共查询到20条相似文献,搜索用时 62 毫秒
1.
通过不同的加工工艺制备具有不同晶粒尺寸和织构的AZ31镁合金板材,通过室温埃里克森试验研究了工艺因素对提高镁合金板材室温成形性能的影响。结果表明:增大晶粒尺寸,减弱基面织构,可以改善镁合金轧板在变形过程中产生的在轧制方向的硬取向,增大镁合金轧板的延伸率,从而提高镁合金室温成形性能;用异步轧制工艺(轧制和退火温度为400℃、异速比为1.5)制备的试样晶粒尺寸增大到20μm、(0002)极图最大极密度仅为2,室温杯突实验测得IE值达到了5.71,显著提高了材料室温成形性能。 相似文献
2.
3.
目的 制备双峰织构类型的AZ31镁合金板,以改善板材微观组织和弱化基面织构,研究微观组织对力学性能各向异性的影响规律,以提高镁合金板材的成形性能。方法 通过弯曲限宽矫直技术对0°、30°和60°轧向切样的板材进行热加工以预制拉伸孪晶,获得双峰织构类型的AZ31镁合金板材,通过EBSD获取板材的微观组织。对RD、45°和TD方向的原始板材进行室温单向拉伸实验,获得板材的工程应力-应变曲线及力学性能参数,并计算r值(塑性应变比)与n值(应变硬化指数)。结果 弯曲限宽矫直技术可诱发大量拉伸孪晶形成ED偏转织构,将偏转织构与基面织构共存的板材称为双峰织构类型AZ31镁合金板材。拉伸孪晶的出现显著细化了晶粒,弱化了基面织构强度,使板材的屈服强度下降,极大提升了材料塑性。其中30°轧向切样的板材ND面塑性力学性能各向异性的改善效果最好,其r值最小、n值最大。结论 双峰织构类型能够弱化AZ31镁合金板材基面的织构强度,提高材料塑性。拉伸孪晶含量越高,板材的强度与塑性越好,力学性能各向异性的改善效果也越显著。 相似文献
4.
5.
通过挤压后再轧制的方法制备AZ61镁合金板材,利用动态再结晶产生局部剪切变形减弱挤压形成的{0002}基面织构,可以有效提高板材的塑性成形能力,对比分析了直接轧制75%变形量与挤轧复合轧制60%变形量的AZ61电磁半连铸镁合金板材.结果表明,两种工艺方法所得到的板材力学性能相近,前者抗拉强度σb=300 MPa,屈服强度σ0.2=230 MPa,延伸率δ=8.0%,后者σb=295 MPa,σ0.2=245 MPa,δ=8.2%.因此,可以通过挤轧复合的工艺方法利用较小的轧制变形量(60%)制备出与较大轧制变形量(75%)性能相近的镁合金板材. 相似文献
6.
7.
8.
研究了Ti60合金板材的组织、织构随热处理温度的变化规律及其对室温强度的影响。结果表明:对于Ti60合金板材,与轧制态相比,在α单相区热处理后显微组织和织构基本不变;随着热处理温度由α+β两相区升高到β单相区,等轴初生α相体积分数减少直至完全转变为片层次生α相,T型织构成分逐渐消失,并形成新的织构。在热处理温度下初生α相的体积分数,是决定是否形成新织构的主要因素:初生α相大量存在时次生α相的取向与之相近;初生α相体积分数减少对次生α相取向的影响减弱,次生α相的{0001}晶面易形成新的集中取向,与高温轧制变形后形成的β相织构有关。板材同一方向(TD或RD)的室温强度变化主要受晶内亚结构的影响:α单相区热处理后未消除晶内亚结构,板材的室温强度与轧态接近;α+β两相区和β单相区热处理消除了晶内亚结构,使强度明显降低。消除晶内亚结构后,板材相同方向的室温强度受显微组织的影响较小:初生α相体积分数的减少对室温强度没有明显的影响,在两相区不同温度热处理的板材其室温强度相当,β单相区热处理后板材的室温强度呈降低趋势,但是不同方向上的降低幅度受织构的影响较大。织构和晶内亚结构共同影响板材室温强度的各向异性,在晶体学c轴集中取向的方向上强度较高,晶内亚结构的存在弱化织构对拉伸强度各向异性的影响,在两相区和β单相区热处理消除了晶内亚结构,使板材的各向异性增强。 相似文献
9.
目的 通过显微组织表征和拉伸性能测试等方法,研究轧制温度、多道次累积压下率及轧制路径对ZK60镁合金组织演变和力学性能的影响。方法 通过在不同温度(300、340、380、420℃)与同一多道次累积压下率下进行轧制实验,明确了后续轧制实验的轧制温度。随后在同一温度、单个道次压下率为10%、不同累积压下率下进行多道次单向轧制及交叉轧制实验,并对轧制后试样的力学性能及微观组织进行分析。结果 当轧制温度为380℃、累积压下率为40.1%时,材料动态再结晶程度最大,平均晶粒尺寸减小为15.48μm,合金抗拉强度和断后伸长率最大,分别为301.46 MPa和20.56%。与多道次单向轧制相比,交叉轧制后合金板材基面织构强度明显降低,极密度值降低为9。材料RD方向的抗拉强度提高了6.35%,断后伸长率没有明显变化,TD方向的抗拉强度略微下降,但断后伸长率提高了71.47%,TD方向由脆性断裂转为韧性断裂。结论 随着温度与累积压下率的上升,ZK60镁合金的动态再结晶程度提高,晶粒得到细化,材料力学性能得到提升。在相同温度与累积压下率下,经交叉轧制后,材料基面织构显著削弱,材料的各向异性得到改善。 相似文献
10.
本文研究了汽车结构件用5754铝合金经不同冷轧变形量(冷轧率58%~75%,对应厚度2.5 mm、2.0 mm及1.5 mm)后再进行H22、H111两种退火处理的整个生产过程中组织的演化。在冷轧变形以及后续退火过程中,5754合金中等效圆直径大于0.2 μm的第二相分布不再发生改变,与热轧状态完全一致。热轧板芯部相比表层具有更多的轧制织构,存在沿厚度方向上的不均匀性。2.5 mm厚5754铝合金在冷轧和H22状态下也存在组织不均匀性。然而不同的是,冷轧后,铝合金表层轧制织构增多;在不完全退火时,这种不均匀的方式再一次发生改变,芯部依然存在大量轧制织构,而表层的再结晶程度更高,立方织构明显增多;H111状态完全再结晶退火后,板材表层和芯部组织趋于均匀。随着冷轧率的增加,2.0 mm及1.5 mm厚的板材组织较为均匀,冷轧及H22、H111退火状态板材均未出现表层与芯部的组织差异。冷轧后,板材组织呈纤维状,立方织构较热轧板进一步减少;H22不完全再结晶退火状态时,可以观察到板材发生部分再结晶,轧制织构减少,立方织构增多;至H111完全再结晶状态时,组织呈等轴晶状,立方织构达到最大值。 相似文献
11.
《International journal for numerical methods in engineering》2018,113(9):1488-1506
In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method. 相似文献
12.
Standards are the basis for production enterprises to organize production ex-factory inspection trade 《中国标准化(英文版)》2008,25(1):24-25
Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.…… 相似文献
13.
14.
Steffen Müller-Probandt 《材料科学与工程:中英文B版...》2018,(4):161-177
We associate a variety of innovations with the term "Industry 4.0". The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di... 相似文献
15.
A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa. 相似文献
16.
On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.…… 相似文献
17.
Janet Lang 《Materials and Manufacturing Processes》2017,32(7-8):857-866
ABSTRACTThe production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them. 相似文献
18.
Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß. 相似文献
19.
C. Qihong W. Zhan‐Wen J. Yi J. Yehua L. Fei F. Hanguang 《Materialwissenschaft und Werkstofftechnik》2014,45(7):582-590
In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M2(B,C), (W,Mo)2(B,C), M3(B,C), M23(B,C)6 type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm2. The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K1 mill housing of bar mill. 相似文献
20.
Dimiter Hadjistamov 《材料科学与工程:中英文B版...》2019,(2):56-65
The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ... 相似文献