固溶温度对ΦS3105合金Φ63mmx10mm冷轧管晶粒长大倾向的影响

试验用NS3105合金（/%:0.021C,0.06Si,0.02Mn,0.0007S,0.007P,29.75Cr,59.90Ni,9.88Fe,0.0100N）经12t真空感应炉熔炼,保护气氛电渣重熔成3t锭,锻造开坯Φ236mm坯,热挤压成Φ95 mm×16mm蒸管,再冷轧成Φ63mm×10mm管。研究了冷轧管800~1140℃ 5~5min固溶处理对其组织的影响。结果表明,NS3105合金热加工管经60%变形量冷轧后,合金原有的等轴晶粒发生较大变形,冷轧管变形晶粒800℃开始发生回复再结晶,950℃基本完全再结晶;随着温度提高和时间加长,冷轧管再结晶晶粒不断长大,950~1080℃时,晶粒长大不均匀,出现混晶和粗细晶条带;1080~1120℃时,晶粒长大较均匀;大于1120℃,冷轧管晶粒长大明显,组织较粗大,NS3105合金冷轧管最佳固溶处理温度为1080~1120℃。     

6063铝型材组织晶粒度控制的研究

本文讨论了影响6063铝型材组织晶粒度的因素及如何减小晶粒的的措施方法.     

变形速度及晶粒度对GH4169合金高温拉伸性能和组织的影响

研究了温度、拉伸速度、原始晶粒度对GH4169合金高温拉伸性能和组织的影响。随拉伸速度的提高，合金的强度升高，塑性下降。原始粗晶组织的强度明显高于原始细晶的相应值，而塑性则相应不同程度下降。在动态再结晶温度以上的950—980℃，原始细晶组织试样适量变形区具有均匀的10—13级晶粒。890℃、950℃和1030℃适量变形部位在正常热处理过程中晶界δ相分别呈大量聚集针状、适量短棒与小颗粒状和少量小片与薄膜状的析出特征。在热模锻条件下，选用合适的该合金细晶坯料，950℃左右的模具温度，预计锻件可获得均匀细小的晶粒和良好的晶界状态与性能。     

H68合金退火料温对其晶粒度的影响

本文对深冲用H68合金成品退火的晶粒度之影响因素进行分析,通过对原始晶粒度冷轧后（ε〉50%）的各种不同料温的晶粒度测试试验作出了不同料温情况下晶粒度的关系图,最后得出了两点结论,第一,H68合金板带的成品退火晶粒度不受原始晶粒度的影响,退火前冷加工率超过50%成品软态的晶粒度可获得最佳值;第二,H68合金板带的晶粒度与退火料温的关系是在550℃以下呈线性变化,大于550℃后变化不明显。     

用电解铝液直接生产铝材坯料的晶粒度控制

电解铝液温度在900℃左右,熔体温度过高,熔体过热。用电解铝液直接生产铝材坯料容易出现晶粒粗大。生产过程中需要适当加入固体料、控制熔炼温度和时间、添加Al-5Ti-1B杆料、控制铸造工艺等改善坯料内部组织。     

变形速度及晶粒度对GH4169合金高温拉伸性能和组织的影响

研究了温度、变形速度、原始晶粒度对GH4169合金高温拉伸性能和组织的影响.随变形速度的提高,合金的强度升高,塑性下降.原始粗晶组织的强度明显高于原始细晶组织的相应值,而塑性则有不同程度的下降.在动态再结晶温度以上的950～980℃,原始细晶组织试样的适量变形区具有均匀的10～13级晶粒.890℃、950℃和1030℃适量变形区在正常热处理后晶界δ相分别呈现大量聚集针状、适量短棒和小颗粒状以及少量小片状和薄膜状的析出特征.在热模锻条件下,选用合适的细晶坯料和950℃左右的模具温度,预计锻件可获得均匀细小的晶粒、良好的晶界状态及性能.     

微量元素对H65合金铸态晶粒尺寸的影响

以H65铸态合金为研究对象,添加不同含量的微量元素(Ti、Zr、Y、Co)。采用定性比较和定量测量的方式对合金铸态晶粒尺寸进行了分析。结果表明:Ti、Zr、Co三种元素的添加,对H65合金铸态组织可以起到细化作用;其中,以Zr元素的细化效果最为明显,添加量为0.10 %时,细化后的铸态平均晶粒直径仅为65.98 μm,是未添加时的17.3 %。     

铝合金铸轧带坯晶粒度的控制

结合生产实践,分析铸轧带坯产生粗大晶粒的主要原因,提出了铸轧带坯晶粒度的控制和细化措施。     

热连轧GH4169合金晶粒的长大规律

对热连轧GH4169合金在固溶处理过程中晶粒长大规律进行了系统的研究。研究结果表明,该合金δ相溶解温度在990~1 000℃之间,δ相对晶粒长大有显著阻碍作用,在低于δ相溶解温度进行固溶处理时,析出的δ相使得晶粒长大缓慢;在高于δ相溶解温度以上时,晶粒随温度的升高快速长大。晶粒长大动力学表明：在高于δ相固溶线温度以上进...     

Grain size and grain growth in an equiaxed alpha-beta titanium alloy

Methods of revealing grain size in a two-phase α-β titanium alloy have been examined and observations on beta grain growth in the presence of alpha have been carried out. The technique proposed by Greenfield and Margolin¹ for revealing β matrix grain sizes has been shown not to produce grain growth. However, for grain sizes of about 10 μm the G.M. technique does not reveal all the grains because of the similarity in orientation in neighboring grains. These clusters of similarly oriented grains are shown to persist as grain growth takes place but the misorientation between grains within a cluster decreases. Both the beta grain growth and alpha particle coarsening follow the same time dependency from which it is shown that a linear relationship exists between α particle size and β grain size. It is proposed that α particles must dissolve from theβ grain edges for β grain growth to occur. The linear dependency between beta grain size,D _β, and alpha particle size,d _α, can be rationalized either on the basis of geometrical or surface tension considerations. Formerly with New York University. Formerly Graduate Student with New York University.     

Control of grain size and -orientation in multi-crystalline silicon ingots

Two different cooling rates have been imposed during the early solidification of two multi-crystalline silicon ingots with 250mm diameter and 100mm height in a pilot scale directional solidification furnace. This has been done by opening a variable heat leak system below the crucible in order to achieve a high initial cooling rate in one of the ingots. The grain-structure and -orientation of these two ingots have been investigated by light microscopy (LM) and electron backscattered diffraction (EBSD), and their electrical properties by quasi-steady state photo-conductance (QSSPC) and surface photovoltage (SPV) method. The ingot with the high initial cooling rate shows predominantly grains which are significantly larger than what is usually found in mc-Si. The minority carrier diffusion lengths measured on the large grains in the ingot with high cooling rate show higher values than those measured on the ingot with smaller grains. These results indicate that principles of grain size and -orientation control in mc-Si ingots can be applied to a pilot scale furnace, and the potential for up-scaling to industrial ingots with improved electrical properties and, thus, higher solar cell conversion efficiency.     

The effect of grain size on low-cycle fatigue behavior of Al-2024 polycrystalline alloy

Two different sets of fatigue specimens were heat treated at different times or temperatures to investigate the effect of grain size on the low-cycle fatigue behavior of Al-2024 polycrystalline alloy. Strain-controlled low-cycle fatigue testing with a strain rate of 1×10⁻⁴ s⁻¹ was conducted at room temperature. The fatigue response of the alloy was evaluated macroscopically in terms of cyclic stress strain response and microscopically in terms of appearance of cyclic slip bands. The cyclic stress strain response of Al-2024 polycrystalline alloy exhibited a definite plateau region where saturation stress remained constant with plastic strain. It was found that the smaller the grain size, the lower the saturation stress and the longer the plateau, whereas the larger the grain size, the higher the saturation stress and shorter the plateau (i.e., reverse grain size effect). Microscopic observations using scanning electron microscope revealed that persistent slip bands (PSBs) were observed at 45 deg orientations from the grain boundary. The volume fraction of PSBs was higher in small-grained Al-2024 polycrystalline alloy as compared to large-grained Al-2024 polycrystalline alloy. This article is based on a presentation given in the symposium “Dynamic Deformation: Constitutive Modeling, Grain Size, and Other Effects: In Honor of Prof. Ronald W. Armstrong.” March 2–6, 2003, at the 2003 TMS/ASM Annual Meeting, San Diego, California, under the auspices of the TMS/ASM Joint Mechanical Behavior of Materials Committee.     

Effect of initial grain size of austenite on hot-deformed structure of Ni-30Fe alloy

The microstructural evolutions of Ni-30Fe alloys during hot deformation are investigated. Hot-deformed structures of Ni-30Fe alloys with initial austenite grain sizes of 20 and 140 μm are examined under various compressive strains and deformation temperatures. As the initial austenite grain size decreases, dynamic recrystallization (DRX) occurs at lower compressive strain and lower deformation temperature. At deformation temperatures where dynamic recovery occurs instead of the DRX, hot-deformed structures consist of recovered elongated grains until fine-equiaxed grains are evolved by geometric DRX. Critical compressive strain for the geometric DRX decreases with the decrease of initial austenite grain size. Geometric DRX is evolved by the impingement of serrated grain boundaries. The decrease of initial grain size is considered to reduce the critical compressive strain needed for the impingement of serrated grain boundaries. The changes in the effective thickness of austenite grain according to the compressive deformation are examined and the effects of the restoration processes on the effective thickness of austenite grain are discussed.     

初始晶粒尺寸对2024铝合金热变形行为和组织的影响

利用永磁搅拌近液相线铸造和普通铸造方法制备不同晶粒尺寸的2024铝合金铸锭,利用Gleeble-1500热模拟试验机研究初始晶粒尺寸对不同压缩变形条件下2024铝合金的热变形行为和变形后显微组织的影响。研究表明:2024铝合金的热变形行为依赖于变形条件和初始组织。初始晶粒尺寸对流变应力的影响是:当应变速率小于0.1 s~(-1)时,流变应力随晶粒尺寸减小而减少;当应变速率为10 s~(-1)时,流变应力随晶粒尺寸减小而增大。降低变形温度会弱化晶粒尺寸对流变应力的影响。热压缩流变应力随应变速率增大而增大,随变形温度升高而减小。应变速率为10 s~(-1)时,热压缩应力应变曲线呈现周期性波动;只在粗晶2024铝合金中发现变形剪切带。     

Effect of grain size on the observed pseudoelastic behavior of a Cu-Zn-Al shape memory alloy

The shape of stress-strain curves for a pseudoelastic copper-based shape memory alloy (SMA) has been found to depend strongly on the grain size-to-sample thickness ratio (gs/t). Previous investigators have attributed this effect to reduced grain constraint in coarse-grain samples. The present investigation further analyzes the grain constraint effect by modeling shape memory alloy stress-strain curves. The model results reveal that varying grain constraint can explain the observed grain size effect on stress-strain curves. Furthermore, detailed consideration of the Taylor factor equivalent for Cu-Zn-Al and NiTi shape memory alloys can explain the opposite curvature of polycrystal stress-strain curves for these two materials. Finally, several indices of grain constraint are analyzed for the Cu-Zn-Al alloy examined in the present investigation and for similar alloys used in previous studies. This evaluation reveals that both transformation modulus and transformation stress correlate with gs/t, and each can be used as an index of grain constraint.     

The effect of ingot processing treatments on the grain size and properties of Al alloy 7075

An investigation was carried out to determine the effect of various ingot thermal mechanical processing treatments on the grain size and mechanical properties of high purity homogeneous 7075 aluminum alloy sheet and plate. The results indicate that the recrystallization of 7075 alloy into a fine grained structure can be controlled by the distribution of the Cr in the microstructure, as well as by the distribution of the major alloying elements, Zn, Mg and Cu. A new ingot processing technique, FA-ITMT, was developed for producing fine grained 7075 sheet and plate. Data are presented which show that fine grained 7075 sheet and plate have equivalent strength and significantly better ductility than conventionally processed material.     

The effect of austenite grain size on microcracking in martensite of an Fe-1.22C alloy

Austenitic grain sizes of ASTM No. 9 and coarser were produced in an Fe-1.22 pct C alloy austenitized by immersion in molten lead at 1640†F (893°C), a temperature just above theA _cm for this alloy, for periods between 20 s and 1 h. Microcracking sensitivity,Sv, measured as crack area/unit volume martensite, was determined as a function of grain size in brine quenched specimens. Two locations of microcracks were observed in this investigation: 1) intragranular, resulting from the impingement of one martensite plate with another, and 2) grain boundary or intergranular resulting from the impingement of martensite plates at prior austenite grain boundaries. Intragranular microcracking sensitivity, the subject of previous investigations, increased and became the dominant type of cracking with increasing grain size, and reached a constant level for grain sizes of ASTM No. 4.5 and coarser. Total microcracking sensitivity, consisting of both intragranular and grain boundary microcracks, also increased with increasing grain size, then decreased to approach the intragranular value for grain sizes coarser than ASTM No. 3.5. On the other end of the scale, grain boundary microcracking made up a much larger proportion of the total microcracking in the fine grained specimens.     

Effects of precipitates on grain size and mechanical properties of AZ31-x% Nd magnesium alloy

The effects of precipitates on grain size and mechanical properties of as-cast AZ3 1-x%Nd magnesium alloy were investi- gated, and the affecting mechanism was also discussed. The results indicated that Al2Nd phase, AlllNd3 phase and a few AI-Mn-Nd-Fe phase were furmed when adding 0.38 wt.%-1.46 wt.% Nd into AZ31 melt, coarse AI2Nd transformed into Al11Nd3 gradually with the increasing of Nd content. Due to structure and size transformation and content increasing of AI-Nd phase, the grain size of AZ31-x% Nd alloy increased firstly, and then decreased with the increment of Nd content. After reaching a minimum value, once again it rose up, provided that Nd content was further increased. The tensile property reached its optimal value when the adding amount of Nd content was 1.05 wl.%, however, adding excessive amount of Nd deteriorated both ultimate strength and elongation ofAZ31 alloy.     

Control over grain size in memory reporting--With and without satisficing knowledge.

When answering questions from memory, respondents strategically control the precision or coarseness of their answers. This grain control process is guided by 2 countervailing aims: to be informative and to be correct. Previously, M. Goldsmith, A. Koriat, and A. Weinberg Eliezer (2002) proposed a satisficing model in which respondents provide the most precise answer that passes a minimum-confidence report criterion. Pointing to social-pragmatic considerations, the present research shows the need to incorporate a minimum-informativeness criterion as well. Unlike its predecessor, the revised, "dual-criterion" model implies a distinction between 2 theoretical knowledge states: Under moderate-to-high levels of satisficing knowledge, a grain size can be found that jointly satisfies both criteria--confidence and informativeness. In contrast, under lower levels of unsatisficing knowledge, the 2 criteria conflict--one cannot be satisfied without violating the other. In support of the model, respondents often violated the confidence criterion in deference to the informativeness criterion, particularly when answering under low knowledge, despite having full control over grain size. Results also suggest a key role for the "don't know" response which, when available, can be used preferentially to circumvent the criterion conflict. (PsycINFO Database Record (c) 2010 APA, all rights reserved)