Mg2Si相的尺寸减小到25μm以下,其形态从粗大的树枝形状变为多面体形状。然而,当La增加到0.8%或者更高时,初生Mg2Si相又生长为粗大的树枝形态。而且,在凝固过程中发现形成了一些LaSi2化合物,这些化合物的数量随着La的增加而呈现逐渐增加的趋势。     

Mg-SiO_2体系制备Mg_2Si/AZ91D复合材料的研究

采用原位合成技术制备了Mg2Si/AZ91D复合材料,并通过光学显微镜(OM)、扫描电镜(SEM)、能谱仪(EDS)和X射线衍射仪(XRD)等对添加碱土、稀土元素的影响进行了研究。结果表明:AZ91D镁合金中加入SiO2(其中Si占合金质量的3%)后,出现多边形状或树枝晶状的初生Mg2Si相,以及汉字状的共晶Mg2Si相,树枝晶状Mg2Si的平均尺寸约25~50μm,汉字状Mg2Si的平均尺寸约12~15μm;Mg2Si对镁合金中的β-Mg17Al12相有细化作用。添加Ca,Sr,Y对Mg2Si形貌、尺寸有明显的改善,当添加0.9%Ca,0.1%Sr,0.5%RE(80%Y)变质处理后,Mg2Si形貌全部变为多边形状,平均尺寸约0.8~5μm。     

Mg-13Gd-2Nd-2Cu合金的显微组织与力学性能

通过熔炼铸造及热挤压方法制备了Mg-13Gd-2Nd-2Cu(质量分数)镁合金。通过金相显微镜、扫描电镜及能谱分析、维氏硬度、拉伸性能测试等方法,研究了Mg-13Gd-2Nd-2Cu合金的铸态显微组织特征及退火温度对挤压态合金的组织与力学性能影响。结果表明:退火热处理促进了晶界处Mg5(GdNdCu)_1相充分溶入α-Mg基体中。提高退火温度使基体晶粒发生再结晶长大,改变了Mg5(GdNdCu)_1相的形态和分布。当退火温度超过500℃时,晶粒粗化并部分发生过烧现象。提高退火温度,会使挤压态合金的屈服强度有所降低。     

Al-5Mg-Er合金中Al3Er相的析出及其热力学计算分析

通过应用Miedema热力学模型方法对添加了微量Er的Al-5Mg合金中的Er的存在形式进行了初步的分析，并结合XRD，TEM试验进行了验证。微量Er在Al-5Mg合金中主要是以Al3Er的形式存在，并且不会出现元素Mg与Er之间的金属间化合物；同时通过XRD和TEM分析证实，含微量Er（0．1％～0．7％）的Al-5Mg合金中Er是以Al3Er相存在并且弥散分布，讨论了Al3Er相与Al基体之间的取向关系，分析了Al3Er相的存在能够改善Al-5Mg合金材料的机械性能。     

钇对AZ61镁合金组织和性能的影响

在CO2+SF6气体保护条件下感应熔炼制备了不同Y含量的AZ61-x Y(x=0,0.5,1,1.5,2)镁合金,利用光学金相显微镜(OM)、扫描电镜(SEM)、X射线衍射分析(XRD)、能谱分析(EDS)和拉伸及蠕变力学性能测试手段研究了Y添加对AZ61合金显微组织和力学性能的影响。结果表明:合金中添加适量的稀土元素Y后,AZ61合金的显微组织得到明显的细化,合金中除了存在α-Mg和Mg17Al12相,还出现了块状析出相Al2Y。适量的Y显著提高了合金在室温和高温时的强度和塑性,同时合金在150℃/70MPa条件下的抗蠕变性能也有显著的提升。     

钕对Mg7Zn2Al镁合金显微组织及力学性能的影响

采用光学显微镜、XRD、SEM和万能实验机等手段研究了稀土Nd(0.3%,0.6%,0.9%)对Mg7Zn2Al镁合金显微组织和力学性能的影响。结果表明:Mg7Zn2Al镁合金中添加Nd后,显微组织中有针状或棒状的Al2Nd和AlNd等稀土相生成,合金中的共晶组织(α-Mg+Mg32(Al,Zn)49+Mg7Zn3)得到了明显细化;但是α-Mg有粗化趋势,呈现发达的树枝状或胞状,共晶相由粗大连续的网状变为细小的块状或颗粒状分布在树枝晶的一次枝晶臂或二次枝晶臂的间隙。随着Nd含量的增加,合金的抗拉强度和延伸率呈逐渐下降趋势,显微组织的粗化是造成合金拉伸性能降低的主要原因,而硬度没有明显的变化。     

高钆耐热镁合金在高温蠕变过程中的显微组织演变

以时效态Mg-12Gd-3Y-1Sm-0.5Zr (%,质量分数)合金为研究对象,利用蠕变持久试验机在250℃/50 MPa下对合金的蠕变性能进行了测试,并采用TEM研究了合金在250℃/50 MPa下蠕变10, 30 min, 100 h过程中的显微组织和相的演变。结果表明:时效态Mg-12Gd-3Y-1Sm-0.5Zr合金相由α-Mg基体和β′相组成,β′相为纳米析出相,在高温蠕变过程中,晶内析出相明显长大,形貌由黑色椭圆形颗粒向菱形和长条状转变,经对应的选区电子衍射谱标定,相结构未发生变化;晶界上析出相粗化,转化为平衡相β相。本研究为开发高温高强抗蠕变耐热镁合金提供理论基础。     

锌对稀土镁合金组织与力学性能的影响

采用OM, XRD, SEM和EDS等试验手段研究了Zn对稀土镁合金Mg-4Y-1Ca(%,质量分数)微观组织和力学性能的影响。结果表明:随着Zn (x=1%, 3%, 5%)的加入, Mg-4Y-1Ca合金中生成的Mg_(24)Y_5二元相逐步转变为Mg_3Y_2Zn_3(W相)+Mg_(12)YZn(X相)三元相,铸态组织细化,第二相沿晶界成网状分布;经热挤压变形后,合金再结晶后晶粒细化明显,第二相弥散分布于基体和晶界上,强度提高的同时伸长率也获得较大提升,其中Mg-4Y-1Ca-5Zn合金表现最为显著。得益于Zn添加对再结晶晶粒细化和W相、 X相弥散强化的共同作用, Mg-4Y-1Ca-5Zn合金经热挤压处理后具有较佳的综合力学性能,屈服强度、抗拉强度和伸长率分别达到198 MPa, 271 MPa和24.6%。     

Microstructural and Mechanical Properties of Al-20%Si Containing Cerium

In this paper the effect of cerium addition in hypereutectic Al-Si alloys was studied. Casting method was used to produce Al-20Si with variation of Ce contents. The sample characterization studied was investigated by Optical Microscope, X-ray fluorescence and X-ray Diffraction. Vickers microhardness and wear test was carried out to study the influence of Ce towards the Al-20Si alloys. The addition of Ce in the Al-20Si alloys refined the Si primary phase as the Ce content increases. The results showed that the addition of 0.46 to 2.24 wt.% of cerium in Al-20Si alloys led to the formation of fine cells dispersed in the Al-matrix. These fine cells consist of a mixture of eutectic Si particles and intermetallic Al3Ce and CeAl1.2Si0.8 phase in Al matrix. The amount of rod- like intermetallic Al3Ce and CeAl1.2Si0.8 phase increases with increasing Ce content. The microhardness of Al-20Si alloys increases with the increase in Ce content. Addition of Ce up to 1.61 wt.% Ce improve the wear properties of Al-20Si alloy.     

Effects of Ca and Ag addition and heat treatment on the corrosion behavior of Mg-7Sn alloys in 3.5 wt.% NaCl solution

The effects of 1 wt.% Ca or 1 wt.% Ca + 1 wt.% Ag addition and heat treatment on the corrosion behavior of Mg-7Sn (wt.%) alloy in 3.5 wt.% NaCl solution were investigated by electrochemical measurements and immersion tests. The alloys were characterized by optical microscope (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). It was found that all alloys were corroded by pitting corrosion and grain boundary corrosion and further corroded with time going. Loose layers of compounds, including Mg (OH)₂, MgO, SnO₂, and other compounds containing Ca and Ag elements, were calibrated on the surface of corroded Mg-7Sn-1Ca-1Ag alloy. The Ca addition improved the corrosion resistance of Mg-7Sn alloy due to the formation of relatively stable compounds containing calcium element and grains refinement. Furthermore, the solid solutioned alloys obtained a superior corrosion resistance due to the dissolve of eutectic Mg₂Sn phase and homogenization treatment. However, the aging treatment is slightly detrimental to the corrosion resistance of Mg-7Sn alloys with the formation of Mg₂Sn precipitates. In conclusion, the aged Mg-7Sn-1Ca-1Ag alloy exhibited a better corrosion resistance and a noticeable micro-hardness property compared with those of as-cast Mg-7Sn alloy. And this study provides an important idea for the research on the comprehensive properties of Mg-Sn alloys.     

A Study of Precipitates Formation in AA 380.0 Aluminium Alloys Modified by the Addition of Magnesium

A data acquisition system and the SAD2 software, that provide characteristic cooling curves, in combination with microstructure analysis were used to study precipitates formation in the AA380.0 aluminium alloys modified by adding extra magnesium. The samples were solidified with distinct cooling rates caused by carrying out the solidification in shell and permanent molds. The mathematics processing of the cooling curves in agreement with the microstructure analysis have confirmed the remarkable presence of both the Al–Si dendrite network and the Mg2Si interdendritic phase in the alloys with the addition of extra magnesium. This revised version was published online in July 2006 with corrections to the Cover Date.     

富钇混合稀土对AM60镁合金显微组织与力学性能的影响

在AM60镁合金的基础上添加不同质量分数的富Y混合稀土(分别为0.5%,1.0%,1.5%,2.0%),研究了富钇混合稀土对AM60镁合金显微组织与力学性能的影响。结果表明:富Y稀土的加入使AM60镁合金的显微组织明显细化,并能显著提高合金的抗拉强度、屈服强度及延伸率。加入混合稀土后,合金中形成块状的铝钇化合物Al2Y,Al6Mn6Y,β-Mg17Al12相数量减少。当稀土加入量为1%时,合金的各方面性能达到最好。     

The effects of a eutectic modifier on microstructure and surface corrosion behavior of Al-Si hypoeutectic alloys

Hypoeutectic aluminum–silicon alloys can have significant improvements in mechanical properties by inducing structural modification in the normally occurring eutectic. The eutectic modification may affect not only the mechanical properties but also the corrosion resistance of such alloys. It is well known that structural parameters such as grain size and interdendritic spacing can significantly affect corrosion resistance of alloys. However, to date, few researches have been performed to experimentally evaluate the effects of an effective modification of eutectic morphology on surface corrosion behavior of Al–Si alloys. In the present study, modified and unmodified samples of an Al 9 wt.% Si alloy were solidified under similar solidification conditions, and after metallographic procedures, the corrosion resistance was analyzed by both the electrochemical impedance spectroscopy technique and the Tafel extrapolation method carried out in a 0.5 M NaCl test solution at 25 °C. The impedance parameters and corrosion rate were obtained from an equivalent circuit analysis. It was found that the Al-9 wt.% Si alloy casting in the modified condition tends to have its corrosion resistance decreased when compared to the unmodified alloy.     

四元Mg0.9Ti0.1Ni0.9X0.1(X=Mn,Zn,Co,Fe)系列合金的制备及性能研究

用机械合金化法合成了Mg0·9Ti0·1Ni0·9X0·1(X=Mn,Zn,Co,Fe)系列合金.X射线衍射(XRD)结构分析表明,用X部分替代Ni后,促进了Mg0·9Ti0·1Ni合金的非晶化过程.用Co和Fe部分替代Ni提高了合金的放电容量,但却降低了合金的循环稳定性.用Zn和Mn部分替代Ni提高了合金电极的循环寿命,尤其是Mg0·9Ti0·1Ni0·9Zn0·1合金电极经10个充放电循环后,其放电容量仍可达到313·8mA·h/g.对添加Co后的合金进行p-c-T测试发现,Mg0·9Ti0·1Ni0·9Co0·1合金的吸放氢容量明显比Mg0·9Ti0·1Ni合金高,这与电化学所测到的结果一致.     

TEM and SNMS studies on the oxidation behaviour of NiCrAlY-based coatings

The effect of minor Ti additions content (0% Ti, 0.4% Ti, 1% Ti, 2% Ti) on the oxidation behaviour of Ni-20Cr-10Al-0.4Y (in weight-%) model alloys was investigated in the temperature range 950° C to 1100° C up to 200 h in Ar – 20% O₂. Alloy microstructure, oxide scale morphology and microstructure of the scale were characterized by SEM/EDX and TEM. The growth mechanisms of the alumina scales formed on the model alloys were studied by two-stage oxidation experiments with ¹⁸O₂-tracer and subsequent SNMS-analyses. The microstructural observations were correlated with the oxide scale properties in respect to growth rates and spalling resistance, which was tested during cyclic oxidation. Received: 24 June 1996 / Accepted: 18 November 1996