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1.
ECAP细化晶粒法的仿真与分析   总被引:7,自引:0,他引:7  
ECAP(Equal Channel Angular Extrusion)方法,是实现材料纯剪切变形的有效方法。本文采用有限元(FEA)分析软件ANSYS对Al的挤压过程进行仿真与分析。分析结果表明:外切角Φ、圆角半径、试样与凹模之间的摩擦系数、凹模本身的特性(如弹性模量、泊松比等)等等,对材料的变形量都有不同程度的影响。  相似文献   

2.
薛克敏  薄冬青  王薄笑天  刘梅  李萍 《材料导报》2018,32(18):3195-3198, 3212
采用X射线衍射仪、扫描电镜以及光学显微镜等手段对等径角挤压(ECAP)变形前后7A60铝合金多元合金相的演化进行研究。结果表明,轧制态7A60铝合金内部主要存在MgZn_2、Al_2Cu相,等径角挤压工艺可以明显地碎化合金内部的第二相,改善其分布的均匀性;随着变形道次的增加,基体中粗大第二相沿剪切方向发生明显碎化,第二相发生回溶,四道次ECAP变形后第二相碎化成球状,尺寸由5~20μm碎化到1μm左右;初始态7A60铝合金抗拉强度为305MPa,随着变形道次的增加,合金的强度增强,四道后7A60铝合金的抗拉强度为492MPa;拉伸断口表现为韧性断裂,第二相对韧窝的形状和尺寸起决定性作用。  相似文献   

3.
等径通道挤压中晶粒细化影响因素的研究进展   总被引:17,自引:1,他引:17  
本文总结了近些年等径通道挤压(equal-channel angular pressing,简称ECAP)技术晶粒细化的机理、影响晶粒细化的因素及挤压后材料宏观力学性能的改善等方面的研究进展,并结合金属塑性变形理论进行了解释.最后提出了几项需要进一步深入研究的工作.  相似文献   

4.
细化晶粒的新方法——等径转角挤压   总被引:6,自引:0,他引:6  
李伟  郑子樵  李世晨 《材料导报》2001,15(10):25-28
介绍了等径转角挤压(Equal-Channel Angular Pressing)这种细化晶粒的新工艺方法。分析了利用该方法所制备材料的微观结构以及各种工艺参数对材料微观结构和性能的影响。  相似文献   

5.
微合金钢第二相粒子对HAZ区奥氏体晶粒影响   总被引:7,自引:0,他引:7  
研究了Ti-V-Nb微合金钢及热影响区(HAZ)第二相粒子及其对HAZ区奥氏体晶粒长大的影响.结果表明,微合金钢中存在大量弥散分布、细小粒子的Ti、Nb、V的碳氮化合物.这些具有很高的稳定性,在焊接热循环过程中,显著地阻止奥氏体晶粒长大.焊接热循环峰值温度在1200℃以下时,HAZ区中第二相粒子仅发生轻微的溶解及长大,奥氏体晶粒长大程度很小,且奥氏体晶粒尺寸基本不随ts/5及热循环峰值温度Tm的变化而变化.焊接热循环峰值温度在1250℃以上时,HAZ区中第二相粒子显著减少而尺寸显著增大,奥氏体晶粒尺寸随t8/5及Tm的增大而显著增大.  相似文献   

6.
变形方式对含ZrC粒子20Mn2钢晶粒细化的影响   总被引:1,自引:0,他引:1  
研究了恒温压缩与降温轧制对含ZrC粒子20Mn2钢晶粒细化的影响.结果表明,在奥氏体再结晶温度区间(1150℃、1050℃)和形变诱导铁素体相变温度区间(950℃、900℃、870℃、850℃),20Mn2钢的晶粒尺寸均能细化至3~4μm;在1150~870℃的降温轧制中,20Mn2钢的晶粒尺寸细化至1~3μm.分析表明,由于ZrC粒子的形变核心和再结晶核心的作用,含ZrC粒子的20Mn2钢在高温下(1150℃、1050℃)和较低温度下(950℃、900℃、870℃、850℃),变形的晶粒组织分别因奥氏体再结晶和形变诱导铁素体相变及其再结晶而得到细化;在降温轧制时,由于综合了高温奥氏体再结晶和低温形变诱导铁素体相变及其再结晶的细化晶粒效应,而最终获得的晶粒尺寸比恒温变形的更小.  相似文献   

7.
本研究利用多道次等径角挤压工艺制备了超细晶Cu-Cr-Zr合金棒,在450 ℃人工时效4h后,获得最佳综合性能:抗拉强度610 MPa,断裂延伸率12.5%,硬度199 HV,电导率77%IACS。通过EBSD技术和TEM分析,揭示了该工艺条件下合金主要的强化机制:超细晶组织贡献了260.6 MPa,析出相强化贡献了149 MPa,加工硬化效果为163.9 MPa。相比于等径角挤压试样,析出相取代了固溶原子,强化效果显著提高;而位错密度降低,加工硬化效果显著降低。  相似文献   

8.
为了研究Al-Cu合金中两种不同析出相(θ′和θ相)在ECAP变形过程中的变化.采用透射电镜(TEM)和硬度测试方法研究了析出相形貌变化以及对合金性能的影响.结果表明:在本实验中,θ′和θ相其破碎、回溶速度明显不同,两者的破碎方式也不同.θ′相先是与基体失去取向关系,随后从其内部产生位错使其破碎,而θ相是被外部基体位错所切割、破碎.θ′相与位错的相互作用方式类似于绕过机制,θ相与位错的作用方式类似于切割机制.两种状态样品的硬度在变形过程中的变化趋势相同,但在第1道次后θ相状态样品的硬度增加值高于θ′相状态.  相似文献   

9.
以TiO_2粉、C粉、Al粉为原料,利用放热弥散法制备Al-TiO_2-C晶粒细化剂,采用XRD,SEM,EDS等研究不同C与TiO_2比例的细化剂的显微组织,并对工业纯铝进行细化实验。结果表明:Al-TiO_2-C晶粒细化剂析出相为Al3Ti,TiC和Al2O3。当C与TiO_2摩尔比为1∶25~1∶20时,Al-TiO_2-C细化剂组织中Al2O3颗粒数量适中且分布相对弥散。当C与TiO_2摩尔比为1∶20,该细化剂添加量为0.2%(质量分数)时,可将工业纯铝细化到约142μm,且保温1h未出现细化衰退。  相似文献   

10.
本文着重研究了钛盐和硼盐细化剂对 ZA-27合金组织和机城性能的影响。得出细化剂最佳配方和最优工艺参数。试验表明;添加细化剂后,ZA-27合金在强度和硬度基本不变的情况下,延伸率从3~6%提高到12~14%。扩大了应用范围。本文还就细化剂对 ZA-27合金晶粒的细化机理进行了理论探讨。证实了起细化作用的异质晶核 Al_5Ti_2Zn 的存在。对进一步研究有参考价值。  相似文献   

11.
Equal channel angular pressing (ECAP) has the capability of producing ultra fine-grained (UFG) materials bellow the dimension of 1 μm. At present, it is one of the most important methods to get bulk UFG materials. Multi-pass ECAP processes for round workpieces are investigated by using numerical simulations and experimental studies in this paper. The deformation mechanism of ECAP for grain refinement is obtained. Three processing routes A, B and C are simulated in order to study the influence of the processing routes to the deformation uniformity of the workpiece. The finite element (FE) analysis results of the multi-pass ECAP process show that the different processing routes result in the different deformation distributions. The grain in the workpiece is refined obviously after multi-pass pressing. The microstructures of the processed material are more different than that of the microstructure of the annealing initial equiaxed grains. The microstructure evolution of the workpiece can be changed via different processing routes. It is found that route B can get a high angle grain boundaries distribution in the workpiece than other routes. The results of the analysis show that the process of grain refinement can be described as a continuous dynamic recovery and recrystallization. The microstructure evolutions of the grain refinement mechanisms and micro-structural characteristics for different multi-pass ECAP processing routes are verified by using OM (optical model) and TEM (transmission electron microscope) analysis. In addition, the experimental microstructure results are also consistent with FE analysis results.  相似文献   

12.
采用连续等通道转角挤压工艺,以连续的方式对Al-Ti-C合金进行多道次挤压,通过观察微观组织演化,探讨晶粒细化机理和力学性能变化。结果表明:连续等通道转角挤压工艺可有效细化Al-Ti-C合金微观组织,晶粒尺寸减小至1μm左右,形变诱导是变形过程中最主要的晶粒细化机制;高密度位错堆积引起Al基体和TiAl_(3)界面的裂纹以及TiAl_(3)内部的空洞产生,裂纹进一步扩展贯穿整个TiAl_(3)颗粒,最终导致第二相TiAl_(3)组织的细化,同时细小的第二相TiAl_(3)组织的钉扎机制和剪切机制促进了Al基体细化;连续等通道转角挤压1道次后,合金硬度提升最明显,与原始态相比提高59.2%;之后随挤压道次的增加,硬度提升的趋势变缓,合金塑性下降,韧性提高。  相似文献   

13.
等径角挤压对Al-Cu-Mg-Ag合金组织性能的影响   总被引:1,自引:1,他引:1  
为研究大塑形变形对耐热铝合金的作用,采用铸冶金工艺制备了新型的Al-Cu-Mg-Ag耐热铝合金,通过显微组织观察、差热分析及硬度测试等方法,研究了等径角挤压对耐热铝合金显微组织与力学性能的影响.结果表明:通过对挤压态的Al-Cu-Mg-Ag耐热铝合金在固溶淬火后时效前进行等径角挤压变形,可获得晶粒尺寸低于2μm的块体超...  相似文献   

14.
Equal channel angular pressing (ECAP) is a metal processing technique that is used to produce materials with ultrafine (<1 μm) grain sizes. In this work, the effect of the initial microstructure on ECAP of commercially pure titanium (CP Ti), a material used in many industrial applications, was investigated. To produce different initial microstructures, samples of CP Ti were exposed to different annealing conditions: no annealing (Material 1), annealed at 1033 K for 2 hr (Material 2), or annealed at 1173 K for 4 hr (Material 3). Each material was subjected to one pass of ECAP and the resulting microstructures were analyzed using XRD, SEM, and TEM, and compared to the microstructures before ECAP. It was found that each material developed a unique microstructure after one pass of ECAP, which was attributed to the varying microstructural characteristics before ECAP. Microhardness values before and after ECAP varied with each microstructure.  相似文献   

15.
电磁-悬浮铸造对变形镁合金晶粒细化的影响   总被引:1,自引:0,他引:1  
在悬浮铸造的基础上引入了电磁搅拌,并将其与悬浮铸造的优点有机结合,通过不同电磁搅拌时间对悬浮铸造AZ61变形镁合金进行了试验,悬浮剂的加入使合金液中形成了大的能量起伏和成分起伏,有助于形成细晶组织,电磁搅拌的引入加速了悬浮剂和合金母液的均匀混合,有效避免了悬浮剂在合金液中的聚集"搭桥"现象和悬浮剂在铸件中的夹生,结果表明在悬浮剂为2%(质量分数)时进行2 min搅拌时效果最佳,组织的平均晶粒度最小,达到57.5 μm,是悬浮铸造时的三分之一,是金属型铸造的四分之一.析出相Mg17Al12明显减少和细化,并且在基体上的分布更加弥散.电磁悬浮铸造(2min,2%)对比金属型铸造,抗拉强度提高了约20%,屈服强度提高了约30%,延伸率提高了近50%.  相似文献   

16.
金属材料的等通道转角挤压研究进展   总被引:3,自引:0,他引:3  
本文综述了等通道转角挤压这种新的金属材料加工及晶粒细化工艺的研究进展 ,主要包括等通道转角挤压的技术原理 ,不同工艺路线的影响 ,显微组织特性和力学性能特点等  相似文献   

17.
M.Y. Zheng  S.W. Xu  K. Wu  Y. Kojima 《Materials Letters》2007,61(22):4406-4408
Equal channel angular pressing (ECAP) has been conducted on as-cast Mg-4.3 wt.%Zn-0.7 wt.%Y Mg alloy containing quasicrystal phase at a temperature of 623 K. After 8 ECAP passes, the grain size of the as-cast alloy is decreased from ∼ 120 to ∼ 3.5 μm, and the coarse eutectic quasicrystal phases are broken and dispersed in the alloy. Tensile testing has been performed on the ECAPed Mg-Zn-Y alloy at temperatures of 523 K and 623 K with initial strain rates from 1.5 × 10− 3 to 1.5 × 10− 4 s− 1. The ECAPed alloy exhibits a maximum elongation of about 600% when testing at 623 K using an initial strain rate of 1.5 × 10− 4 s− 1. Grain boundary sliding is considered to be the dominant deformation mechanism of the Mg-Zn-Y alloy in the temperature and strain-rate range investigated.  相似文献   

18.
方晓强  李淼泉  林莺莺 《材料导报》2006,20(10):107-110,115
等通道转角挤压(equal channel angular pressing,ECAP)是一种强塑性变形技术,能有效细化材料的微观组织,提高材料性能,改善难变形材料的成形性.简述了ECAP技术制备超细晶钛合金的原理和技术现状,分析了不同工艺参数对钛合金ECAP变形过程和材料性能的影响以及晶粒细化的微观机制.  相似文献   

19.
Annealing twins are synthesised in high purity aluminium processed by dynamic equal channel angular pressing during annealing. Annealing twins and recrystallised grains encircling the twins have specific crystallographic orientation relationships with the deformed matrix grains: approximately 35°–50°<110> for the twins and 30°–45°<100> for the recrystallised grains. Stored energy during dynamic pressing, and the crystallographic orientation between annealing twins and the deformed matrix, strongly affect twin growth during annealing.  相似文献   

20.
Ultrafine-grained pure magnesium with an average grain size of 0.8 μm was produced by refining coarse-grained (980 μm) ingot by multi-pass equal channel angular pressing (ECAP) at room temperature with the application of a back pressure. The compressive deformation behaviour at room temperature depended on grain size, with deformation twinning and associated work hardening observed in coarse-grained Mg, but absent in the ultrafine grained material as decreasing grain size raised the stress for twinning above that for dislocation slip. The ultrafine grained Mg showed good plasticity with prolonged constant stress after some initial strain hardening.  相似文献   

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