等通道转角挤压对镁锆阻尼合金组织和性能的影响

对铸态Mg-0.6%Zr合金进行了等通道转角挤压(ECAP)变形,采用光学显微镜观察了变形后合金的显微组织,并对不同温度、不同道次变形后的合金进行了显微硬度、抗拉强度及阻尼性能测定。结果表明:合金经过ECAP变形后,发生了动态再结晶,晶粒显著细化,但随挤压温度的升高发生晶粒长大;显微硬度随挤压道次的增加而增大,抗拉强度在300℃挤压6道次时达到最大值187.80 MPa;合金经400℃挤压1道次后的阻尼性能优于铸态合金的,其他条件下均低于铸态合金的。     

温度对等通道转角挤压纯钛力学性能的影响

为研究温度对等通道转角挤压(ECAP)纯钛(CP-Ti)微观结构和力学性能的影响,采用自主设计的ECAP模具在室温、300℃两种不同挤压温度下对CP-Ti(TA2)圆棒料进行1道次挤压,并观察其微观结构及对其力学性能测试。研究结果表明,ECAP 1道次后试样晶粒得到细化并且出现板条状组织和孪晶,其显微硬度和强度都有了显著地提高,而塑性有所降低。室温ECAP1道次钛试样和300℃下ECAP1道次钛试样的显微硬度和强度极限由初始的179.5 kgf·mm~(-2)、443 MPa分别增加到234.2 kgf·mm~(-2)、560 MPa和213.5 kgf·mm~(-2)、544 MPa,而断裂伸长率由初始的21.5%分别降为11.5%和16.5%。     

不同热处理工艺对7475铝合金ECAP的影响

着重研究了退火、固溶处理、双级时效以及回归热处理4种不同的热处理工艺对7475铝合金试样在ECAP变形过程中晶粒细化的影响。退火处理后的试样在不同温度和道次挤压下呈现不同的微观组织形貌，高温下退火态铝合金试样ECAP挤压后晶粒明显细化。     

等径角挤压对铸造GH696合金力学性能的影响

为了提高铸造GH696高温合金的力学性能,对该合金在1 000℃进行了等径角挤压变形,对经挤压变形及热处理后的组织与性能进行了研究。结果表明:该合金铸态组织经等径角挤压后得到了显著的细化;铸态合金经挤压变形后进行热处理时会发生再结晶;随挤压道次的增加,铸态组织的特征逐渐减少,强度和塑性得到提高;铸态合金经挤压变形和热处理后,即使还保留少量的铸态组织特征,但其强度和塑性均可达到锻态的水平。     

铸态与轧制态纯铝等径角挤压变形后的组织与性能

对铸态及轧制态的纯铝进行了等径角挤压（ECAP）变形,用透射电镜观察了变形后的显微组织,并对不同道次变形后的材料进行了硬度测定。结果表明：ECAP方法可使纯铝组织获得显著细化,在相同的变形条件下,铸态与轧制态纯铝均获得了等轴细晶组织,且晶粒尺寸相差不大。1道次ECAP变形后材料的硬度明显增大,随后每道次硬度的增大趋势明显变缓。这说明初始状态时ECAP变形后的组织和性能影响不大．     

铝-钛-硼中间合金在等径角挤压过程中的变形行为

采用等径角挤压(ECAP)技术对铝-钛-硼中间合金进行了室温挤压试验,用高温光学显微镜、扫描电镜、硬度计等分析了ECAP对合金中第二相粒子分布形态、尺寸及显微硬度的影响.结果表明:ECAP能显著改善合金中第二相粒子的分布形态,细化其尺寸;用试样绕其纵轴旋转9°.、方向不变的加工路径(Bc),经过8道次挤压后,第二相粒子由原来的散乱分布变成较为均匀分布,由原长约20μm、宽约10μm的块状粒子细化为5μm左右的小颗粒;挤压1道次后,材料硬度增加最为明显,4道次后硬度增加趋势变缓.     

等径角挤压道次对纯锡显微组织与力学性能的影响

在室温下对纯度为99.99%的锻态纯锡板进行不同道次(0～20道次)的等径角挤压(ECAP),研究ECAP道次对纯锡显微组织和力学性能的影响。结果表明：在ECAP的剧烈剪切作用下纯锡晶粒中产生孪晶,并发生孪晶诱导再结晶,晶粒显著细化,当ECAP道次超过12道次时,晶粒细化效果减弱;随着ECAP道次的增加,纯锡的织构强度和最大取向密度降低,硬度、强度和断后伸长率均增大;与锻态纯锡相比,经20道次ECAP后的硬度、屈服强度、抗拉强度和断后伸长率分别提高了9.09%,5.14%,32.08%,144.19%;当ECAP道次数少于8道次时,纯锡的主要强化机制为加工硬化,而当ECAP道次数多于8道次时,主要强化机制为细晶强化。     

不同状态Mg-9Li-3Al-2.0Gd合金的显微组织及性能

使用对掺法制备了铸态Mg-9Li-3Al-2.0Gd合金,之后对其进行挤压处理,研究了铸态和挤压态合金的显微组织、拉伸性能及耐腐蚀性能。结果表明:铸态合金主要由α-Mg、β-Li、Al3Gd和MgAlLi2相组成;经过挤压变形后,合金的组织得到明显细化,但其物相组成并没有发生变化,只是在挤压过程中发生了完全动态再结晶;挤压态合金的抗拉强度和伸长率分别达到了251MPa和20.2%,与铸态合金相比提高了39.4%和32%;铸态合金的拉伸断口表现为韧窝断裂与解理断裂的复合型断裂特征,而挤压态合金趋于微孔聚集型断裂;与铸态合金相比,挤压态合金表现出了更好的耐腐蚀性能。     

回火温度对Ti28Co14Ni37.12Zr20.88高熵合金显微组织和力学性能的影响

对铸态Ti₂₈Co₁₄Ni_37.12Zr_20.88高熵合金在不同温度(673,723 K)下进行回火热处理,研究了回火温度对高熵合金显微组织和力学性能的影响。结果表明：铸态、673 K回火态、723 K回火态合金的显微组织均由体心立方结构TiNi基体相和少量面心立方结构Ti₂Ni第二相组成;随着回火温度升高,TiNi相晶粒和Ti₂Ni相颗粒得到细化;铸态合金经过回火热处理后,其弹性极限和屈服强度增大;673 K回火态合金的抗压强度低于铸态合金,但回火温度升高至723 K后,抗压强度提升,高于铸态合金;铸态高熵合金的断裂机制以解理断裂为主,沿晶断裂和韧性断裂为辅;673 K和723 K回火态高熵合金的断裂机制以解理断裂为主,沿晶断裂为辅。     

往复挤压Mg-4Al-2Si合金时Mg_2Si颗粒的破碎规律

采用往复挤压工艺细化Mg-4Al-2Si(AS42)镁合金组织,研究了挤压过程中Mg_2Si颗粒的细化效果、破碎特征、分布规律及破碎机制。结果表明:从铸态到挤压8道次态,随挤压道次的增加,颗粒不断细化,均匀度和弥散度逐渐提高;挤压11道次时,颗粒发生粗化;合金在400℃、应变速率0.01s~(-1)条件下的压缩峰值应力约为75MPa,大于Mg_2Si颗粒的断裂应力(48MPa),挤压使颗粒发生开裂;随挤压道次的增加,位错密度逐渐增大,位错在Mg_2Si颗粒处的数量增多,应力集中急剧增大,从而导致颗粒发生破碎。     

Structure and microstructure evolution of Al–Mg–Si alloy processed by equal-channel angular pressing

An ultrafine grained Al–Mg–Si alloy was prepared by severe plastic deformation using the equal-channel angular pressing (ECAP) method. Samples were ECAPed through a die with an inner angle of Φ = 90° and outer arc of curvature of ψ = 37° from 1 to 12 ECAP passes at room temperature following route B_c. To analyze the evolution of the microstructure at increasing ECAP passes, X-ray diffraction and electron backscatter diffraction analyses were carried out. The results revealed two distinct processing regimes, namely (i) from 1 to 5 passes, the microstructure evolved from elongated grains and sub-grains to a rather equiaxed array of ultrafine grains and (ii) from 5 to 12 passes where no change in the morphology and average grain size was noticed. In the overall behavior, the boundary misorientation angle and the fraction of high-angle boundaries increase rapidly up to 5 passes and at a lower rate from 5 to 12 passes. The crystallite size decreased down to about 45 nm with the increase in deformation. The influence of deformation on precipitate evolution in the Al–Mg–Si alloy was also studied by differential scanning calorimetry. A significant decrease in the peak temperature associated to the 50% of recrystallization was observed at increasing ECAP passes.     

ZK60镁合金棒材ECAP过程有限元模拟分析

采用刚黏塑性有限元理论,在挤压温度为200℃、挤压速度为2 mm/s、背压强度为40 MPa时,对ZK60镁合金棒材进行四道次ECAP过程的数值模拟,观察棒材在四道次ECAP过程中金属流动情况,并分析棒材在四道次ECAP过程中应力场和温度场的分布和变化规律.     

Segregation of solute elements at grain boundaries in an ultrafine grained Al-Zn-Mg-Cu alloy

The solute segregation at grain boundaries (GBs) of an ultrafine grained (UFG) Al-Zn-Mg-Cu alloy processed by equal-channel angular pressing (ECAP) at 200 °C was characterised using three-dimensional atom probe. Mg and Cu segregate strongly to the grain boundaries. In contrast, Zn does not always show clear segregation and may even show depletion near the grain boundaries. Trace element Si selectively segregates at some GBs. An increase in the number of ECAP passes leads to a decrease in the grain size but an increase in solute segregation at the boundaries. The significant segregation of alloying elements at the boundaries of ultrafine-grained alloys implies that less solutes will be available in the matrix for precipitation with a decrease in the average grain size.     

等通道转角挤压对铬青铜腐蚀行为的影响

采用电化学测试和浸泡腐蚀试验研究了12道次等通道转角挤压(ECAP)处理前后铬青铜在氢氧化钠溶液中的腐蚀行为。结果表明:ECAP对铬青铜的自腐蚀电位有降低作用;挤压后铬青铜在浸泡过程中的质量损失速率高于未进行挤压粗晶铬青铜的;ECAP并未从根本上改变其电化学腐蚀机制,但却显著改变了其腐蚀形式,未挤压铬青铜的腐蚀形式为沿晶腐蚀,挤压后的腐蚀形式为均匀腐蚀。     

Effects of solution treatment and sheath on mechanical properties of Al7075 processed by ECAP

Al7075 as a hard-to-work alloy is processed difficultly by Equal channel angular pressing (ECAP) at room temperature. In this paper, experiments were conducted at several heat treatment conditions and also with a new developing strategy using sheath copper to process this alloy at room temperature. Mechanical properties were evaluated by tensile and micro hardness tests. The results demonstrated that the ultimate and yield strength of ECAPed aged samples improved. Tensile test of 4 pass processed samples with copper sheath indicated an increase in the strength in comparison with samples without sheath. The hardness test results showed more uniform distribution of hardness in their cross section for copper sheath casing samples. It was found that by increasing the copper sheath thickness, the hardness variation decreased while the average hardness increased. By considering the time limitation for the process, only solid solution samples without sheath could be successfully ECAPed in 2 passes and samples with sheath could be ECAPed only in one pass.     

铸态奥氏体-贝氏体球墨铸铁的研究

本文较系统地研究了在不同模数下,合金加入量对铸态奥氏体-贝氏体球墨铸铁的组织和性能的影响。研究结果表明,通过合金化获得铸态奥-贝球铁是可行的。它的抗拉强度可达9×10{sup}8N/m{sup}2以上,延伸率可达3%以上。并且它具有较高的低温冲击韧性,在-40℃时,冲击韧性（V型缺口）达4.6J。常温断裂韧性可达5.4×10{sup}7N/m{sup}(3/2),经325℃回火后可再提高20%,研究表明,残余奥氏体对于机械性能有良好的作用。     

Mg-12Gd-3Y-0.5Zr镁合金的显微组织、力学性能及时效析出相

通过光学显微镜、扫描电子显微镜、透射电镜、X射线衍射仪、高温拉伸试验机等对不同状态下Mg-12Gd-3Y-0.5Zr镁合金的显微组织、高温力学性能及时效析出相进行了分析。结果表明:该合金铸态组织由α-Mg固溶体、Mg5Gd析出相及α-Mg+Mg24Y5共晶体组成;挤压变形后合金的晶粒尺寸明显减小;合金挤压轧制板材在常温及150℃时有较高的抗拉强度,当温度进一步升高时强度下降较快;合金轧制板材时效析出相在高温(高于250℃)拉伸过程中没有发生相变,但在拉伸过程中会改变分布及形貌,使得变形抗力减小。     

均匀化处理对铝锌镁钪合金组织和性能的影响

采用电导率测试、室温拉伸性能测试、扫描电镜和透射电镜分析等方法,研究了不同的均匀化处理对铝锌镁钪合金组织和性能的影响。结果表明:铸态铝锌镁钪合金为过饱和固溶体,合金元素在晶界偏析,形成了富锌、镁的非平衡共晶T相和富铁、硅、锰的杂质相;当均匀化温度为350℃,过饱和基体析出平衡相η-MgZn2;随着均匀化温度的升高,非平衡共晶T相逐渐溶入基体,电导率下降,晶内析出大量Al3(Sc,Zr)粒子,合金的热加工性能提高;470℃×12h是试验合金较适宜的均匀化制度。     

铸造铝硅镁系合金钡盐变质工艺参数的确定

研究了钡盐加入量、变质温度和冷却速率等对钡盐变质铸造铝硅镁系合金组织和性能的影响。结果表明:随着钡盐加入量的增加,试验合金的变质效果越明显,但过多反而会使合金的组织和性能恶化;提高冷却速率对变质效果有利;钡盐变质最佳的温度为750℃左右,加入钡盐的最佳质量分数为1.0%;钡盐变质的长效性及重熔稳定性均很好。