Mg-6Al-2Sr-xNd镁合金的显微组织和力学性能

研究了Mg-6Al-2Sr-xNd镁合金的显微组织和常温力学性能,探讨了合金中Nd与Sr复合添加后的存在形式及不同含量的Nd对合金常温力学性能的影响.结果表明：Al4Sr相呈网状沿晶界分布,而Al11Nd3相呈颗粒状或针状,在晶内、晶界均有析出.Al4Sr相在晶界起到了阻止晶界滑移的作用,Al11Nd3相在晶内有钉扎位错的作用,晶界晶内的双重强化提高了合金的强度.合金的抗拉强度、屈服强度和伸长率均在含Nd量为1.0%时达到了峰值.     

微量Ca对Mg-6Al-1Y-1Nd合金组织和性能的影响

利用感应熔炼制备了不同Ca含量的Mg-6Al-1Y-1Nd-xCa(x=0、0.1、0.4、0.7)镁合金,采用光学金相显微镜、扫描电镜、X射线衍射分析、能谱分析和拉伸及蠕变力学性能等手段研究了微量Ca元素添加对Mg-6Al-1Y-1Nd镁合金显微组织和力学性能的影响。研究结果证实,添加微量的碱土元素Ca使得Mg-6Al-1Y-1Nd镁合金的显微组织明显得到细化,Mg-6Al-1Y-1Nd合金主要存在Al_2Y和Al_2Nd块状稀土析出相,Ca元素的添加使得该合金形成了呈条状和骨骼状的新析出相Al_2Ca。力学性能测试结果证实微量Ca元素添加能够显著提高Mg-6Al-1Y-1Nd镁合金在室温和高温条件下的强度和塑性,同时显著提升了该合金在150～200℃/70 MPa测试条件下的抗蠕变性能,表明Ca是Mg-6Al-1Y-1Nd镁合金重要强化添加元素。     

Mg-6Al-(Sr,Ca)合金的显微组织和蠕变性能

系统研究了Mg-6Al—2Sr和Mg-6Al-（1—2）Sr-1Ca合金在水冷模铸造和压铸态下的显微组织、力学及蠕变性能．Mg—6Al-2Sr合金的铸态组织由α-Mg和沿枝晶界分布呈片状的α—Mg＋Al4Sr共晶相组成．在Mg-6Al-2Sr基础上加入少量的Ca，合金中的Al4Sr被Mg2Ca取代，且出现了Mg-Al—Sr三元中间相，合金的抗蠕变性能显著提高．对蠕变后试样进行的扫描电镜观察表明。Mg-6Al合金中添加Sr和Ca后形成的中间相均具有很高的热稳定性．Mg-6Al—2Sr合金蠕变后的试样中出现了β-Mg1τTAl12相的非连续析出；而采用Sr和Ca复合合金化的试样显微组织在蠕变后无明显变化，也未析出卢相，因而显著地提高了合金的抗蠕变性能．与水冷模铸造试样相比，压铸试样具有更细的显微组织和更高的室温与高温力学性能。但抗蠕变性能略低．     

Nd对Mg-6Al铸态合金拉伸性能的影响

研究Nd对Mg-6Al铸态合金拉伸性能的影响。结果表明：室温和175 ℃下,Mg-6Al-xNd(x=0,2,4,6,质量分数, 下同)合金的屈服强度随Nd含量增加而增加,在6.0%Nd时达到最大;抗拉强度和延伸率在4.0%Nd时达到最大,当Nd含量上升至6.0%时,两者均有少量下降。组织分析表明,Nd在Mg-6Al中以针状Al11Nd3和多边形状Al2Nd相存在,其中前者含量明显高于后者,为主要析出相。Al11Nd3相析出于枝晶界和晶界,有效细化了枝晶间距和晶粒度。通过建立软硬体复合模型对合金拉伸过程进行力学分析,并结合拉伸断口观察,综合认为Mg-6Al-xNd合金拉伸性能的提高主要归结于Al11Nd3相引起的细晶强化和第二相强化作用。Nd含量达到6.0%时合金抗拉强度和延伸率出现少量下降,主要归结于大块脆性相Al2Nd含量的增加     

Nd对Mg-4Al-1Sr合金显微组织及力学性能的影响

研究了Nd含量(0、1.0%、2.0%、3.0%)对Mg-4Al-1Sr合金显微组织及室温、高温力学性能的影响.研究结果表明,合金中添加Nd后,细化了合金晶粒,形成高熔点的针状强化相Al11Nd3,很大程度上提高了合金力学性能.当Nd含量达到2.0%时,合金的室温、高温抗拉强度分别达到了206 MPa和138 MPa,比未添加Nd时提高了20%和14%.随着Nd含量的进一步增加,合金中析出了大块状Al2Nd相,该相的形成降低了合金的力学性能.     

Ca和Sr对AE41合金压蠕变行为的影响

采用自制实验装置研究了ca和Sr对AE41(Mg-4A1-RE)合金高温压蠕变行为,并利用XRD和SEM对合金压蠕变前后的组织进行了分析.结果表明:在150℃和100 MPa条件下,添加一定量的Ca和Sr后合金的稳态蠕变速率和总蠕变量均小于AE41合金,改善了AE41合金的抗蠕变性能.铸态AE41合金由a-Mg基体和AI11Nd3相组成.在高温蠕变条件下,针状AI11Nd3相不稳定易发生分解,导致AE4l合金抗蠕变能力下降.在AE41合金中加入Ca和Sr后,针状Al11Nd3逐渐被Al2Ca、Al4Sr及少量的Al2Nd代替.分布在晶界的Al2Ca和Al4Sr有很高的热稳定性,提高了合金的抗蠕变性能.     

含Sr和Ca的Mg-12Zn-4Al-0.3Mn合金的显微组织和力学性能

以Mg-12Zn-4Al-0.3Mn(质量分数,%)为母合金,制备了6种合金.实验观察证实,Mg-12Zn-4Al-0.3Mn合金的铸态组织由α-Mg基体和沿晶界分布的准晶Q相组成.在母合金中加入少量的Sr后,亚稳准晶相转变为Mg32(Al,Zn)49平衡相以及Mg51Zn20共晶相.在母合金中复合加入Sr与Ca后,铸态组织出现了Al2Mg5Zn2共晶相.随着Sr含量的增加,合金室温和高温下的力学拉伸强度提高,高温蠕变性能下降;Sr与Ca的复合加入使合金抗拉强度和塑性下降,但高温屈服强度提高.在175℃/70 MPa条件下,Mg-12Zn-4Al-0.2Sr-0.4Ca-0.3Mn合金表现出良好的高温抗蠕变性能.     

Mg-Al-M合金中Al-M相(M=Sr,Nd)析出行为的热力学分析

以Al-M（M=Sr，Nd）二元相图、Miedema生成热模型和Toop模型为基础，建立了Mg-Al-M三元合金熔体中Al-M金属间化合物析出行为的热力学计算模型，并采用该模型对Mg-8Al-3．5Sr熔体中A1-Sr金属间化合物的析出温度进行了计算，结果与文献基本吻合．利用该模型对一定温度下Mg-9／6Al-M（M=Sr，Nd）熔体中优先析出Al-M金属间化合物所需M的最低含量进行了计算．根据计算结果，对Al-M金属间化合物在Mg-9／6Al-M合金熔体中的析出行为以及对合金力学性能可能的影响进行了分析和比较，提出了采用稀土Nd和碱土Sr复合添加来制备耐热镁合金的思路．     

钇钕复合合金化对Mg-6Al合金力学性能的影响

研究了Y、Nd复合合金化(Y:Nd=2:1,wt%)对Mg-6Al合金显微组织和力学性能的影响.结果表明,添加稀土元素Y和Nd可显著提高合金从室温至175℃区间的屈服强度和抗拉强度.在Mg-6Al合金中加入总含量为0.9wt%～3.6wt%的Y Nd后,合金的晶粒得到明显细化,且出现Al2Y、Al2Nd高熔点稀土合金相.并探讨了钇钕复合合金化对提高镁铝基合金力学性能的机理:室温下主要是细晶强化机制;高温下则主要是高熔点稀土合金相(Al2Y、Al2Nd)的弥散强化,并由此使热稳定性差的β-Mg17Al12相的数量减少.     

La和Nd复合添加对AZ91镁合金铸态组织和性能的影响

利用SEM和XRD等方法研究了总添加量为2.5%(质量分数, 下同)的单加或复合添加La和Nd的AZ91镁合金的铸态显微组织和相组成,并测试和分析了合金的室温力学性能。结果表明：单加或复合添加2.5%的La和Nd使AZ91合金中的β相Mg17Al12数量明显减少。单加La和单加Nd在AZ91合金中形成的稀土相分别是针状的Al11La3和块状的Al2Nd;二者复合加入时两种稀土相同时出现,Al11La3相和Al2Nd相的尺寸较单加时有所减小,其相对含量与两种稀土元素添加量成正比。当复合添加La和Nd时,Al11La3相中的部分La和Al2Nd相中的部分Nd分别被Nd和La置换。相对于单一添加,复合添加La和Nd能更显著地改善AZ91的力学性能。本实验研究的合金中,AZ91+1.0%La+1.5% Nd合金力学性能最好,其铸态合金的抗拉强度和延伸率分别为235 MPa和10%     

Microstructure and strengthening mechanisms of Mg-6Al-6Nd alloy

The microstructure and strengthening mechanisms of as-cast Mg-6Al-6Nd alloy were studied. The results show that the addition of 6 wt.% Nd into Mg-6Al alloy leads to the precipitation of Al11Nd3 and Al2Nd phases and decrease in the content of Al solid soluted in Mg-Al matrix. The volume fractions of Al11Nd3 and Al2Nd phases are 3.64% and 0.34%, respectively. Compared with Mg-6Al alloy, the ultimate strength, yielding strength, and elongation of Mg-6Al-6Nd alloy at room temperature and 175°C are enhanced in some degrees. The strengthening mechanisms of Mg-6Al-6Nd alloy are mainly composed of solid solution strengthening of Al solid soluted in Mg-Al matrix and grain refinement strengthening, dispersion strengthening, and composite strengthening brought by the precipitation of Al11Nd3 phase. The composite strengthening includes the load transfer from the matrix to Al11Nd3 phase and the enhancement of dislocation density due to the geometrical mismatch and thermal mismatch between the matrix and Al11Nd3 phase.     

均匀化退火对Mg-3Al-1Zn-2.2/5Sr镁合金中第二相的影响

为研究均匀化退火处理对Mg-3Al-1Zn-2.2/5Sr镁合金中第二相的影响,通过X射线衍射分析(XRD)、扫描电镜观察(SEM)和能谱分析(EDS)等手段,并结合Pandat热力学计算软件,对Mg-3Al-1Zn-2.2/5Sr镁合金均匀化退火后组织中的第二相的类型及形成原因进行了分析。结果表明:经过400℃,15 h(炉冷)的均匀化退火处理以后,合金铸态组织中原本存在的(Mg,Al)17Sr2相中固溶的Al元素所占原子分数有所降低。此外,Sr含量为2.2%(质量分数)的合金组织中可以观察到大量沿(Mg,Al)17Sr2相边缘分布的颗粒状Al4Sr相,而Sr含量为5%的合金中基本观察不到(Mg,Al)17Sr2相的变化。     

锶、钕对Mg-9Al-1Si-0.3Zn合金微观组织和力学性能的影响

当镁合金中添加含量较高的Si时,会形成大量粗大汉字状的Mg2Si,严重影响合金的力学性能。通过Sr和Nd及其复合添加细化Mg-9Al-1Si-0.3Zn合金中粗大的Mg2Si,研究添加元素对合金微观组织和室温力学性能的影响,分析了Sr和Nd对Mg2Si的细化机制。结果表明,随着Sr的加入,汉字状Mg2Si的形貌得到改善,形成了均匀的多边形块状;当Sr添加到0.16%(质量分数,下同)时,Mg2Si得到了完全的细化。当同时添加Nd和Sr元素时,合金中出现新的以Mg,Al,Nd和Si形成的物相;随着Nd的增加,这种新的物相增多,这种化合物提供了Mg2Si相细化的异质核心。在Sr和Nd的复合作用下,汉字状Mg2Si被细化,合金的力学性能得到改善。     

Microstructure and creep properties of Mg-4Al-2Sn-1 （Ca,Sr） alloys

The effects of Ca and Sr addition on the microstructure and creep properties of Mg-4Al-2Sn alloys were examined.Tensile tests at 25℃ and 200℃ and creep tests at 150℃ and 200℃ were carried out to estimate the room temperature and high temperature mechanical properties of these alloys.The microstructure of the Mg-4Al-2Sn alloy showed dendriticα-Mg,Mg17Al12 and Mg2Sn phases.The latter two phases precipitated along the grain boundaries.The addition of Ca and Sr resulted in the formation of ternary CaMgSn and SrMgSn phases within the grain.The grain size was reduced slightly with the addition of Sr and Ca.The tensile strength was decreased by the addition of Ca and Sr at room temperature.However,the high temperature tensile strength was increased.The creep strength was improved by the addition of Ca and Sr.     

Effect of Nd content on microstructure and mechanical properties of as-cast Mg-12Li-3Al alloy

In order to improve the mechanical properties of Mg-Li alloy with single β phase structure, Mg-12Li-3Al-xNd(x=0.3, 0.7, 1.1, 2.0wt.%) alloy was prepared. Subsequently, the as-cast microstructure and mechanical properties were observed and tested. The results showed that the structure of Mg-12Li-3Al-xNd(x=0.3, 0.7, 1.1, 2.0wt.%) as-cast alloy was composed of β phase matrix and Al_2Nd, Al_(11)Nd_3, MgLiAl_2, Al_4Li_9 and AlLi phases. With the increase of Nd content in the alloy, the Al-Nd intermetallic compounds have a trend to change from needle-like Al_(11)Nd_3 to granular Al_2Nd. The hardness of as-cast Mg-12Li-3Al-xNd(x=0.3, 0.7, 1.1, 2.0wt.%) alloy was stable at room temperature. The tensile strength of Mg-12Li-3Al-1.1Nd was as high as 180 MPa, the elongation rate of Mg-12Li-3Al-0.7Nd reached 53.7%, and the comprehensive mechanical properties of Mg-12Li-3Al-2.0Nd was the best. PLC phenomenon occurred during the tensile process of the alloys at room temperature. Therefore, the β-based Mg-Li alloy with good plasticity as well as enhanced strength can be obtained by a moderate addition of Nd and Al.     

Sm对Mg-6Al-1.2Y-0.9Nd合金组织和性能的影响

采用XRD、OM、SEM和EDS等手段研究Sm对Mg-6Al-1.2Y-0.9Nd合金微观组织和力学性能的影响。结果表明,合金中加入Sm后,Sm优先与A1形成高熔点Al2Sm弥散颗粒质点,当Sm含量(1.5%～2.0%)较高时,合金内出现针状Mg12Nd相。在研究范围内,随Sm含量的增加,合金的常温和高温力学性能略有升高然后降低;而合金的延伸率呈现不断降低的趋势。合金的拉伸断口为具有塑性特征的准解理断裂。     

Microstructure and mechanical properties of Mg-6Al magnesium alloy with yttrium and neodymium

The effects of rare earth (RE) elements Y and Nd on the microstructure and mechanical properties of Mg-6Al magnesium alloy were investigated. The results show that a proper level of RE elements can obviously refine the microstructure of Mg-6Al magnesium alloys, reduce the quantity of/β-Mg17Al12 phase and form Al2Y and AI2Nd phases. The combined addition of Y and Nd dramatically enhances the tensile strength of the alloys in the temperature range of 20-175℃. When the content of RE elements is up to 1.8%, the values of tensile strength at room temperature and at 150℃ simultaneously reach their maximum of 253 MPa and 196 MPa, respectively.The main mechanisms of enhancement in the mechanical properties of Mg-6Al alloy with Y and Nd are the grain refining strengthening and the dispersion strengthening.     

Sn对Mg-6Al-1.2Y-0.9Nd镁合金组织和耐蚀性能的影响

用静态失重法、金相显微镜、扫描电子显微镜等方法研究了不同含量的Sn对Mg-6Al-1.2Y-0.9Nd镁合金的微观组织以及在3.5%NaCl腐蚀介质中的腐蚀速率和表面腐蚀形貌的影响。结果表明,添加1%Sn 时,合金的晶粒得到了明显的细化,组织和成分更加均匀;当Sn含量大于1%时,合金的析出相增多,并出现粗化、偏聚的趋势。在NaCl溶液中,合金的腐蚀速率均随着Sn含量的增加呈现先降低后增加的趋势,其中当Sn含量为1%时合金的腐蚀速率均达到最低,耐蚀性能得到明显地改善。     

As-cast microstructure of Al-Zn-Mg and Al-Zn-Mg-Cu alloys added erbium

1 INTRODUCTIONMany researches show that the properties ofaluminum and its alloys can be remarkablyi mproved withreasonable rare earth additions .Theactions of rare earth elements in the aluminumalloys consist in alterant-agent , micro-alloying andso on[1 3].By far element scandiumis the most ef-fective rare earth element which i mproves thealuminum alloys properties[4 6]. However , theprice of scandiumis very high.Therefore ,it s veryessential to find a new rare earth element , whichacts …