热处理对Mg-8Li-4Zn-3Y合金组织和性能的影响

采用锂盐熔剂保护法熔铸Mg-8Li-4Zn-3Y合金,并对合金进行T4固溶和T6固溶+时效热处理,探讨了热处理对Mg-8Li-4Zn-3Y合金组织及硬度的影响。结果表明,T4固溶后,组织中的强化相减少,α-Mg相晶粒尺寸增大,形貌亦变得不规则,合金的硬度下降;再经过T5时效后,组织中又析出一些强化相颗粒,合金的硬度有一定程度的提高。压缩过程中,Mg-8Li-4Zn-3Y合金试样均呈鼓形后开裂,且均呈45°的剪切断裂。     

稀土Y元素对铸态镁合金组织与力学性能的影响

采用熔炼工艺制备了Mg-2.0Zn-0.2Ca与Mg-2.0Zn-0.2Ca-2Y合金,研究了两种合金的铸态组织及力学性能。结果表明,Y元素的添加细化了Mg-2.0Zn-0.2C合金的铸态组织。Mg-2.0Zn-0.2Ca合金主要由α-Mg与少量Mg₇Zn₃相组成,添加2wt%的Y后,改变了Zn在Mg基体中的固溶度,降低了其固溶强化效果,同时组织中形成了I相和W相。添加Y元素后,合金的规定塑性延伸强度升高,从41.0 MPa升高到50.6 MPa;伸长率降低,从12.6%降低到4.0%。     

添加Zn、Y对Mg-7Li合金变形行为及应变率效应的影响

利用金相显微镜、扫描电子显微镜、X射线衍射仪、电子拉伸试验机等对挤压态Mg-7Li合金及Mg-7Li-3Zn-6Y合金的显微组织和力学行为进行研究。结果表明:Mg-7Li合金及Mg-7Li-3Zn-6Y合金热挤压后均发生了动态再结晶,且Zn、Y的添加使Mg-7Li-3Zn-6Y合金的晶粒显著细化;随着应变率提高,两种合金均表现出应变率强化效应,且添加Zn、Y后合金的强度明显提高、塑性降低,同时,塑性不稳定性得到抑制;两种合金的微观断裂机制均为微孔聚合型断裂与沿晶断裂的混合机制,但添加Zn、Y后合金断口中沿晶断裂的比例明显增大。     

Mg-6Zn-1Y-Zr镁合金的组织与性能研究

Mg-6Zn-1Y-Zr镁合金在热锻或热挤压过程中发生了动态再结晶.合金组织细化,但不均匀,平均晶粒尺寸约10 μm.挤压态材料经350℃×30 min再结晶退火转变为等轴细晶组织,平均晶粒尺寸已达到5μm左右.合金在变形处理后有新的第二相析出,且合金的力学性能有很大提高.其中锻态Mg-6Zn-1Y-Zr合金的σb达到265 MPa,σ0.2达155 MPa,挤压态合金的σb达到330 MPa,σ0.2达185MPa.     

Mg-11Gd-3Y合金组织与力学性能分析

采用XRD、SEM和拉伸力学性能测试方法,分析了铸态和固溶时效态Mg-11Gd-3Y合金的显微组织和力学性能。结果表明,热处理没有改变Mg-11Gd-3Y合金相的组成,合金铸态和固溶时效态组织均由α-Mg基体、Mg_5Gd和Mg_(24)Y_5相组成。固溶时效态合金的强化机制主要为固溶强化和时效强化,其最大抗拉强度为230 MPa,比铸态合金提高了12%。     

挤压态和时效态Mg-Zn-Mn-Sn-Y合金的组织性能

利用光学显微镜、X射线衍射和扫描电镜等对挤压态和时效态Mg-6Zn-1Mn-4Sn和Mg-6Zn-1Mn-4Sn-0.5Y镁合金的微观组织和力学性能进行研究。结果表明：与ZMT614镁合金相比,添加Y元素后,ZMT614-0.5Y晶粒得到细化,综合力学性能得到提高。Mg-6Zn-1Mn-4Sn-0.5Y合金的相组成为α-Mg、Mg Zn2、Mn、Mg2Sn和MgS n Y相。经过T6热处理后,合金的抗拉强度和屈服强度明显得到提高,伸长率明显被降低。理论计算表明,在挤压态合金中,细晶强化和固溶强化产生重要的作用,而在T6热处理态合金中,析出强化产生决定作用。     

高Y添加量对Mg-2Zn-1Mn合金组织和力学性能的影响

采用光学显微镜、X射线衍射仪、X射线荧光法、电子探针显微分析仪、扫描电子显微镜、电子背散射衍射、透射电子显微镜和单轴拉伸测试等对Mg-2Zn-1Mn-x Y (x=0,1,3,5,7,质量分数,%)合金的显微组织和力学性能进行研究。结果表明：随着Y元素的加入,铸态合金的第二相由Mg₇Zn₃转变为Mg₃Zn₃Y₂,最终转变为Mg₁₂ZnY。Y元素的加入阻碍了动态再结晶的生长过程,使晶粒得到细化,但是进一步增加Y含量不会继续增强晶粒细化程度。挤压态Mg-2Zn-1Mn合金加入Y元素后,塑性呈现出先升高后下降的趋势,这可能是受到了织构取向变化和晶粒粗化的共同影响。此外,合金强度提高主要是由于细晶强化和第二相强化作用。Mg-2Zn-1Mn-7Y合金具有最佳的力学性能,其抗拉伸强度为357 MPa,屈服强度为262 MPa,延伸率为14%。     

Zn含量对Mg-xZn-3Y-0.7Zr合金组织和性能的影响

采用低压铸造制备了Mg-xZn-3Y-0.7Zr合金,利用金相显微镜、扫描电镜、能谱分析仪、热分析仪等设备,研究了Zn含量对合金微观组织的影响,并通过热处理工艺来改善合金微观组织中的第二相分布,从而提高合金的力学性能。结果表明,Mg-5Zn-3Y-0.7Zr合金主要含有α-Mg和W-Mg3Zn3Y2相,其中W相呈网状在晶界上分布;当Zn含量为8%时,铸态组织中树枝晶明显增多,并且出现了I-Mg3Zn6Y相;热处理后I相消失,网状分布的W相被打断,在三角晶界处仍有鱼骨状片层共晶组织。Mg-5Zn-3Y-0.7Zr合金铸态抗拉强度、屈服强度和伸长率分别为223.8MPa、124.9MPa和7.3%,经过T6处理后提升效果不明显,而Mg-8Zn-3Y-0.7Zr合金在铸态时力学性能较差,经过T6处理后其抗拉强度、屈服强度和伸长率为263.3 MPa、207.9 MPa和2.2%。Mg-5Zn-3Y-0.7Zr合金的断裂机制为准解理断裂,断口处有发生塑性变形而出现的撕裂棱。Mg-8Zn-3Y-0.7Zr合金的断裂机制主要为解理断裂,并没有发现韧窝。     

挤压铸造压力对Mg-4Zn-1.2Y合金组织及力学性能的影响

采用显微组织观察、拉伸试验、密度测试等研究了不同挤压铸造压力对Mg-4Zn-1.2Y合金显微组织与力学性能的影响。结果表明:随着挤压压力的增加,Mg-4Zn-1.2Y合金的平均晶粒尺寸和第二相体积分数逐渐减小,挤压压力从0增加到150 MPa时,合金晶粒细化明显,挤压压力超过150 MPa后,合金晶粒细化趋势变缓。随着挤压压力的增加,Mg-4Zn-1.2Y合金的抗拉强度、屈服强度、伸长率及密度均逐渐增加。与挤压压力为0 MPa的合金相比,挤压压力150 MPa的合金抗拉强度、屈服强度和伸长率分别提高了24.4%、23.3%和72.7%,力学性能显著提高,挤压压力超过150 MPa后,合金力学性能提高幅度变缓。     

稀土Y对Mg-Zn-Mn镁合金显微组织和力学性能的影响(英文)

研究不同稀土Y含量对Mg-6Zn-1Mn合金显微组织和力学性能的影响。结果表明:Y元素的添加对Mg-6Zn-1Mn合金的相结构、组织和力学性能有明显的影响。随着Y含量的增加,合金中的第二相依次从Mg7Zn3相、I相(Mg3YZn6)、I相+W相(Mg3Y2Zn3)到W相+X相(Mg12YZn)转变;热分析和组织观察证明合金相的稳定性趋势为X相W相I相Mg7Zn3相;Mn元素主要以单质颗粒形式弥散分布在基体中;Y的添加能显著提升Mg-Zn-Mn合金的力学性能,其中含6.09%Y的挤压态合金具有最佳的力学性能,其抗拉强度和屈服强度分别达到389 MPa和345 MPa。合金强度的提升主要源于Y元素的晶粒细化、Mn颗粒的弥散强化和Mg-Zn-Y稀土相的引入。     

Phase diagrams of binary systems: AgNO3KNO3 and AgNO3 -@#@ NaNO3

AgNO₃-KNO₃ and AgNO₃-NaNO₃ phase diagrams were drawn using a simultaneous thermal analysis technique in the range 373 to 623 K. The apparatus is described briefly. Figure 1 shows a continuous solid solution in equilibrium with the liquid phase. It exhibits a eutectoid mixture (20 mol% NaNO₃) at 380.7 K. Figure 2 shows a eutectic mixture (45 mol % KNO₃) at 413 K, a eutectoid mixture (20 mol % KNO₃) at 409 K, and a continuous invariant at 404 K.     

Thermodynamic analysis of the CsNO3-KNO3-NaNo3 system

The thermodynamic properties of the CsNO₃-KNO₃-NaNO₃ system have been derived from an optimization procedure using experimental and published information concerning phase diagram and thermodynamic data for the constituent binary systems and ternary liquid phase. The results are in very close agreement with the experimental data.     

3-D or not 3-D

When developing mathematical models of physical phenomena, physical scientists have been limited to two-dimensional solutions. In some cases, those solutions may be qualitatively correct, but in many others, the solutions are far from reality. This paper presents three examples of the limitations of two-dimensional modeling :diffusion-limited electrolytic reduction of a liquidproduct from a liquid electrolyte, morphological development of a solid dendrite, and behavior of a two-phase fluid under shear.     

三自由度并联机构（3SPS 3SRR）的位置分析

针对一种3SPS-3SRR并联机构,运用符号法对该机构进行位置分析建模及求解。构建动、静坐标系,通过矩阵转换对机构建立约束方程,运用Sylvester消元方法进行消元得到机构单变元输入输出方程,求得机构位姿的封闭解。最后进行实例求解,得到该机构处于一般姿态的32组实数解,并使机构处于特殊位姿,将所得封闭解与预估解对比,从而验证该位置求解模型的正确性。基于符号法的3SPS-3SRR并联机构位置分析模型具有准确、高效的特点,规避了基于数值法的诸多缺点,对该机构的深入分析具有重要理论意义及实用价值。     

GdF_3:Ce~(3+),Ln~(3+)(Ln~(3+)=Eu~(3+),Tb~(3+),Dy~(3+),Sm~(3+))纳米晶体的制备与发光性能研究

应用共沉淀法,制备共掺同一敏化剂(Ce3+)和不同激活剂(Tb3+,Eu3+,Sm3+,Dy3+)的GdF3纳米晶体。在单一波长(254nm)紫外光的激发下,掺杂不同镧系激活离子的样品能够发射出不同颜色的明亮可见发光,因而适用于多色生物标记。     

3

In this paper, a planning algorithm for multi-path/multi-layer circular locus is poposed. The algorithm is applied to weld the nipples on the header of boiler. Multi-path/multi-layer circular locus is planned according to three teaching points, which is lapped head-on-end to satisfy the requirement of technology. For the nipples wherever they are arranged radially or axially, even if there are errors caused by positioning and thermal deformations, providing that nipple's position and orientation relative to the teaching one can be measured, the multi-path/multi-layer circular locus can be planned without teaching any more. The algorithm has been applied in welding robot for manufacturing power station' boiler.     

Electronic structures of semiconducting FeGa3, RuGa3, OsGa3, and RuIn3 with the CoGa3- or the FeGa3-type structure

Electronic structure of FeGa₃, RuGa₃, OsGa₃ and RuIn₃ with the crystal structures belonging to the space group of P4n2 (No. 118), which is usually referred to as the CoGa₃-type structure, and P4₂/mnm (No. 136), which is usually referred to as the FeGa₃-type structure, have been calculated using a first-principle pseudopotential method based on the density-functional theory within the local density approximation (LDA) with the generalized gradient correction. All of them have the similar band structure in that the valence band maximum occurs at or near A and the conduction band minimum occurs at a point between Z and Γ. From the total energies calculated, compounds with the FeGa₃-type structures are more stable than those with the CoGa₃-type structures. The band gaps of FeGa₃, RuGa₃, OsGa₃ and RuIn₃ with the FeGa₃-type structure are about 0.50, 0.26, 0.68, and 0.30 eV, respectively, which are wider than those with the CoGa₃-type structure. Calculated band gaps are wider than the observed gaps, which is unusual in the LDA calculation.     

PMN-PNN-PT陶瓷晶粒异常长大研究

采用两步法和等离子放电烧结技术制备出了致密的单一钙钛矿相的PMN-PNN-PT陶瓷,对其高温热处理后晶粒异常长大进行了研究.发现添加5%(质量分数)过量PbO有助于晶粒的异常长大,观察到了3种典型的异常长大晶粒,为下一步固态法制备该组成单晶打下了基础.     

BiFeO3-BaTiO3-LaFeO3三元多铁性陶瓷材料的制备及性能

采用固相法制备了1-x(0.71BiFeO3-0.29B aTiO3)-xLaFeO3 (x=0.0,0.1,0 2,0 3,0 4,0.5)三元多铁性陶瓷材料,并研究了LaFeO3含量对陶瓷物相结构、微观组织、电学性能和磁电耦合性能的影响。结果显示,所有陶瓷均为单一钙钛矿结构,但随LaFeO3含量的增加,伴随着结构相变。所得陶瓷晶粒尺寸均匀,表现出良好的微观形貌,陶瓷晶粒随LaFeO3含量的增加而明显变小。虽然LaFeO3的加入在一定程度上降低了陶瓷的介电常数,但分析发现,x=0.1时能降低陶瓷的漏导,其漏电流达到了最小值,在10-7~10-8 A/cm2数量级,并且该陶瓷的剩余极化强度Pr和磁电耦合系数αME均达到最大值,分别为0.45μC/cm2和132.21 mV/cm·Oe (120 kHz)。因此,与0.71BiFeO3-0.29BaTiO3陶瓷相比,添加少量LaFeO3可以在一定程度上增加陶瓷的铁电性和磁电耦合性能。     

Features of feathery γ structure in a near-γ TiAl alloy

This work characterizes the feathery-like structures produced in a Ti–46.8Al–1.7Cr–1.8Nb (at.%) alloy during rapid continuous cooling from the α domain. Their morphology and crystallography are described using different microscopy and orientation mapping techniques. These feathery-like structures are divided into many small domains, characterized by low-angle misorientations (rotated less than 15°) between the domains. The domains comprise multiple parallel γ lamellae and rare traces of α₂. These lamellae follow the Blackburn orientation relationship and have a {1 1 1}_γ habit plane. Two types of γ-feathery structures were identified according to their location and crystallography. The grain-boundary γ-feathery structures originate from lamellar structures that grow into a neighboring grain. Alternatively, the internal γ-feathery structures are located in the interior of prior α grains and show an average misorientation of 36° around one $〈100{〉}_{{\mathrm{\gamma }}_{\text{L}}}$ axis of the lamellar structure in which it is embedded. This paper describes these two γ-feathery structures in detail and discusses their development in light of the mechanisms available in the literature, particularly sympathetic nucleation.