Mg-Zn-Ca系富Mg区域三元化合物及其固态相平衡

利用SEM,EPMA,XRD和TEM对Mg-Zn-Ca系富Mg区域三元化合物的成分、结构及其相平衡进行了研究.结果表明,Mg-Zn-Ca系富Mg区域存在2个可与镁基固溶体相平衡的三元化合物T1和T2.其中化合物T1为线性化合物,成分(原子分数,%,下同)为:Ca约16,Zn 16.8-49.5,Mg余量;晶体结构为六方...     

Mg-Zn-Ca系富Mg侧三元化合物及其300℃固态相平衡

采用合金平衡组织结构分析法,利用扫描电镜组织观察、电子探针定量成分分析以及X射线衍射和透射电子衍射结构分析,对Mg-Zn-Ca系富Mg区域300°C的相平衡关系及平衡相成分进行研究。结果表明：300°C时,2个三元化合物T1和T2都可与Mg基固溶体相平衡。T1相是一个线性化合物相,成分为15%Ca（摩尔分数）,20.5%～48.9%Zn,余量为Mg。T1相为六方晶体结构,晶格常数为：a=0.992～0.945nm,c=1.034～1.003nm,随T1相中Zn含量的增加而减少。化合物T2相也是六方结构,成分为26.4%～28.4%Mg,63.2%～65.5%Zn以及7.1%～8.4%Ca。300°C时,Zn在Mg基固溶体中的溶解度随Ca的加入而增大,最大溶解度达到3.7%。在Mg-Zn-Ca系中300°C等温截面相图的富Mg区域存在着三相区α-Mg＋Mg2Ca＋T1,α-Mg＋T1＋T2,α-Mg＋T2＋MgZn和MgZn＋T2＋Mg2Zn3。     

Ni-Co-Sn三元系相平衡的实验研究

本实验通过采用电子探针显微分析和X-ray衍射分析方法实验研究了Ni-Co-Sn三元体系在700°C和1000°C时的相平衡。在这两个温度截面中均未发现三元化合物。βCo3Sn2相和Ni3Sn2（h）相形成了一个贯穿连续固溶体相。Ni-Sn侧包含Ni3Sn（l）、Ni3Sn（h）和Ni3Sn4三个化合物相,它们中Sn的固溶度是有很大区别的。700°C时,Co在Ni3Sn（l）和Ni3Sn4中的最大固溶度在分别约为6.9 at.%和25.6 at.%,在1000°C时,Co在Ni3Sn（h）中的最大固溶度约为15.5 at.%。在700℃和1000℃下,Ni-Co侧的（αCo,Ni）相为一个贯穿连续固溶体相,并且Sn在（αCo,Ni）相中的固溶度约为1 at.% ~10.5 at.%。Ni在线性化合物CoSn相中的溶解度约为15.9 at.%。     

Mg-Zn-Ca系低Ca侧400℃相平衡研究

利用SEM,EPMA,XRD和DSC,对Mg-Zn-Ca系镁基固溶体400℃时的溶解度以及镁基固溶体与化合物之间的平衡相关系进行了研究.结果表明,在Mg-Zn系中加入Ca后,T₁和T₂相在400℃时依然是富Mg角的主要三元化合物,但只有T₁相与镁基固溶体相平衡,且α-Mg+T₁两相区明显缩小.400℃时,Mg-Zn-Ca系低Ca侧存在一个可与镁基固溶体相平衡的液相区,其含Ca量小于8.4%（原子分数）;但Zn/Ca值小于1.7的三元合金中不会有液相存在.Mg-Zn-Ca系低Ca侧400℃等温截面相图中存在着4个三相区:α-Mg+Mg₂Ca+T₁,α-Mg+T₁+Liq,Liq+T₁+T₂和Liq+T₂+Mg₂Zn₃.     

Mg-Sn-Y三元系富Mg角500℃等温截面的测定

采用合金法,利用XRD、SEM-EDS测定一系列Mg-Sn-Y三元合金在500℃下富Mg角处相平衡关系及各相平衡成分,建立Mg-Sn-Y三元系在500℃下富Mg角处的等温截面相图。结果表明:Mg-Sn-Y三元系富Mg角处存在Mg2Sn、MgSnY、Sn3Y5和Mg24+xY54种化合物与α-Mg固溶体平衡,从而构建3个三相区和4个两相区;Sn在α-Mg基体中的固溶度为2.5%～3.9%(摩尔分数),Y在α-Mg基体中的固溶度为1.1%,但二者不能同时固溶到α-Mg基体中,同时Sn3Y5相中大约可以固溶3.6%～4.1%的金属Mg;由于MgSnY和Sn3Y5等一些高熔点化合物在高温下能够稳定存在,使得Mg-Sn-Y体系有可能成为一种潜在的新型耐热镁合金。     

Al-Zn-Mg-Cu系富铝角相平衡计算及实验研究

采用Thermo-Calc软件计算和光学显微镜、扫描电镜、能谱仪及示差扫描量热仪实验分析手段,研究了Al-Zn-Mg-Cu系富铝角等温(480℃)截面图和Al-12Zn-xMg-1.5Cu合金的垂直截面图。结果表明,相平衡计算结果与实验分析吻合良好。在等温等锌截面计算相图中,随着Zn含量提高,α(Al)单相区和α(Al)+S(Al2CuMg)相区分别缩小和扩大,在α(Al)单相区内,Mg在铝固溶体的固溶度降低,Cu的固溶度变化不大。在等温等铜截面计算相图中,随着Cu含量降低,α(Al)单相区扩大,α+S(Al2CuMg)两相区缩小。合金元素的极限固溶度对温度极为敏感,在多相共晶点附近温区,合金元素的极限固溶度最大。     

Co-Ti-Ta三元系富Co区的相平衡

研究Co-Ti-Ta三元系富Co区的相平衡。显微组织和XRD分析以及EDS检测结果表明,在1000～1200℃温度范围内,L12结构Co3Ti相和Laves_36_Co3Ta相与α-Co构成相平衡。Co3Ti相中Ta的固溶度超过10%,Ta的加入使Co3Ti相更稳定。根据实验结果构建Co-Ti-Ta三元系富Co区在1000、1100和1200℃等温截面图。     

Co-Cu-Zn三元系相平衡的实验研究

本实验通过采用电子探针显微分析和X-ray衍射分析方法实验研究了Co-Cu-Zn三元体系在800°C和1000°C时的相平衡。在这两个等温截面中均未发现三元化合物。在800°C等温截面,Co在β-CuZn相中的固溶度为32.36%,Cu在β1-CoZn相中的固溶度为5.28%。除此之外,γ-Co5Zn21和γ-Cu5Zn8具有相同的晶体结构,因此,它们之间形成了一个贯穿连续固溶体相。1000°C的等温截面中,β-CuZn相、β1-CoZn相、γ-Co5Zn21相、γ-Cu5Zn8相都消失了。随着温度从800°C上升到1000°C,液相区域增大。     

Phase equilibria in the Mg-rich corner of the Mg-Zn-La system at 350℃

The phase equilibria in the Mg-rich comer of the Mg-Zn-La system at 350℃ have been investigated by scanning electron microscopy, X-ray diffraction, and electron probe microanalysis. It has been shown that the linear compound （Mg,Zn）17La2 existed in the Mg-Zn-La system at 350℃. The linear cornpound （so-called Tphase） was with the C-centred orthorhombic crystal structure induced by the solution of significant quantities of the third element. The three-phase region α（Mg） ＋ MgZn（La） ＋ T and the two-phase region composed of the α（Mg） and the linear-compound T phase existed in the Mg-rich comer of the Mg-Zn-La system at 350℃.     

Nb-Ni-Ti系低Ni侧1000℃相平衡研究

利用SEM、EPMA、XRD、DSC对Nb-Ni-Ti系低Ni侧1000℃的液相相关相平衡进行了研究。结果表明,1000℃时,在Nb-Ni-Ti系低Ni侧存在着一个可与(Nb,bTi)连续固溶体和TiNi化合物相平衡的液相区;该液相区源自Ti-Ni二元系,延伸至Nb含量3.7%(原子分数)。而二元化合物TiNi在1000℃时则可以溶解约8.0%Nb。1000℃时,Nb-Ni-Ti系低Ni侧等温截面相图中存在2个三相区Liquid+(Nb,bTi)+TiNi和(Nb,bTi)+TiNi+XB,XB是成分为34.0Nb-44.9Ni-21.1Ti的六方结构化合物;这2个三相区之间则是宽阔的(Nb,bTi)+TiNi两相区。在该两相区内,连续固溶体(Nb,bTi)中的Ni含量变化不大、约为3%,Ti含量的变化范围为6.6%~39.9%。而3.7%Nb的溶入未能使二元化合物Ti_2Ni相的稳定存在温度提高到1000℃。     

Phase equilibria in the Mg-rich corner of the Mg-Zn-La system at 350℃

The phase equilibria in the Mg-rich corner of the Mg-Zn-La system at 350℃ have been investigated by scanning electron microscopy, X-ray diffraction, and electron probe microanalysis. It has been shown that the linear compound (Mg,Zn)17La2 existed in the Mg-Zn-La system at 350℃. The linear compound (so-called T phase) was with the C-centred orthorhombic crystal structure induced by the solution of significant quantities of the third element. The three-phase region α(Mg) + MgZn(La) + T and the two-phase region composed of the α(Mg) and the linear-compound T phase existed in the Mg-rich corner of the Mg-Zn-La system at 350℃.     

Measurement of phase equilibria in Ti-Ni-Sn system

Phase relations of the Ti-Ni-Sn ternary system were investigated via alloy sampling assisted with X-ray diffractometry (XRD) and electron probe micro-analysis (EPMA). A new binary phase with composition of TiSn₄ (molar fraction, %) was detected at 508 K. In addition, a supplementary phase (Ti_1–x–yNi_xSn_y)Ni₃ (τ, AuCu₃-type) was observed at 873 and 973 K. According to the characterised microscopic structure in various annealed alloys, four ternary phases were detected in Ti-Ni-Sn ternary system: TiNiSn, TiNi₂Sn, Ti₂Ni₂Sn and (Ti_1–x–yNi_xSn_y)Ni₃. Additionally, isothermal sections of Ti-Ni-Sn ternary system at 508, 873 and 973 K were constructed. By comparing three isothermal sections, a peri-eutectic reaction, L+TiNi₂Sn→Ni₃Sn₄+TiNiSn, was deduced, which occurs at a temperature between 873 and 973 K. Furthermore, the solubility of Sn in TiNi and Ni in Ti₅Sn₃ was detected.     

Phase equilibria in the Mg-rich corner of the Mg-Zn-La system at 350°C

1. Introduction Mg-based alloys are attractive for applications because of the light weight and a high specific strength. Among the common alloying elements, the addition of zinc could make the magnesium alloys strengthen by precipitation [1-2]. The further addi- tion of the rare-earth elements to the Mg-Zn alloys is more effective on the precipitation-strengthening [3-4]. But phase diagrams of the Mg-Zn-RE system, as the basis of the alloying, have hardly been built up [5-6]. The phase equ…     

Experimental determination of phase equilibria in the Fe---Al---C system

The phase equilibria in the Fe---Al---C system have been determined between 800 °C and the liquidus surface. From cast alloys the liquidus surface was established. From electron microprobe analyses (EPMA) of quenched samples three isothermal sections at 800, 1000 and 1200 °C have been obtained. Additional high temperature X-ray diffraction experiments (HT-XRD) yielded three vertical sections and the temperatures of four invariant reactions. The influence of carbon on the transition temperature between the disordered (A2) and the ordered (B2) -solid solution was determined from HT-XRD experiments with single crystals. This transition is shifted remarkably to higher temperatures by the addition of carbon. Special emphasis was placed on establishing the homogeneity range of the K-phase and its dependence on temperature. This dependence is discussed in terms of order/disorder. In addition, the properties of the K-phase, lattice constant as function of chemical composition, microhardness and thermal expansion coefficient , have been determined.     

Phase equilibria on the ternary Mg–Mn–Ce system at the Mg-rich corner

Three isopleths at the Mg-rich corner of Mg–Mn–Ce ternary system were investigated via thermal analysis, SEM/EPMA and XRD. A ternary eutectic reaction was observed at 1 wt.% Mn and 23 wt.% Ce and 592 °C. A solid-solution type ternary intermetallic compound, (Mg,Mn)₁₂Ce, was observed with 0.5 at% solid solubility of Mn in the tetragonal Mg₁₂Ce. With the aid of thermodynamic modeling and experiments, a revised phase diagram for the binary Mg–Ce system and the isopleths of 0.6, 1.8 and 2.5 wt.% Mn were proposed up to 25 wt.% Ce.     

Solid-state phase equilibria in the Titanium-Aluminum-Nitrogen system

The 1273K isothermal section of the Ti-Al-N phase diagram was studied using modern methods of physical and chemical analyses. The data obtained by various techniques are in good agreement and in harmony with the results of thermodynamic calculations. It has been reliably established that AIN can coexist with TiN_1−x , Ti₂AIN, and TiAl₃; the ternary nitride Ti₂AIN can be in equilibrium with TiAl₃, AIN, TiAl₂, TiAl, TiN_1−x , and Ti₃AIN; the solid solution based on α(Ti) coexists with Ti₃Al, Ti₃AIN, TiN_1−x , and Ti₂N. Literature data on phase equilibria in the Ti-Al-N system were analyzed, and a 1273 K isothermal section of the phase diagram has been suggested.     

Ni-Al-Sn三元系相平衡的实验研究

采用电子探针显微分析和X-ray衍射分析方法实验研究了Ni-Al-Sn三元体系在800°C和1000°C时的相平衡。结果表明：(1) Ni-Al-Sn三元体系在800°C和1000°C时均未发现三元化合物;(2) Ni-Al侧包含NiAl、Ni3Al、Al3Ni和Al3Ni2四个化合物,其中800°C时,Sn在NiAl和Ni3Al中的固溶度在分别为3.1和14.7 at.%,在1000°C时分别为3.0和8.0 at.%。而Sn在Al3Ni和Al3Ni2相中几乎没有固溶度;(3) Ni-Sn侧包含Ni3Sn(r)、Ni3Sn(h)和Ni3Sn2(h)三个化合物相。800°C时,Ni3Sn(r)相的固溶度为4.2 at.%,1000°C时,Ni3Sn(r)相转变为Ni3Sn(h)相,拥有5.5 at.% 的固溶度。另外,800°C时,Al在Ni3Sn2(h)相中的固溶度为8.4 at.%,1000°C时为12.1 at.%;(4) Ni-Al-Sn三元体系Al-Sn侧为相互贯通的液相区域,实验测得的Ni在Al-Sn侧的溶解度约为1 at.%。     

三元扩散偶中的相区分布与四相平衡的关系

根据相区邻接规则和扩散偶中的相区分布的关系，运用三元扩散偶方法确定三元系中的四相转变从而导出三元系中相转变与扩散偶中相区分布的关系，利用Nb-Ti-Si三元系的试验，验证了包共析型转变前后等温截面与扩散中相区分布的关系。