Cu-0.8Cr-0.3Zr-0.2Mg合金热变形行为及热加工图

采用Gleeble-1500D数控动态-力学模拟试验机,对Cu-0. 8Cr-0. 3Zr-0. 2Mg合金在550～900℃温度范围和0. 001～10 s~(-1)应变速率条件下进行了热变形试验,绘制了其真应力-真应变曲线,利用光学显微镜分析了其在热变形过程中的组织演变。绘制了合金的热加工图,找出热变形过程中最适宜的热加工参数。结果表明:合金的流变应力随温度的降低和应变速率的提高而增大;在热变形过程中,合金组织的演变对温度和应变速率有很高的敏感性,高温低应变速率有利于促进动态再结晶的发生;Cu-0. 8Cr-0. 3Zr-0. 2Mg合金适宜的热加工参数范围为:变形温度为850～900℃,应变速率为0. 01～0. 07 s~(-1)。     

Ti-6Al-3Nb-2Zr-1Mo合金片层组织热加工行为

利用Gleeble-1500热模拟试验机对Ti-6Al-3Nb-2Zr-1Mo合金片层组织进行热压缩实验,实验温度为850～1050℃,应变速率为0. 01～1 s~(-1),变形量为60%。实验结果表明,热加工温度一定时,流变应力随变形量和应变速率的增加而急剧增加直至达到峰值,然后下降,最后趋于平缓,这是由加工硬化和动态再结晶所致。应变速率恒定时,随着变形温度的上升,流变应力随之降低。绘制应力-应变曲线,计算其热变形激活能Q为748. 845 k J·mol~(-1),构建本构方程,并在动态材料模型的基础上建立了热加工图。并通过加工图确定3个失稳区,变形温度为980～1030℃、应变速率为0. 3～1 s~(-1)时合金发生剪切,形成绝热剪切带。结合加工图,确定了适合的加工区域,即加工温度为970～1010℃,应变速率为0. 03～0. 07 s~(-1)。     

汽车用5182铝合金热变形行为及加工图研究

在Gleeble-3800热模拟机上采用等温压缩实验研究了5182铝合金在变形温度为573 K～723 K、应变速率为0. 01 s-1～10 s~(-1)、真应变为0～0. 69条件下的高温流变应力行为,建立了5182铝合金热变形的本构方程和热加工图。结果表明:5182铝合金在热变形时,其流变应力呈现出稳态流变特征,随变形温度的升高而降低,随应变速率的增加而增大,但在应变速率ε·≥1 s~(-1)高应变速率下,则出现动态软化现象;可以采用包含Z参数的双曲正弦函数关系来描述5182铝合金高温变形时的流变应力行为;最佳的热变形区域为变形温度400℃～420℃、应变速率0. 01 s~(-1)～0. 1 s~(-1)。     

特大型支承辊用Cr4合金钢的热变形行为及热加工图

采用Gleeble-1500热模拟实验机在温度为700~1200℃,应变速率为0.002~5 s~(-1)、最大变形量为55%条件下对特大型支承辊Cr4合金钢进行热压缩试验,研究了该合金的热变形行为及热加工特征,建立了Cr4合金钢在试验条件下的热加工图。结果表明:在其他变形参数恒定时,Cr4合金钢的热变形真应力随应变速率的升高而逐渐变大,随变形温度的提高而急剧降低;在变形温度为750~900℃,应变速率为0.002~0.01 s~(-1),变形温度为750~800℃,应变速率为0.049~2.718 s~(-1)和变形温度为800~1050℃、应变速率为0.1~4.482 s~(-1)的3个区域内易产生流变失稳现象;动态再结晶是触发材料流变软化及稳态流变的主要原因,Cr4合金钢的安全热加工区域的变形温度在950~1150℃之间、应变速率在0.018~0.223 s~(-1)之间。     

新型建筑用铝锰合金的热变形行为

在Gleeble-3800热模拟试验机对新型Al-Mn-Er-Zr合金屋面板进行了高温热压缩变形,研究了变形温度350～550℃、应变速率0. 01～10 s~(-1)范围内的热变形行为,建立了热变形本构方程和热加工图。结果表明,建立的热变形本构方程计算得到的峰值应力与实测值基本吻合,峰值应力实测值和计算值的误差在6%以内,可以较好地对Al-Mn-Er-Zr合金的高温流变行为进行预测; Al-Mn-Er-Zr合金在变形温度450～550℃、应变速率为0. 1 s~(-1)时不会发生流变失稳,且功率耗散因子较大,较容易热加工,为适宜的热加工区域。     

燃料包壳用FeCrAl合金变形行为与热加工图研究

通过热模拟压缩试验研究了燃料包壳用FeCrAl合金在形变温度为800～1000℃、应变速率为0.001～1s~(-1)工艺条件下的热变形行为,采用Arrhenius双曲线正弦函数模型建立了FeCrAl高温变形本构方程,结合动态材料模型绘制了FeCrAl在应变量为0.05～0.8的热加工图。结果显示,FeCrAl流变应力随着变形温度的升高而降低、随着应变速率的升高而增大,变形温度与应变速率均会影响其组织演化。根据热加工图,FeCrAl流变失稳区随着应变量的增加先扩展后趋于稳定,其最佳热加工工艺参数确定为:应变量ε=0.1时,应变速率e0.008 s~(-1)、变形温度为880～1000℃;应变量ε≥0.3时,应变速率e0.027 s~(-1)、变形温度950℃。     

欠时效态7075铝合金热变形行为及热加工图

采用Gleebe-3500型热模拟试验机对7075铝合金进行等温恒应变速率热压缩实验,研究了该合金在变形温度为250~450℃、应变速率为0.001~1 s~(-1)条件下的热变形行为,并据此建立了热加工图。结果表明:流变真应力随应变速率的升高而增大,随变形温度的升高而减小;经250℃、16 h欠时效处理的样品,其峰值应力要显著大于未经时效的样品;真应变为0.3和0.7的热加工图在250~350℃的温度区间、0.01~1 s~(-1)的应变速率区间均出现流变失稳;16 h欠时效态7075铝合金的最佳热变形参数为:变形温度400~450℃、应变速率0.01~0.001 s~(-1)。     

Inconel X-750合金的热变形特性

通过热压缩实验,研究了Inconel X-750镍基高温合金在变形温度为950～1200℃,应变速率为0. 1～10 s~(-1),变形量为50%的热变形行为。研究结果表明:变形温度为1100和1200℃,应变速率为0. 1和1 s~(-1)时,合金在热变形过程中可以达到动态平衡,在其余变形条件下,合金在热变形过程中均出现连续的流变软化现象,合金的热变形激活能为377. 12 k J·mol~(-1)。通过建立材料的动态模型,制作了合金的热加工图,发现合金的功耗效率等值线在温度为1075～1085℃时,由于γ'相的溶解而发生转折,结合合金的热变形组织演变过程,确定合金在变形温度为1100～1200℃、应变速率为0. 1 s~(-1)时可以得到均匀细小的再结晶组织。     

新型高密度DT740合金热变形行为及热加工图

利用Gleeble-3800热模拟试验机对新型高密度DT740合金进行轴向热压缩试验,研究该合金在变形温度950～1250℃、应变速率0. 01～1 s~(-1)条件下的热变形行为及组织演变规律,基于双曲正弦本构关系建立其本构方程并依据动态材料模型建立热加工图,分析讨论了不同区域内的高温变形特征,确定该合金最佳的热加工工艺参数。研究结果表明:DT740合金的流变曲线表现出典型的动态再结晶特征,其流变应力随变形温度的降低和应变速率的升高而增加;计算得到该合金的热变形激活能Q为546. 87 k J·mol~(-1);确定了DT740合金最佳的锻造热加工温度范围为1150～1250℃,在此温度范围内合金的热加工性能最佳,可获得均匀、细小的完全动态再结晶组织,能量耗散率η值约为44%。     

基于极性交互模型的MoLa合金锻造工艺优化及热变形行为

采用Geeble1500型热模拟试验,对MoLa合金进行等温恒应变速率压缩实验,研究其在变形温度800～1150℃,应变速率0.001～10s~(-1)范围内的热变形行为。通过对不同变形参数下的流变曲线分析发现,随应变的增加,流变曲线大多呈现为缓慢上升或保持稳定,但在应变速率为0.001 s~(-1)时,1000～1150℃变形温度下流变应力随应变的增加而下降;采用PSO-BP神经网络建立MoLa合金本构模型,经过误差计算得出,该模型的相关系数和平均相对误差分别为:0.995和1.48%,具有良好的精度;基于极性交互模型绘制MoLa合金本征热加工性能参数ξ图,并通过对失稳区和稳定区组织分析发现,失稳区主要以局部流动为失稳形式,稳定区主要以动态回复为变形机制;通过ξ图和组织观察可知,MoLa合金最佳的变形参数范围为:变形温度1100～1150℃、应变速率0.001～0.05 s~(-1)。     

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.