Al2O3短纤维／ZA22合金复合材料凝固的方式及组织

采用扫描电镜及能谱仪等测试手段研究了挤压铸造Ａｌ２Ｏ３短纤维增强ＺＡ２２合金复合材料的凝固方式及组织特征。结果表明，在该复合材料中，短纤维呈准二维随机分布。     

ZA22／Al2O3（F）复合材料室温拉伸强度的模拟研究

采用挤压法制备ＺＡ２２／Ａｌ２Ｏ３（Ｆ）复合材料，分别采用强度混合准则和神经网络模型研究了含Ｃｅ与不含Ｃｅ的ＺＡ２２／Ａｌ２Ｏ３（Ｆ）室温拉伸强度随短纤维体积分数Ｖｆ的变化情况，结果表明：强度混合准则能有效地预测复合材料的两个重要体积分数即最小体积分数Ｖｍｉｎ和临界体积分数Ｖｃｒｉｔ；而神经网络不仅能较准确地预测Ｖｍｉｎ和Ｖｃｒｉｔ，并且能够较好地描述复合材料强度随Ｖｆ的变化规律。     

稀土La对Al-Si合金复合材料凝固组织与溶质偏析的影响

利用挤压铸造法制备了Al2O3/Al-Si-La复合材料;研究了稀土La对复合材料凝固组织以及基体合金凝固时溶质偏析的影响。结果表明,稀土La可细化基体合金的凝固组织,La富集在界面附近,有利于改善铝合金液对氧化铝短纤维的润湿性,但是未发现任何富稀土相在界面上形成。稀土La对基体合金中镁的偏聚没有明显的影响,镁和稀土La均在界面处富集,且它们的分布位置大致近似。     

铸造Al2O3／ZA4Cu3复合材料凝固组织研究

采用挤压铸造制备了Ａｌ２Ｏ３短纤维增强锌合金复合材料,研究了其凝固组织。结果表明,复合材料的组织致密,纤维分布均匀,基体组织细小;纤维与基体间存在明显的界面层,合金元素通过适当的化学反应可改善纤维与基体结合;在凝固过程中,纤维可作为锌合金共晶体非自发形核的衬底,纤维／基体界面上的硅在共晶体的共生生长过程中,起了领先相作用,导致复合材料的共晶转变是由铝硅共晶转变和锌铝共晶转变组成。     

ZA22合金半固态超塑性

对ＺＡ２２合金超塑态组织，空冷组织，淬火组织进行拉伸试验研究，结果表明，在适宜的组织，温度、形变速率条件下，ＺＡ２２合金具有半固态超塑性，此时应变速率敏感系数ｍ值为０．４９，晶界微熔为超塑性产生创造了有利的条件。     

硅酸铝短纤维增强Al-12Si合金复合材料的磨损行为

用挤压铸造法制备了低体积分数（３％～７％）的硅酸铝短纤维增强Ａｌ１２Ｓｉ合金复合材料,并利用销盘磨损试验机研究了材料在干摩擦条件下的磨损行为。磨损试验结果表明：硅酸铝短纤维加入到Ａｌ１２Ｓｉ合金明显提高抗磨损能力,随纤维体积分数的增加该复合材料的耐磨性逐渐增强。金相观察和测试表明：基体合金和复合材料的磨损区由硬化层和变形层组成,断裂的ＡｌＳｉ共晶相沿滑动方向重新分布排列形成了硬化层;而复合材料硬化层由于破断的硅酸铝纤维和破碎的ＡｌＳｉ共晶相的共同作用,使该硬化层硬度高于基体合金硬化层的硬度,从而使复合材料表现出优异的耐磨性。并根据试验结果提出了基体合金和复合材料的磨损机制模型     

挤压铸造莫来石短纤维增强Al—4.5Cu复合材料的凝固组织,偏析及性能的研究

本文研究了凝固冷却速度对挤压铸造莫来石短纤维增强Ａｌ４５Ｃｕ复合材料的凝固组织和显微偏析的影响。结果表明：αＡｌ相在短纤维间隙中形核并向纤维表面生长，θＣｕＡｌ２相以莫来石短纤维为基底非均质形核；随凝固冷却速度的减慢，θＣｕＡｌ２相析出量增多且由蠕虫状向块状转变，纤维表面的Ｃｕ浓度增大，纤维间隙中Ｃｕ浓度减小，即Ｃｕ元素的显微偏析增大，复合材料的抗弯强度降低。     

挤压铸造工艺参数对Al_2O_(3f)/Al-4.5%Cu复合材料凝固方式与组织的影响

挤压铸造制备了Al2O3短纤维/Al 4 5%Cu合金复合材料,研究了关键工艺参数对基体合金凝固方式与组织的影响。结果表明:Al2O3短纤维表面不能作为基体α初晶非自发形核衬底;随凝固冷却速度ε的增大,复合材料基体组织将细化,基体中有更多完整的晶界出现,偏析第二相主要分布于晶界上,其量随ε的增大而明显增多;纤维体积分数Vf的增大将细化基体晶粒尺寸至纤维间隙大小,同时随Vf的增大,主要分布于纤维/基体界面的偏析第二相的量将有所降低;模具、预制块预热温度及合金液浇注温度对复合材料凝固过程的影响归结到对凝固冷却速度的影响上来;外加压力的提高使复合材料基体组织细化。     

硅酸铝/铝硅合金梯度复合材料的研究

采用挤压铸造技术制备硅酸铝短纤维增强铝硅合金梯度复合材料，研究了这类材料的凝固组织和基本热物理性能。结果表明，在复合材料中，基体组织细小，纤维与基体结合良好，并呈梯度状无序分布；梯度复合材料的热物理性能优异。     

非连续增强铝硅合金复合材料的凝固组织与断口形貌

用扫描电子显微镜(SEM)观察和研究了氧化铝短纤维增强铝硅合金复合材料的凝固组织和断口形貌。结果表明，在复合材料中纤维分布均匀，氧化铝纤维可作为硅相非自发形核的衬底；氧化铝纤维与铝合金基体之间的界面对材料性能影响很大。改善制备工艺应从控制界面反应和细化组织入手。     

氧化铝纤维对锌合金复合材料凝固组织的影响

利用挤压铸造制备了氧化铝纤维增强锌合金复合材料，研究了氧化铝纤维对锌合金复合材料凝固组织的影响。结果表明，在复合材料中，纤维与基体间存在致密界面层，合金元素通过适当的化学反应可改善纤维与基体的结合；在凝固过程中，氧化铝纤维可作为锌合金共晶体非自发形核的衬底，纤维／基体界面上的硅在共晶体的共生生长过程中起了领先相作用，导致复合材料的共晶转变由铝硅共晶转变和锌铝共晶转变两者组成     

氧化铝短纤维增强锌合金复合材料的凝固组织与界面

利用挤压铸造制备了氧化铝短纤维增强锌合金复合材料，研究了其凝固组织与界面。结果表明，复合材料的组织致密，纤维分布均匀，基体组织细小；纤维与基体间存在明显的界面层，合金元素通过适当的化学反应可改善纤维与基体的结合；在凝固过程中，氧化铝纤维可作为锌合金共晶体非自发形核的衬底，纤维／基体界面上的硅在共晶体的共生生长过程中起了领先相作用，导致复合材料的共晶转变是由铝硅共晶转变和锌铝共品转变两者组成。     

Rheocasting Al Matrix Composites

Aluminum alloy matrix composites reinforced by SiC short fibers (or whiskers) can be prepared by rheocasting, a process which consists of the incorporation and homogeneous distribution of the reinforcement by stirring within a semi-solid alloy. Using this technique, composites containing fiber volume fractions in the range of 8–15%, have been obtained for various fibers lengths (i.e., 1 mm, 3 mm and 6 mm for SiC fibers). This paper attempts to delineate the best compocasting conditions for aluminum matrix composites reinforced by short SiC (e.g Nicalon) or SiC whiskers (e.g., Tokamax) and characterize the resulting microstructures.     

Aging characteristics of short glass fiber reinforced ZA-27 alloy composite materials

Aging characteristics of short glass fiber reinforced ZA-27 alloy composite materials have been evaluated in the present study. The liquid metallurgy technique was used to fabricate the composites, in which preheated short glass fibers were introduced into the ZA-27 alloy melt above its liquidus temperature. The aging temperature employed was 125 °C for 6, 12,18, and 24 h. The aged alloy (no fibers) reached the peak hardness after 18 h, while the composites (regardless of filler content) reached the same hardness in 12 h. It is hypothesized that the aging treatment of a composite improves the strength of the interface between the short fibers and the matrix. This is confirmed by the tensile fractograph analysis, which indicates that at a given aging temperature, the composites aged for 18 h exhibit short fibers that remain attached to the metal matrix, while those aged for 6 h undergo debonding.     

CeO2在镀镍碳纤维增强铝合金基复合材料中的作用

以稀土氧化物CeO2为添加剂,研究CeO2对镀镍碳纤维增强铝合金基复合材料碳纤维的分布、气孔率以及力学性能的影响,利用扫描电镜分析和拉伸力学性能检测等探讨了CeO2在镀镍碳纤维增强铝合金基复合材料中的行为。结果表明:CeO2能够使碳纤维均匀分布在复合材料中,而不产生分层及团聚;而且能够降低复合材料的气孔率,使轧制态复合材料的抗拉强度、屈服强度分别提高23%和26%。     

Effect of Mg-based spherical quasicrystal on microstructures and mechanical properties of ZA54 alloy

To improve the strength,toughness and heat-resistance of magnesium alloy,the microstructure and mechanical properties of ZA54 alloy reinforced by icosahedral quasicrystal phase(I-phase) particles were studied.Exceptα-Mg,φ-phase andτ-phase,MgZnYMn I-phase particles can be obtained in ZA54-based composites by the addition of icosahedral quasicrystal-contained Mg-Zn-Y-Mn master alloy.The introduction of MgZnYMn I-phase into ZA54 alloy has great contribution to the refinement of matrix microstructures and the improvement of mechanical properties.When the addition of Mg-based spherical quasicrystal master alloy is up to 3.5%(mass fraction) ,the macro-hardness of ZA54-based composites is increased to HB 68.The impact toughness of composites reaches the peak value of 18.3 J/cm2,which is about 29%higher than that of ZA54 mother alloy.The highest tensile properties at ambient and elevated temperatures with master alloy addition of 2.5%(473 K) are also obtained in ZA54-based composites with 3.5%(mass fraction) Mg-Zn-Y-Mn master alloy addition.The ultimate tensile strength of composites at ambient and elevated temperatures are 192.5 MPa and 174 MPa,which are 23.4%and 33.8%higher than that of ZA54 mother alloy,respectively. The improved mechanical properties are mainly attributed to the pinning effect of I-phase on grain boundaries.     

MICROSTRUCTURE ANALYSIS AND MECHANICAL PROPERTIES OF Zn—Al ALLOY ROD PRODUCED BY HEATED MOLD CONTINUOUS CASTING

The new technology of continuous casting by heated mold was used to produce directional solidification ZA alloy lines to eliminate the inter defects of these lines and increase their mechanical properties. The results are as follows: (1) The microstruc-ture of the ZA alloy lines is the parallel directional dendritic columnar crystal. Every dendritic crystal of eutectic alloy ZA5 was composed of many layer eutectic β and η phases. The micro structure of hypereutectic ZA alloys is primary dendritic crystal and interdendritic eutectic structure. The primary phase of ZA8 and ZA12 is β, among them, but the primary phase of ZA22 and ZA27 is a. (2) Through the test to the as-cast ZA alloy lines made in continuous casting by heated mold, it is found that the tensile strength and hardness increase greatly, but the elongation decreases. With the increase of aluminum amount from ZA 5 to ZA 12, ZA22 and ZA27, the tensile strength increases gradually. ZA27 has the best comprehensive mechanical properties in these     

纤维增强金属基复合材料耐磨机制的研究

根据纤维增强金属基复合材料的结构特点，研究了界面在复合材料磨损过程中的作用，磨损时，复合材料的界面可消耗纹扩展能量，阻滞裂纹扩展，氧化铝短纤维增强硅合金合材料具有优异的耐磨性；基体中的合金元素有利于形成良好的界面，改善复合材料的耐磨性。