共查询到20条相似文献,搜索用时 78 毫秒
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粉末冶金热作模具材料综合了模具钢和硬质合金各自的特点,成为一种介于模具钢和硬质合金之间的具有高强度、高耐磨及良好韧性的新型合金热作模具材料.通过热处理可改善其组织结构,达到提高性能和延长使用寿命的目的.高强高耐磨粉末冶金热作模具材料的可热处理性主要取决于基体的性质.作用于高强高耐磨粉末冶金热作模具材料基体上的热处理工艺,例如退火、淬火、回火等各种热处理工艺,可以获得满足使用性能要求的模具;同时可得出适用于高强高耐磨粉末冶金热作模具材料的最佳热处理工艺规范,提高热作模具在生产中的使用寿命. 相似文献
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通过对Ti-22Al-25Nb合金设计不同的热处理工艺路线,分别得到β/B2相和O相的两相合金及β/B2相、α2相和O相的三相合金;借助X射线衍射仪(XRD)、扫描电子显微镜(SEM)和维氏显微硬度计,研究合金在不同热处理工艺下的组织演变、物相、相含量及显微硬度。结果表明:随着热处理温度的降低,由β/B2相和O相两相组成的Ti-22Al-25Nb合金中,O相和β/B2相的晶粒尺寸都逐渐增大;O相的体积分数逐渐增加,而β/B2相的体积分数逐渐减少;合金的显微硬度逐渐增加。随着热处理温度的降低,由β/B2相、α2相和O相三相组成的Ti-22Al-25Nb合金中,α2相和O相的晶粒尺寸都逐渐增大,而β/B2相的晶粒尺寸逐渐减小;α2相和O相的体积分数逐渐增加,而β/B2相的体积分数逐渐减少;合金的显微硬度逐渐增加。这一研究结果为进一步获得综合性能优异的Ti-22Al-25Nb合金提供了数据参考。 相似文献
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《邢台学院学报》2016,(2):187-190
研究Nd/Pr含量对Nd-Fe-B合金铸锭、快淬带、退火晶化带的组织结构和磁性能的影响,得到Pr2.61Nd7.68B5.50Fe84.21、Pr2.85Nd8.36B5.44Fe83.35、Pr3.69Nd10.97B5.64Co3.94Ga0.47Fe75.29三种合金的最佳退火工艺分别为600℃/10min,700℃/10min和650℃/10min,相组成分别为2∶14∶1/α-Fe、2∶14∶1/α-Fe、2∶14∶1/富Nd相。随着Nd/Pr含量的增加,合金中2∶14∶1相含量增加,α-Fe含量降低,磁体的矫顽力增加,剩磁下降,磁能积同时受矫顽力和剩磁的共同影响,随Nd/Pr含量变化磁能积变化不大。 相似文献
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为提高硬质合金的断裂韧性,使用平均粒度分别为9.8、22.5、27.4μm的WC粉体制备3种级别(粗晶、超粗和特粗)的WC-6Co粗晶粒硬质合金,使用扫描电子显微镜和X射线衍射仪对其微观结构进行表征,并研究了WC晶粒度对粗晶粒硬质合金力学性能的影响。结果表明,随着WC平均晶粒度由粗晶(3.5~4.9μm)增加到特粗(8.0~14μm)级别,横向断裂强度和维氏硬度有所下降,但韧性得到显著改善。其中WC晶粒度为7.77μm的超粗硬质合金的横向断裂强度为(2 137.5±22.5) MPa,硬度为1 011.6 HV30,在30 kg载荷下无裂纹产生,表现出优异的断裂韧性。但是,WC晶粒度为8.83μm的特粗硬质合金的断裂韧性为13.3 MPa·m1/2,低于超粗硬质合金,这与特粗WC晶粒中的微观缺陷有关。 相似文献
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我们在长期从事工装和刀具设计与制造的工作中,常常会碰到这样的事情,如焊接刀具在焊接后未及时刃磨,也没进行分类保管,或硬质合金刀头存放较长时间后,使不同类型刀头混在一起,待要使用时,无法分辨是哪一类硬质合金而不敢使用,在这种情况下,怎样辨别YG类和YT类硬质合金呢?根据不同类硬质合金的性质,结合平时的工作经验,我认为通常可采用下列一些方法进行辨别,不妨试试看。 相似文献
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为了研究稀磁半导体Co/TiO2薄膜的微观结构和磁性,进一步探讨制备工艺和测量方法对稀磁半导体薄膜材料的影响。通过高真空对靶直流磁控溅射装置和原位退火工艺制备了Co/TiO2薄膜样品,然后利用扫描探针显微镜、振动样品磁强计和X射线衍射仪对所制得的薄膜样品的磁性和微结构进行了研究,发现磁性金属Co的掺杂量对Co/TiO2薄膜的结构及磁性有重要影响。结果表明:样品的表面粗糙度和颗粒尺寸随磁性金属含量升高而增大;随着Co百分含量的升高,形成的薄膜样品Co/TiO2和Co金属混合结构会减小矫顽力;对于Co含量较低样品其磁滞回线的斜率在低温测量时得到的结果明显小于室温环境的结果,归因于受到了顺磁相的影响。由X射线衍射结果可知此时样品为锐钛矿结构。 相似文献
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钢结硬质合金工模具的加工方法、设计特点及应用 总被引:1,自引:0,他引:1
晁拥军 《温州职业技术学院学报》2002,2(3):26-28,31
钢结硬质合金是一种特性介于钢和硬质合金之间的新型金属材料,它既有硬质合金高硬度、高耐磨性的特点,也有钢的可加工性、可锻性,可焊性,可热处理性等特点,并已在机械工业、冶金工业、地质矿山和石化工业等领域得到了应用。研究钢结硬质合金的特性并进一步推广其应用,将有利于推进材料技术及相关领域的发展,能够创造出更大的经济、社会效益。 相似文献
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热处理温度对溶胶-凝胶法制备TiO2薄膜性能的影响 总被引:1,自引:0,他引:1
采用溶胶-凝胶法在多孔钛表面制备TiO2薄膜;研究不同热处理温度对TiO2薄膜晶相结构的影响,结果显示,随着热处理温度的升高,TiO2由无定形结构向锐钛矿型和金红石型依次转变,当热处理温度达到800℃时,锐钛矿全部转变为金红石;测试分析了钛基底和不同温度热处理后的TiO2薄膜样品在0.9%NaCl生理盐水中的耐腐蚀特性,发现800℃热处理TiO2薄膜的耐腐蚀性最强。 相似文献
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《海外英语》2007,(5):10-11
Many college freshmen arrive woefully unprepared to do college work, and as disadvantaged populations continue to grow, the share of the American work force that has made it through college is expected to plummet. Many experts blame that educational failure not just on high schools but also on colleges. School & College, a special report by The Chronicle, looks at efforts to fix the system. What reforms would better prepare students for college? What should schools and colleges be doing differently? How should state and federal officials help? 相似文献
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《海外英语》2007,(4):36
There are numbers of crossroads on our long and unpredictable life journey where we totally have no idea about which direction to choose. No matter what our decision is, we should not turn back, but face the music and go ahead instead. I am this kind of girl who always does try without regretting, one example is how I dealt with my love. 相似文献
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Migration occurs behind a variety of reasons and has a great effect on the whole world. People may migrate in order to improve their economic situation, or in order to escape civil strife, persecution, and environmental disasters. The impact of migration is complex, bringing both benefits anddisadvantages. This paper briefly talks about the causes of migration, the allocation of benefits, and the ways in which individual countries and the international community deal with this important subject. 相似文献
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Sister Carrie is one of the most controversial characters in American literature.Thought as a "fallen woman" firstly,she was defined as a "new woman" by some critics later. However, by digging into the motivaton behind the whole process of Carrie's "success", the relationship between Carrie and her creator (the author), the social conditions of then American, it can be found that Carrie has never been free-standing on her thought and she has never found her real-sdf even after becoming a famous actress. In a society dominated by mass consumerism Carrie is only an adherent of her own desires. She also is a representative of all those country girls flooded into cities, a symbol and a sacrifice of the urbanization of America in a time countryside was overcome by cities. 相似文献
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RUZBEHANI Mohsen 《重庆大学学报(英文版)》2004,3(1):20-25
1.IntroductionOne-cyclecontrolmethod,whichwasproposedaboutonedecadeago[1],hasbecomeanattractivemethodinspecialfieldssuchaspowerfactorcorrection[2-6],switchingamplifiers[7,8],etc.Themainideaofthiscontrollerisbasedonintegrationofdiodevoltageinone-cycleandforcesittobeexactlyequaltothereferencevalue.Themainadvantageofthiscontrollerisitsrealtimeabilitytorejectthevariationofinputvoltage[1].Despitethisgreatability,ithasnogoodperformancesinrejectingofloaddisturbanceandfollowingreferencecommands.Espec… 相似文献
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唐芳 《读与写:教育教学刊》2008,5(6)
During interview with English majors, it was found that a majority of students expressed disappointment with their experience of English literature classes. Students' dislike of learning English literature appears to be the major problem of teaching English literature in China. Reader response approach is a good way to solve this problem. In this paper, I explain the rationale behind the reader response approach, such as its origin, definition, features, assumptions, and strategies. Then I illustrate how reader response approach works as a teaching strategy by presenting several teaching models. At last I evaluate its usefuiness for teachers and present the advantages of reader response approach in Chinese context. 相似文献