快速凝固Cu-Cr-Zr-Mg合金的时效析出与再结晶

对快速凝固Ｃｕ０．６Ｃｒ０．１５Ｚｒ０．０５Ｍｇ合金伴随时效析出的再结晶过程进行了观察和研究。发现该合金在形变后的时效过程中,析出相非常细小、弥散,阻碍了再结晶的进行,出现了原位再结晶与不连续再结晶同时发生的现象。在再结晶的形核和长大过程中,析出相在晶界前沿快速粗化或重新溶解,并在再结晶区域中重新析出,导致更加弥散的析出相分布。     

Al5TiB对Mg-8Zn-4Al-0.3Mn合金时效过程的影响

研究了Al5TiB加入量对Mg-8Zn-4Al-0.3Mn铸造镁合金时效过程的影响. 结果表明, 未加Al5TiB的Mg-8Zn-4Al-0.3Mn合金的时效析出过程为 过饱和固溶体→细小弥散析出相→再结晶软化和析出相的聚集长大; 添加Al5TiB的Mg-8Zn-4Al-0.3Mn合金的时效析出过程为 过饱和固溶体→细小弥散析出相→析出相的聚集长大. 固溶处理后, 与未加Al5TiB的合金1#相比, 合金2#、3#、4#显微硬度值分别提高了2.8%、6.8%、9.1%; 人工时效后, 与未加Al5TiB的合金1#相比, 合金2#、3#、4#显微硬度峰值分别提高了9%、11.2%、5.2%. 随着Ti元素在合金中含量的增加, 合金的析出相形成激活能呈先增大而后减小的变化规律.     

铜碲合金时效工艺的研究

研究了铜碲合金的时效工艺，用扫描电镜(SEM)和能谱(EDS)分析了析出相的形貌与组成，进而研究了时效工艺对其电性能及力学性能的影响。研究表明：时效过程中Te以第二相形式析出(Cu2Te)；随时效温度的升高、时效时间的延长，时效态的铜碲合金位错密度降低，晶粒长大，第二相析出充分，因而电阻率单调下降；但由于时效析出与再结晶的交互作用，其抗拉强度出现波动，存在1个峰值；综合性能以420℃下时效6h较好。     

Cu-0.3Cr-0.15Zr-0.05Mg合金形变时效强化与再结晶

对Cu-0．3Cr-0．15Zr-0．05Mg合金形变时效强化和再结晶过程进行了考察和研究。析出相对位错的钉扎作用强烈阻碍合金再结晶的形核和长大，使合金产生明显的时效硬化。60％冷变形450℃～500℃时效1h～2h，硬度和导电率分别可达162HV和73％IACS左右。大变形量降低了合金再结晶激活能(Qr)，加速再结晶过程，以致于在较高温度下时效，出现了再结晶形核和长大的现象，再结晶产生的软化导致析出硬化程度下降。     

时效工艺对Ti-26合金棒材组织和拉伸性能的影响

对经过790℃固溶处理后的Ti-26合金棒材进行了不同温度及时间的时效处理，研究了时效温度和时间对Ti-26合金棒材显微组织和拉伸性能的影响。研究结果表明：在450-550℃范围内，随时效温度升高，合金组织有针状“相弥散物析出。升温至510℃，相同时效时间内析出α相数量最多，高于510℃，部分析出α相开始溶解。合金时效处理10h内，随时效时间延长，合金组织针状α相弥散物数量增加，且针状α相存在跨晶界长大现象。合金经510℃×10h时效处理，OL相形核和长大达到最佳匹配，Ti-26合金获得理想的强度和塑性匹配。     

Pd-Ag-Sn-In-Zn合金时效特性

研究了不同时效工艺对Pd-Ag-Sn-In-Zn合金的力学性能、电学性能及显微组织和相结构的影响.结果表明:固溶-冷变形后合金的时效过程由过饱和固溶体的析出和基体的再结晶两个过程控制;合金高强度主要来源于加工硬化和第二相的析出强化,合金的电阻率变化主要受时效过程中再结晶和析出过程的综合影响.     

铸造高温合金K480及DD407热处理中γ'相的析出行为

选取两种典型铸造高温合金DD407及K480,研究其固溶及时效过程中γ'相析出行为。结果表明,经热力学平衡相图计算获知,铸造高温合金K480及DD407合金的凝固温度范围是158、30℃,室温下γ'相体积分数分别为54%,80%;合金在凝固或固溶后的冷却过程中,γ'相形核率低,长大速率高,γ'相粒子易于长大;当其尺寸超过临界尺寸就会发生分解;两合金经过固溶后,较大尺寸的一次γ'相溶解后重新析出较小的二次γ'相;在一次时效空冷热处理后,合金在立方状的二次γ'相通道周围析出弥散细小球形三次γ'相;经过二次时效后,三次γ'相回溶、扩散直至消失,同时二次γ'相进一步长大,立方度增加。     

Mg-x%Zn-1%Mn（x=4,5,6,7,8,9）变形镁合金的组织演变和力学性能

研究不同Zn含量的Mg-x%Zn-1%Mn（x=4,5,6,7,8,9）变形镁合金经热机械处理后的显微组织和力学性能的演变。在热挤压过程中,显微组织经动态再结晶得以充分细化。随着Zn含量的增加,动态再结晶晶粒有长大的趋势,然而,随之增加的第二相流线阻碍其长大。固溶处理使动态再结晶晶粒快速长大,但高Zn含量会阻碍晶界迁移,从而使最终的晶粒较为细小。在单级时效过程中,与基体共格的MgZn2弥散相会从过饱和固溶体中析出;在双级时效时,预时效过程中析出的大量纳米尺度的GP区为第二级时效过程中MgZn2相的析出提供了有效的异质形核核心,从而使该强化相的弥散度增加。挤压态试样的力学性能对Zn含量的变化不敏感,抗拉强度在300-320MPa之间波动,伸长率在11%-14%之间波动。时效态试样的强度随着Zn含量的增加以抛物线形式增加,单级时效态试样的抗拉强度从278MPa增加到374MPa,而双级时效态试样的抗拉强度从284MPa增加到378MPa,但所有试样的伸长率都小于8%。当Zn含量超过其在Mg-Zn二元合金体系中的最大固溶度（约6.2%）后,合金的强度增加缓慢但伸长率却迅速降低。因此,含6%Zn的Mg-Zn-Mn合金具有最佳的力学性能,即经过单级和双级时效后,合金的抗拉强度分别为352MPa和366MPa,伸长率分别为8%和5%。     

Zr对Al-Zn-Mg-Cu合金组织和性能的影响

研究了Zr对Al-Zn-Mg-Cu合金显微组织和力学性能的影响。结果表明,添加少量Zr可以细化合金铸态组织,并且在热挤压过程中抑制再结晶。在固溶时效过程中,可以促进第二相粒子的析出,从而使基体中析出均匀弥散第二相粒子。T6状态下,未加Zr的合金其抗拉强度仅为600MPa,伸长率为10.5%;而加Zr后其抗拉强度超过650MPa,伸长率达到12.3%。     

冷轧Cu-Cr-Zr-Co-Si合金的时效行为

通过测量Cu-Cr-Zr-Co-Si冷轧合金在等温时效过程中导电率的动态变化,基于合金导电性能与析出相转化率间的近似线性关系,建立了不同冷变形量下合金时效析出过程的动力学Avrami方程及曲线,在此基础上分析了再结晶与时效析出的相互影响。结果表明:Cu-Cr-Zr-Co-Si合金形变时效过程中,随变形量和时效时间的增加,导电率及析出相转化率均增加,这是时效过程中再结晶与时效析出相互影响、共同作用的结果。随冷变形量增加,强化相析出进程明显加快,但时效析出没有明显阻止或延缓再结晶软化过程的发生,因此大冷变形+短时时效使合金获得更高的硬度峰值,但无法同时获得最优的导电性能。只有在时效析出提前于再结晶启动,且形成的第二相对再结晶存在明显阻碍的前提下,采用冷变形+时效工艺,时效强化型铜合金才能达到最佳效果。     

INTERACTION OF PRECIPITATION AND RECRYSTALLIZATION IN RAPIDLY SOLIDIFIED Cu-Cr-Zr-Mg ALLOY

1.IntroductionCu--Cr-Zr-Mgalloysarewidelyusedinvariousaspects,suchasinelectricresistanceweldingelectrode,motor--commutatorandintegratedcircuitleadframe,duetotheirgoodthermalandelectricalconductivitiesandrelativelyhigherstrength.However,itisdifficulttofurtherimprovetheirelectricalandmechanicalpropertiesunderconventionalsohltionheat--treatment(CSHT)sincethedegreeofprecipitationhardeninguponagingisrestrictedbythelimitedsolubilityofchromiumandzirconiumincopper[1--31.Thecompositionsandthepropert…     

Mechanism and kinetics of discontinuous precipitation of the η phase in the 36NKhTYu alloy

A new mechanism of nucleation and growth of cells of the η phase in the deformed 36NKhTYu austenitic alloy has been found. The recrystallization nuclei are formed at the η-phase particles, which were precipitated according to the continuous mechanism. Simultaneously, they are nuclei of cells of discontinuous decomposition. Unlike the known growth mechanism, the η-phase cell grows in all directions until it collides with other cells. The Peterman-Hornbogen theory of discontinuous precipitation has been modified to describe the kinetics of the complex reaction of discontinuous precipitation of the η phase and recrystallization and also the kinetics of complex reaction of discontinuous coalescence of grains and phases. The theoretical dependences of the cell size on the aging time for these reactions are proportional to t ^1/3 and t ^1/4, respectively. A comparison of the theoretical and experimental results has been performed.     

挤压和热处理过程中AZ91镁合金的组织变化(英文)

对AZ91镁合金在均质化热处理、热挤压和时效处理中的组织演化规律进行研究。研究结果表明,在铸态组织中存在离异共晶和固态析出两种β-Mg17Al12相。在最佳的均质化处理(380℃,15h)过程中,β-Mg17Al12相大部分溶解到α-Mg基体中,并且晶粒细小。在热挤压过程中发生动态再结晶以及由此产生的晶粒细化。而时效处理之后则出现平行于挤压方向的带状β-Mg17Al12相析出,这应该是由于在挤压过程中把原始铸造偏析挤扁拉长而造成的。另外,根据实验结果,详细地讨论了均质化和时效处理的温度、保温时间以及挤压工艺参数对AZ91镁合金的组织变化产生的影响。     

Study on the Precipitation of gamma ' in a Fe-Ni Base Alloy During Ageing by APTEI北大核心CSCD

High strength Fe-Ni base austenitic alloys, such as A286 and JBK-75, are widely used in gas turbine jet engines and hydrogen service and so on because of their excellent corrosion resistance and low hydrogen embrittlement sensitivity. The ordered coherent gamma' [Ni-3(Al, Ti)], precipitated during ageing, is thought to have the main contribution on the strength. Thus, it is very important to understand the characterization of the precipitation. However, few previous studies are focused on atomic scale evolution of the precipitated phase. Atom probe tomography (APT) is a unique microscopy technique that provides 3D analytical mapping of materials at near atomic resolution and a high detection sensitivity for all elements. The present research is focused on the microstructure evolution at ageing temperature at different time scales using APT. A Fe-Ni base austenite alloy were aged at 620 degrees Cfor different time after solution treated at 980 degrees C for 2 h. Hardness testing indicates that a sharp increase is observed when the ageing time is less than 6 h. The hardness is up to 205 HV from the initial 145 HV at the ageing time 6 h. After that the hardness increases slowly. The hardness is 251 HV at 120 h. APT results reveal that Ti-rich nano-clusters precipitate obviously at the initial stage of ageing, which contain Fe, Cr, Ni, Mo and Al elements. As the ageing time increases, more Ni and Al atoms are segregated in the Ti-rich nanoclusters while the Fe, Cr and Mo are ejected from the nanoclusters. When the ageing time is up to 120 h, the Ni/(Ti+Al) ration is approximately close to 3. The precipitates can be identified as gamma' phase. The results reveal that the formation of gamma' involves nucleation and growth. Effect of the number density and the size of the gamma' precipitates on the hardening of the alloy has been estimated.     

Relating Initial Texture to Deformation Behavior During Cold Rolling and Static Recrystallization Upon Subsequent Annealing of an Extruded WE43 Alloy

Deformation behaviors during cold rolling and static recrystallization behaviors upon subsequent annealing of an extruded WE43 alloys with different initial textures were investigated in this study. Three types of differently textured WE43 initial alloys were labeled as samples I, II and III. The results showed that multiple twinning modes and basal slip dominated the deformation of samples during cold rolling. Cold-rolled sample I activated the larger number of double twins with high strain energy, accompanied by the more uniform strain distribution, than cold-rolled samples II and III. During subsequent annealing, recrystallized grains preferentially occurred in double twins, twin-twin intersections and grain boundaries, thereby making cold-rolled sample I have the more rapid recrystallization rate. Similar recrystallization textures formed in three types of cold-rolled samples at the recrystallization nucleation stage, and they never largely changed with the annealing time due to the uniform grain growth induced by the solute drag and the precipitation pinning at grain boundaries. After full recrystallization, the grain growth was controlled by the solute drag, instead of precipitates which were re-dissolved into the matrix. Finally, the nucleation and growth kinetics of static recrystallization were calculated, and the effects of initial texture on activation energies of recrystallization nucleation and growth were discussed.     

Zn-8Cu-0.3Ti锌合金热变形的组织演变(英文)

利用Gleeble-1500热力模拟试验机在温度230~380°C,应变速率0.01~10 s-1的条件下进行均匀化态Zn-8Cu-0.3Ti锌合金的热压缩变形实验,测定真应力—真应变曲线,利用OM、SEM和TEM对变形组织进行分析。结果表明:在变形过程中该合金发生了TiZn15相的球化、析出相的粗化和基体η相的动态再结晶,形成了(η+ε+TiZn15)复相组织。变形过程中TiZn15相的球化有助于粒子协同方式实现粒子激发形核,有利于基体动态再结晶的发生。随着压缩变形温度的升高,基体动态再结晶晶粒的尺寸先减小后增大;随着应变速率和应变量的增大,动态再结晶进行得更充分;形变促进Cu原子的扩散,导致析出相的粗化,析出相的钉扎作用使组织得到细化。     

相场法预测低铝合金Ni75AlxV25-x的早期沉淀过程

采用微观相场模型,通过分析原子图像、有序相内序参数分布及有序相体积分数随时间的变化,在原子尺度对低Al浓度Ni75AlxV25-x合金的早期沉淀动力学进行了计算机预测．研究发现该合金沉淀过程中,析出D022结构的θ(Ni3V)相和L12结构的γ‘(Ni3Al)相,二者构成伪二元系;θ相先于γ‘析出,θ相的沉淀机制为等成分有序化 失稳分解,γ‘在θ相的相界处非经典形核,二者均先形成非化学计量比有序相,之后向化学计量比有序相转变;随Al浓度增加,θ相析出变慢,所占比例减少,而γ’相反之,析出越来越早且所占比例增加。     

Dynamic recrystallization and silicide precipitation behavior of titanium matrix composites under different strains

In order to elucidate the microstructure evolution and silicide precipitation behavior during high-temperature deformation, TiB reinforced titanium matrix composites were subjected to isothermal hot compression at 950 °C, strain rate of 0.05 s⁻¹ and employing different strains of 0.04, 0.40, 0.70 and 1.00. The results show that with the increase of strain, a decrease in the content, dynamic recrystallization of the α phase and the vertical distribution of TiB along the compression axis lead to stress stability. Meantime, continuous dynamic recrystallization reduces the orientation difference of the primary α phase, which weakens the texture strength of the matrix. The recrystallization mechanisms are strain-induced grain boundary migration and particle stimulated nucleation by TiB. The silicide of Ti₆Si₃ is mainly distributed at the interface of TiB and α phase. The precipitation of silicide is affected by element diffusion, and TiB whisker accelerates the precipitation behavior of silicide by hindering the movement of dislocations and providing nucleation particles.     

Al-Zn对称成分合金不连续析出组织的再结晶

采用光学显微镜、扫描电镜和透射电镜研究了Al 4 0 %Zn(摩尔分数 )二元合金的不连续析出细片层组织在冷轧后重新加热时所发生的再结晶。根据加热过程中的显微组织变化 ,确定了该合金再结晶的形核及长大机制。结果发现 ,再结晶的 2种机制为非典型形核长大机制的连续粗化和典型形核长大机制的不连续粗化 ,后者又分为在团域界面、滑移带等处发生的以变形储能为主要驱动力的粗化和在变形量很小区域发生的以界面能为主要驱动力的粗化。