共查询到20条相似文献，搜索用时 500 毫秒
1.
何燕 《鞍山师范学院学报》2009,11(6):23-25
采用元胞自动机方法对多晶金属热变形中的动态再结晶过程建立了二维模型．模型模拟了热加工变形中动态再结晶过程．通过模拟可以得到热变形金属的微观组织形貌和变形后晶粒的大小与分布,再现了再结晶组织的微观特征．结果与实验观察到的热变形组织形貌基本符合,并分析了热加工参数对再结晶组织形貌的影响． 相似文献
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搅拌摩擦焊接（FSW）利用摩擦产生的热量将工件连接起来，而不熔化金属，是一种固态连接技术。采用FSW技术可避免传统熔化焊接产生的缺陷问题，文章从微观组织、力学性能、腐蚀性能等方面综述了钢铁材料FSW研究进展。FSW已成功应用于钢铁材料，并可获得成形性较好的接头。FSW后接头发生动态或静态再结晶，造成接头组织的演变，不仅能细化、均匀化、致密化组织、还能引起相变和晶粒取向的变化。通过控制FSW参数可获得具有良好力学性能和腐蚀性能的接头。 相似文献
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用动态热模拟试验技术，对经高效熔体综合处理的高成形性易拉罐用铝材进行高温等温压缩变形试验，并用OM、TEM观察分析了该材料在热变形过程中微观组织特征。结果表明，变形温度和应变速率对该铝材微观组织特征均有显著影响。变形温度低时，仅发生动态曰复，而当变形温度高于400℃时，发生了完全动态再结晶，可获得等轴均匀的晶粒；在较低和高的应变速率条件下。均发生了完全动态再结晶，但这两种条件下存在不同的再结晶机理，而应变速率为1．0s^-1和5．0s^-1时，仅发生动态回复；变形量较小时，显微组织变化不明显，变形量增大后，发生完全动态再结晶，若继续增大变形量，则晶粒组织将被拉长。 相似文献
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本文采用组织观察与拉伸力学试验等手段，研究了两种不同制备工艺生产的Ti-56．1wt％Ni形状记忆合金板材的杂质分布形态、热轧组织的再结晶过程、力学性能与断裂行为及其影响因素。结果表明：NiTiSMA板材原始热轧态组织中，晶粒和杂质相在轧制方向被拉长，杂质含量高的NiTiSMA板材还存在大块的脆性杂质。经1023K／1h退火处理后，NiTiSMA板材拉伸断裂过程具有应力诱发马氏体相变和马氏体自身滑移两个塑性变形阶段，拉伸断裂后组织中有马氏体残余。普通板材横向延伸率及强度与纵向无明显差异；杂质含量高的板材出现两次断裂现象，其最终断裂强度比普通板材高，但塑性差；杂质含量高的板材的横向延伸率与纵向相近，但横向强度要优于纵向。普通板材断裂机制为微孔聚集型延性断裂，而杂质含量高的板材具有解理型脆性断裂和微孔聚集型延性断裂的混合特征。 相似文献
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为了揭示HPS485wf钢动态再结晶组织演变行为,在不同的单道次热压缩变形条件下,进行了该钢动态再结晶过程的CA仿真．结果表明：随着变形温度升高,动态再结晶的孕育期缩短、速度加快,平均晶粒尺寸增加;随着应变速率加快,动态再结晶的孕育期延长、速度减慢,平均晶粒尺寸减小． 相似文献
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洪丽华 《福建工程学院学报》2007,5(3):218-221
分析了黄铜锭的冶金质量对低压铸造水暖制件组织与力学性能的影响,结果表明铜锭冶金质量直接影响铸件的杂气含量与力学性能,对于不同冶金质量的铜锭(A、B),当成分相近时,经细化处理后铸件的结晶组织形态差别不大,夹杂相均为以PbO2为主、混有CuO2、ZnO或SiO2的氧化物复合夹杂,但铸件BC的夹气较多;在相同的熔体处理及成型工艺条件下,铸件AC的抗拉强度比Bc增加了16.3%,伸长率增加了26.6%. 相似文献
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本文分别采用普通金属型铸造、电磁搅拌、半固态挤压方法制备铝铁合金,通过扫描电镜、透射电镜和力学性能测试等手段分析了不同成型方法后合金的性能和组织。结果表明,铝铁合金经过半固态成型后组织被细化,力学性能得到大幅度提高,抗拉强度由普通金属型铸造时的160MPa提高到了271MPa。 相似文献
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对几种冲压模具用的进口高强度螺栓的成分、组织、加工工艺和力学性能进行了研究。蛄果表明,几种进口螺栓材料为含有Cr、Ni等舍金元素的中碳低合金钢。热处理工艺为调质处理,碳化物颗粒非常细小均匀。拉伸断口扫描电镜观察分析表明，断口微现形貌特征为较深的韧窝。力学性能测试结果表明,进口螺栓的抗拉强度在1000MPa以上，硬度在HRC40附近。根据解剖分析结果。选择了三种国产材料45号钢、40Cr和42CrMo钢，采用调质、淬火和中温回火、等温淬火三种热处理工艺。然后对其组织和性能及微观组织进行测定，结果表明，40Cr和42CrMo经850℃油淬和450℃回火后的组织和性能与进口螺栓材料基本相同。 相似文献
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采用金相组织观察、常温和低温力学性能测试的方法,研究了回火温度对X21Cr Mo V121钢显微组织和低温力学性能的影响。结果表明,不同温度的回火热处理后,微观组织均为回火索氏体;随着回火温度的升高,材料的冲击韧性呈上升趋势,而强度及硬度逐渐下降。为了获得较好的低温冲击韧性,此类钢较好的热处理工艺应为1 050℃加热保温1 h淬火后,在720℃加热保温2 h空冷。 相似文献
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罗艳萍 《读与写:教育教学刊》2008,5(6)
The communication of people partially is the communication of cultures. Culture has a direct effect on international commercial activities in all aspects. Different conceptions about time, space, equality, law and the like, lead people to deal with things in different ways. So to know cultures of the counterpart is to facil-itate our enterprises so as to have a smooth and successful communication in commercial activity. 相似文献
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Richard Denner 《海外英语》2007,(4):14-15
Rosco and I wait for the fishermen to return.I sit at a wooden bench near the store at Mt.Baker Resort and watch the clouds change shape. Rosco has my belt around his neck and an eight foot tow chain hooked to a tree. Dogs must be on a leash. Ducks and rabbits are loose. 相似文献
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Given a graph G,a subgraph C is called a clique of G if C is a complete subgraph of G maximal under inclusion and |C|≥2. A clique-transversal set S of G is a set of vertices of G such that S meets all cliques of G. The clique-transversal number, denoted as TC (G), is the minimum cardinality of a clique-transversal set in G. The clique-graph of G, denoted as K (G), is the graph obtained by taking the cliques of G as vertices, and two vertices are adjacent if and only if the corresponding cliques in G have nonempty intersection. Let F be a class of graphs G such that F={G|K(G) is a tree}. In this paper the graphs in F having independent clique-transversal sets are shown and thus TC (G)/|G|≤1/2 for all G ∈ F. 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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陈美曦 《山东教育学院学报》2008,23(2):103-107
Different nations have different social cultures, and the social culture of every nation is developing with the development of the nation, language is greatly influenced by social culture, which enables language to possess national and historical characteristics. Word is the smallest, independent, meaningful linguistic unit of language. It can well reflect the national and historical characteristics. From synchronic aspect, the social and cultural influence on word meaning is mainly embodied in conceptual and associative meanings of word. The incorrespondence of word meaning is a phenomenon that exists in both conceptual and associative meanings of word among different languages. From diachronic aspect, the development of social culture causes some changes of word meaning to some extent. Therefore, social culture plays a key role in vocabulary learning and mastery of a language. 相似文献
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邱崇丙 《唐山师范学院学报》2014,(1):21-23
汉字的六书,《说文》对“转注”一类,语焉不详。后世学者提及转注,也仅限于许慎所举出的例字。《汉字例说》一文,作者从转注的角度综合考虑,对部分现代常用字作了分析,跟传统的解释有所不同。希望能抛砖引玉,互相切磋,以推进学术研究。 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