Sn-Sb包晶合金的快速凝固

设计了一种用于Sn-Sb等滑动轴承合金的无容器接触深过冷快速凝固装置.并以热流分析为基础,利用传热模型和物理模型计算了Sn-16%Sb(质量分数)过包晶合金在本装置中的冷却速度.结果表明:在粒子直径为4mm时,粒子的冷却速度为3.1×102K/s;当粒子直径为0.1mm时,冷却速度达到了105K/s.Sn-Sb包晶合金组织显著细化,初生相SnSb化合物高度弥散化.     

金属材料在液态和液固转变过程中磁化率变化的测量方法和装置

提出一种基于电磁感应原理的测量液态金属材料磁化率变化的方法并开发相应装置,分析该装置的基本工作原理。使用该装置测量CuSn合金在温度变化时磁化率的变化情况。实验结果表明,样品在相变点处其磁化率有明显的变化。液态CuSn合金的磁化率的倒数与温度成线性关系,但在925℃附近,其斜率有明显的变化。通过液态合金的粘度实验证实,Cu75Sn25合金的结构在925℃时发生了相应的变化。     

液态Ca70Mg30合金快速凝固过程中纳米团簇结构形成演变特性模拟

采用分子动力学方法对液态Ca70Mg30合金快速凝固过程中纳米团簇结构的形成和演变特性进行模拟。采用原子团类型指数法(CTIM)对凝固过程中纳米团簇结构的演变进行分析。结果表明：系统在5×1011 K/s的冷速条件下形成以1551、1541和1431为主的非晶态结构,非晶转变温度约为530 K;(120120)二十面体基本原子团对系统非晶结构的形成起到决定性的作用,并且原子半径较小的Mg原子更容易占据二十面体基本原子团中心原子的位置;同时,纳米团簇主要是通过中等尺寸团簇的合并而形成,纳米级大团簇的形成演变过程呈现出类似于非晶晶化过程的3个阶段式的变化。     

Temperature-induced liquid state change and its effects on solidification of thermoelectric alloy Bi_（0.3）Sb_（1.7）Te_3

The behaviors of electrical resistivity vs temperature（ρ-T） of the molten p-type thermoelectric alloy Bi0.3Sb1.7Te3（at.%） were explored in heating and cooling processes. An obvious hump appeared on the ρ-T curve from 932 ℃ to 1,020 ℃ at the heating process, while the curve became smooth in the following cooling, which suggests an irreversible temperature-induced liquid-liquid structure transition（TI-LLST） occurred in the liquid alloy. Based on this judgment, solidification experiments were carried out to find out the effects of the different liquid states. It was verified that, for the melt experiencing the presumed TI-LLST, both the nucleation and growth undercooling degrees were elevated and the solidification time was remarkably prolonged. On the other hand, the configuration of Bi0.3Sb1.7Te3 phase was refined, and its preferential orientation was weakened.     

Pb-Sb30%液-液结构转变的不可逆性及其对凝固的影响

在前期研究发现一些二元合金在液相线上数百度温度范围内发生温度诱导液-液结构转变的基础上,进一步研究了Pb-Sb30%合金液-液结构转变的可逆性,结果表明,该合金熔体发生的结构转变是不可逆的;并探讨了液-液结构转变对其凝固行为及组织的影响,发现结构变化后的熔体凝固过冷度增大,初生相和共晶相组织明显细化,且维氏硬度值提高约30%。     

熔体保温条件下超声波对Al—1％Si合金凝固组织的影响

研究了Al-1%Si合金在保温条件下超声波处理对其凝固组织的影响,考察了不同保温温度、不同处理时间及不同冷却方式条件下Al-1%Si合金凝固组织的变化规律。试验表明:在不同保温温度条件下,当保温温度较高时,超声波处理熔体的晶粒细化效果不明显,晶粒粗大;随着保温温度的下降,铸锭中等轴晶的数量先呈递增趋势;当在两相区内进行超声波处理时,晶粒细化效果降低,等轴晶数量明显减少,可以认为存在一个适当的超声波处理温度。此外,坩埚材质和冷却方式对保温处理后熔体凝固组织有很大的影响。     

Effect of the atomic packing density on the structural change rate of amorphous alloys under elastostatic stress

This study deals with the fundamental issue of whether the atomistic-scale structure of amorphous alloys can be altered by the application of elastic stress. The prolonged imposition of elastostatic stress on amorphous alloys induces permanent structural change. The rate of change largely depends on the atomic packing density, which is characterized by the fractions of various short-range ordered clusters. This structural change is accompanied by the formation of excess free volume, which in turn affects the mechanical properties in subsequent compression tests. The findings of the experiments and molecular dynamics simulations were analyzed in terms of atomistic-scale structural changes.     

镁锰合金的晶粒细化及其耐蚀性的研究

通过实验对镁锰合金的晶粒细化和耐蚀性进行了探索.结果表明:在镁锰合金中加入Ca元素可以使其晶粒显著的细化,耐蚀性也得到了很大提高.     

Influence of multi-pass friction stir processing on microstructure and mechanical properties of 7B04-O Al alloy

Three-pass friction stir processing (FSP) with different moving distances of the stirring tool between the two successive passes, 50% diameter of the pin (traditional way) and 50% diameter of the shoulder (novel way), was conducted on 7B04-O Al alloy. The result shows that an improvement in the mechanical properties of the processed zone is accomplished due to grain and second phase particles refinement. The hardness of the multi-pass FSP (M-FSP) sample is about HV 40 higher than that of the base metal. And the tensile strength of the M-FSP specimens is also significantly increased to about 1.4 times that of the base metal. Besides, the weak region of the processed zone is mainly dependent on the moving distance, where it is the previous pass stir zone in the traditional way and the transitional zone in the novel way. Increasing the rotational speed narrows the weak region in the novel way, while it does not in the traditional way.     

Al-Ti-C中间合金对Mg-Al合金的晶粒细化作用

制备了一种用于Mg-Al合金晶粒细化的Al-Ti-C中间合金。发现该Al-Ti-C中间合金可以有效地细化镁合金的晶粒，细化后的AZ61合金的抗腐蚀性能大大提高。分析认为，Al-Ti-C中间合金中起晶粒细化作用的是Al4C3和TiC的复合相。     

Mg—Al—C中间合金对AZ91镁合金组织和性能的影响

通过真空烧结制备出Mg—Al-C中间合金，发现该合金可以有效地细化Mg-Al系AZ91合金的晶粒，细化后的AZ91合金力学性能显著提高，粗大且易于聚集成团的Mg17Al12相得以消除；分析认为其细化机制是在镁合金熔体中形成了大量的结晶形核质点Al4C3或Al-C-O化合物。     

时效工艺对Al-Zn-Mg-Cu铝合金组织与性能的影响

向Al-Zn-Mg-Cu合金中添加0.22%的过渡族元素Ti,通过一级时效、二级时效与三级时效工艺处理,研究了时效工艺对含Ti铝合金的组织与性能的影响。利用光学显微镜(OM)、扫描电镜(SEM)、微控万能试验机、显微硬度计等测试合金铸态组织及相析出分布形态、时效后力学性能与断口形貌等。结果表明:添加Ti元素可以细化晶粒、改善枝晶偏析并强化合金;一级时效态合金具有最高强度586 MPa,三级时效态合金具有最大硬度与最长伸长率,强度与一级时效态相当,分别为183.2 HV0.1、8.8%和579 MPa。三级时效对合金的力学性能提高最显著。     

镁合金新型复合挤压的有限元和实验研究

针对镁合金的棒材的工业化制备和加工,提出了一种新型的镁合金复合挤压方法,将正挤压(Extrusion)和剪切(Shear)结合(简称ES),建立了ES挤压的三维有限元热力耦合模型及条件,模拟了ES挤压的流动网格、累积应变演化,设计并制造了适合于卧式挤压机上的ES挤压模具,进行了ES工艺实验。数值模拟结果表明,ES挤压可以显著提高镁合金变形过程的累积应变;试验结果表明,ES挤压可以得到尺寸很小的动态再结晶晶粒,并改善了组织均匀性;理论分析表明,ES挤压过程镁合金具有多级动态再结晶的特性,可以逐步有效的细化微观组织。ES挤压在模具结构、工艺参数合理的条件下可以大大细化镁合金微观组织,并具有工业生产的实用性。     

Grain refinement of Sn-Pb alloy under a novel combined pulsed magnetic field during solidification

The combined pulsed magnetic field (C-PMF) obtained by simultaneously imposing pulsed and static magnetic field during solidification has been proposed to refine the solidification structure. Compared to the imposition of a single pulsed magnetic field, a more refined structure can be observed under C-PMF. The key factors to affect grain refinement under C-PMF consisted of the vibration frequency characterized by the static magnetic field, pulsed discharge voltage, and the vibration frequency characterized by the pulsed discharge frequency. The microstructure revealed that the grain size decreased with the increasing static magnetic field. The pulsed discharge voltage had an optimum value for obtaining fine grains. Furthermore, when the pulsed discharge frequency was equal to the intrinsic frequency of the liquid metal in a filled cylindrical vessel, resonance vibration occurred in the liquid surface, and grain refinement was promoted.     

高密度脉冲电流对A356铝合金凝固组织的影响

研究了高密度脉冲电流对A356铝合金凝固组织的影响，实验中对液相线以下溶体的凝固过程在不同阶段进行电脉冲处理。对比实验结果表明：经过电脉冲处理后，A356的合金凝固组织得到明显细化；在同样的电脉冲条件下，凝固组织细化效果与电脉冲放电开始时间有关，凝固过程中放电开始时间越早，凝固组织细化效果越明显；反之，凝固组织细化效果较差；同时，脉冲充电电压越高，凝固组织细化程度越大。定量计算了脉冲电流产生的电磁力并分析了脉冲电流影响凝固组织的作用机制。     

简析铝合金加钛的经济效益

钛是铝及铝合金铸造时常用的晶粒细化剂,也是对晶粒细化最有效的元素之一,对某些铝合金还是一个微量合金化元素。钛剂与铝一钛一硼中间合金是常用的添加钛的载体,在钛价不甚贵的过去,多用钛剂,但在钛价高昂的今天,用Al—Ti—B中间合金不但经济效益更好一些,而且产品品质也更有保证。     

冷却条件对镁合金耐蚀性能的影响

通过浸泡腐蚀质量损失试验,研究了不同凝固冷却速度(空冷、水冷和盐水冷)对AZ31和AZ81镁合金在3.5%Na Cl溶液中耐腐蚀性能的影响。研究结果表明,镁合金中Mg17Al12相的尺寸、形貌、分布、析出量及合金凝固组织的均匀性对抗Na Cl溶液腐蚀产生重要影响;Mg17Al12相对镁合金耐蚀性能具有双重作用(起阻障及电偶阴极的作用);同时凝固组织均匀化程度的改善能提高耐蚀性能。在3种因素的叠加作用下,AZ31合金的耐蚀性能随着冷却速度的提高而得以改善,而AZ81合金的耐蚀性能则表现为:空冷盐水淬水冷。     

AZ31镁合金晶粒细化方法及机制研究现状

系统介绍了AZ31镁合金晶粒细化方法及机制,综述了6种制备细晶镁合金大塑性变形方法的工艺特点和应用,展示了大塑性变形方法在AZ31镁合金加工中的应用前景。     

加钛和加硼方式对铝合金的晶粒细化及其衰退行为的影响

通过对比实验,研究了电解加钛与经Al-Ti、Al-Ti-B中间合金向工业纯铝熔配加钛的晶粒细化效果及其衰退行为,以及Al-B中间合金对电解低钛铝合金的晶粒细化效果及衰退行为的影响,还分析了硼对电解低钛铝合金的晶粒细化和抗衰退行为的影响.结果表明,在钛含量为0.10%和0.15%的条件下,电解加钛晶粒细化作用的衰退速度比熔配加Al-Ti中间合金要慢;熔配加Al-Ti-B中间合金细化晶粒作用的抗衰退能力则明显高于电解加钛和熔配加Al-Ti中间合金;加Al-B中间合金可有效提高电解低钛铝合金的细化效果和抗衰退能力,并使其明显高于电解加钛和熔配加Al-Ti或Al-Ti-B中间合金.     

Effects of grain refinement on mechanical properties and microstructures of AZ31 alloy

Cerium was added in AZ31 alloy with the contents of 0.4%,0.8%and 1.2%respectively to produce experimental alloys. The grain refinement of Ce in the as-cast and rolled AZ31 alloy were studied by using Polyvar-MET optical microscope with a VSM2000 quantitative analysis system,KYKY2000 SEM and Tecnai G~2 20 TEM.And the mechanical properties of AZ31+Ce alloy were tested on a CSS-44100 testing system with computerized data acquisition.The results show that the cerium has a good grain refinement effect on the ...