共查询到18条相似文献,搜索用时 140 毫秒
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泡沫铝合金制备工艺研究 总被引:6,自引:1,他引:5
采用正交实验方法,选择三种不同粒径的填料,系统研究了粒子预热温度、金属液浇注温度和充型压力对渗流铸造泡沫铝合金成型工艺的影响,并对试验结果作了理论分析。认为,合理选择粒子预热温度是生产泡沫金属铸件的前提,适当提高浇注温度是保证泡沫组织均匀良好的关键,保持适度的充型压力有利于提高材质通孔率和工艺的稳定性。 相似文献
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一种多孔铝合金制备技术的研究 总被引:1,自引:0,他引:1
采用加压铸造法制备出多孔铝合金大块试样,系统地研究了浇注温度,充型压力等工艺参数对充型过程的影响。实验表明,预制块的初始预热温度对最终制品的有效长度起着重要作用,高的浇注温度及较大的充型压力也有助于金属液向空隙的渗透。 相似文献
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用低压渗流法制备泡沫铝合金 总被引:16,自引:0,他引:16
用低压渗流法生产泡沫铝合金,研究了影响液体金属渗流高度的工艺参数,实验表明,渗流高度随着颗粒的预热温度,外加渗流压力和铝液浇注温度的升高而增加,其中颗粒预热温度的影响最为显著,其他因素的影响不大,实验还表明,颗粒尺寸对于降低渗流高度起了重要作用,颗粒尺寸越小,渗流高度越低,对于不同尺寸的颗粒,都存在一个临界预热温度。 相似文献
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多孔铝合金的铸造工艺研究 总被引:6,自引:0,他引:6
采用加压铸造工艺,制备出了多孔铝合金。系统地研究了预制块的制备工艺过程及影响因素。利用所制备的预制块,研究了多孔铝合金的加压铸造工艺。研究表明,预制块孔隙大小及其初始温度、金属液浇注温度、外加压力等影响了金属液在预制块中的充型长度。采用合理的工艺,就可以获得大尺寸的多孔制品。 相似文献
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铝(镁)合金消失模铸造近净成形技术研究进展 总被引:2,自引:0,他引:2
阐述了铝(镁)合金消失模铸造技术的研究现状,着重介绍了铝(镁)合金消失模铸造在金属液充型、振动凝固、压力凝固以及消失模壳型铸造等技术方面的最新研究进展。研究表明,铝(镁)合金在消失模铸造过程中,需重点解决针孔、缩松等缺陷,提高液态合金的充型能力和铸件的力学性能;通过采用振动凝固和压力凝固的手段,可以提高金属液充型能力、细化组织、提高组织致密性,明显提高铸件力学性能。真空低压消失模壳型铸造技术,可以解决普通消失模铸造易于出现的孔洞和夹杂等缺陷以及浇不足和浇注温度高等问题,是一种生产复杂薄壁高质量铝、镁合金精密铸件的新方法。 相似文献
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差压铸造薄壁铝硅合金铸件的位置效应 总被引:1,自引:0,他引:1
采用差压铸造工艺,研究垂直缝隙式浇注系统浇注的铝合金硅铸件不同位置的组织和力学性能变化.采用石英砂型、SiC砂型和冷铁,浇口处铸件的晶粒最细小,致密度高、力学性能最好;铸件冷端的组织和性能次之;位于两者之间的铸件的组织和性能最差.分析表明对于具有垂直缝隙式浇注系统,差压铸造凝固压力对金属的凝固作用具有位置效应,浇口处液态金属温度高,凝固时间长,凝固压力对浇口处金属的凝固作用显著;铸件冷端金属凝固时间短,凝固压力对该处金属的凝固作用不显著,铸型的冷却速度对铸件组织和性能的影响起显著作用.浇口处与冷端之间的金属液体的凝固受压力和冷却速度的影响小,铸件的晶粒尺寸最大、密度最小、性能最低.冷却速度提高,铸件的任意位置的组织和性能都相应得到提高. 相似文献
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《Advanced Powder Technology》2007,18(4):467-483
The rates of alkoxylation and rehydroxylation reactions were investigated on silica surfaces preheated at various temperatures. The effect of preheating temperature was examined for both reactions. The initial rate of reaction was analyzed and discussed as a representative reactivity of the silica surface. For the alkoxylation reaction, the apparent rate of reactions on the total active sites was analyzed by measuring the alkoxyl groups formed on the surface. The rate of the alkoxylation reaction increased with the preheating temperature, which could be attributed to the increase in the number of reactive siloxane bridges. It was shown that the preheating treatment caused the compensation effect for the surface alkoxylation reactions. An analysis for the state of the activated complex in the reaction was proposed to discuss the kinetic characteristics. For the rehydroxylation reaction, the rate of reaction forming hydroxyls from siloxane bridges was measured. The rate of rehydroxylation decreased with increasing the preheating temperature. For both the alkoxylation and rehydroxylation, the reactivity of siloxane bridges decreased with increasing the preheating temperature. 相似文献
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基板预热可以显著降低激光金属沉积成形(laser metal deposition shaping, LMDS)过程的热应力,从而抑制成形过程裂缝的产生,但基板预热温度的高低对成形零件的微观组织有着重要的影响,因此研究不同基板预热温度下激光金属沉积成形零件的微观组织变化规律对基板预热温度的选择具有非常重要的意义.利用中国科学院沈阳自动化研究所自行研制的激光金属沉积成形系统和基板预热系统,采用Ni60A金属粉末在基板未预热和预热到200,300,400,500和600 ℃时分别进行成形试验.然后利用扫描电子显微镜和能量散射谱仪对成形试件的微观组织进行深入的研究,得到不同基板预热温度对激光金属沉积成形零件微观组织的影响规律,为基板预热温度的优化选择提供了重要参考. 相似文献
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采用毛细管流变仪和自制小型模具,对不同质量分数的短切碳纤维增强尼龙66(CF/PA66)复合材料颗粒进行了熔体流动性能分析和注塑成型工艺模拟,实现少量原料快速模拟CF/PA66的注塑成型工艺参数。研究表明:短切CF/PA66复合材料的熔体属于幂律流体,熔体黏度随温度、压力和CF质量分数变化显著,当温度和压力升高到临界值后熔体流变特性从假塑性区进入牛顿区;随着CF质量分数的增加,CF/PA66复合材料适宜成型温度提高。实验中PA66、CF质量分数为10wt%和20wt%的CF/PA66三种颗粒的适宜成型温度分别为278~285℃、280~287℃、290~298℃,通过对熔体进行Bagley压力校正,三种颗粒适宜成型的最小注塑压力分别为24.3MPa、29.4MPa、35.1MPa;将流变仪模拟所得参数应用于注塑成型工艺,所得样品的拉伸强度与流变仪制备的试样非常接近,进一步说明了毛细管流变仪模拟CF/PA66注塑成型过程的可行性和有效性,为其注塑成型工艺条件提供了理论依据。 相似文献
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The interfacial heat transfer coefficient (IHTC) shows the heat transfer capacity at the billet/die interface during the hot forming process, which affects the temperature gradient in the die that may potentially induce high thermal stress. Consequently, this determines the service life of the die. In this paper, a set of experimental equipments were used to identify the IHTC and the upsetting test of superalloy Inconel718 (GH4169) was carried out on the hot flat die to evaluate the IHTC characteristics after the billet heating and die preheating temperature, holding time, and billet deformation rate. The results indicated that the billet heating temperature has a minimal role in IHTC but the other components have a great impact on IHTC. Among them, the billet deformation rate has influenced the IHTC the most. In the die preheating temperature ranging from \(150\,^{\circ }\hbox {C}~\hbox {to}~400\,^{\circ }\hbox {C}\), it was found that the preheating temperature was proportional to IHTC. A high preheating temperature that leads to a high IHTC was found unfavorable in relieving the die surface thermal stress, and also weakened the die hardness and strength. The IHTC declined with the increase in the holding time as a result of the billet oxidation. Based on these findings, the composite ceramic and polymetallic heat-resistant coatings on the die surface were prepared, respectively, to relieve the thermal stress of die surface by reducing IHTC. It showed that both of the treated dies could effectively reduce the IHTC, blocking the transferred heat from the hot billet and making it applicable to the different hot forging events. 相似文献
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Graphitic foam is obtained from coal tar based mesophase pitch in high pressure and temperature chamber. SEM and WAXD are used to study the influence of the properties of material and foaming process on the morphology and crystal structure of graphitic foam. The results show that the mesophase pitch with softened point of 300-350 °C and mesophase content of > 80% can produce homogenous and perfect pore structure. The porosity and opening of resulted foam vary from 55% to 75% and 75% to 85% respectively. The porosity and opening decrease with the increase of pressure and increase slightly with the increase of soaking time. The graphitization degree of foam reaches to 84.9% and the ligament of graphitic foam exhibits high alignment. 相似文献