Al-Si/Al_2O_3 in situ composite prepared by displacement reaction of CuO/Al system

Al2O3 particle-reinforced ZL109 composite was prepared by in situ reaction between CuO and Al2O3 . The microstructure was observed by means of OM, SEM and TEM. The Al2O3 particles in sub-micron sizes distribute uniformly in the matrix, and the Cu displaced from the in situ reaction forms net-like alloy phases with other alloy elements. The hardness and the tensile strength of the composites at room temperature have a slight increase as compared to that of the matrix. However, the tensile strength at 350℃ has reached 90.23 MPa, or 16.92 MPa higher than that of the matrix. The mechanism of the reaction in the CuO/AI system was studied by using of differential scanning calorimetry（DSC） and thermodynamic calculation. The reaction between CuO and Al involves two steps. First, CuO reacts with Al to form Cu20 and Al2O3 at the melting temperature of the matrix alloy, and second, Cu20 reacts with Al to form Cu and Al2O3 at a higher temperature. At ZL109 casting temperature of 750- 780 ℃, the second step can also take place because of the effect of exothermic reaction of the first step.

Research on development of in situ titanium matrix composites and in situ reaction thermodynamics of the reaction systems

The in situ synthesis method for titanium matrix composites （TMCs） has obvious technical and economical advantages over other traditional methods. Ultrafine reinforcement particles were formed in situ by chemical reaction between elements or between elements and compounds. Using the approach, contamination at the composite matrix/reinforcement particle interface did not occur, interface bonding was good, and the reinforcement particle was thermodynamically stable. The stage of development of the preparation process for in situ TMCs as well as the thermodynamic analysis of the possible in situ reaction systems was described.

In-Situ Synthesis of AlN Powders and Composite AlN Powders with Yttrium Addition

Using Al Mg and Al Mg Y alloys as raw materials and nitrogen as gas reactants, AlN powders and composite AlN powders by in situ synthesis method were prepared. AlN lumps prepared by the nitriding of Al Mg and Al Mg Y alloys have porous microstructure, which is favorable for pulverization. They have high purity, containing 1.23%(mass fraction) oxygen impurity, and consisted of AlN single phase. The average particle size of AlN powders is 6.78 μm. Composite AlN powders consist of AlN phases and rare earth oxide Y 2O 3 phase. The distribution of particle size of AlN powders shows two peaks. In view of packing factor, AlN powders with such size distribution can easily be sintered to high density.

Microstructure and properties of in situ A356/TiB_2 composite

In situ A356/TiB2 composites were successfully fabricated via in-melt reaction among aluminium alloy, K2TiF6 and KBF4 compounds. The composite was examined by using XRD, SEM and EDX techniques. The experimental results reveal that TiB2 are dispersed homogeneously into the aluminium alloy matrix. The mechanical properties of the composites increase significantly with the addition of reinforcement, and the tensile fractography of the composite exhibits to be ductile though the elongation of the composites decreases compared with the unreinforced matrix alloy.

Reaction Mechanisms and Tensile Properties of the Composites Fabricated by Al-B2O3 System

The aluminum matrix composites(AlB2+a-Al2O3)/Al were fabricated by in situ reaction synthesis from an Al-B2 O3 system. The reaction pathways, apparent activation energies and tensile properties were analyzed by using differential scanning calorimetry(DSC), X-ray diffraction(XRD), scanning electron microscopy(SEM), and equipped energy dispersive spectroscopy(EDS). The results showed that there are two-step reactions in the Al-B2 O3 system. The first-step is 15 Al+7 B2 O3→7 aAl2O3+AlB12+2 B and the second-step is 2 B+AlB12+6 Al→7 AlB2. Their corresponding apparent activation energies are 352 and 444 kJ/mol, respectively. The tensile strength and elongation rate of the composites are 190.5 MPa and 6.6%, respectively.Compared with ordinary aluminum base material, the performance is superior. There are many dimple and cracked a-Al2O3 reinforcements in tensile fracture surface layer.

Microstructure and mechanical properties of in situ(TiC+SiC)/FeCrCoNi high entropy alloy matrix composites

In situ(TiC+SiC)particles(5 vol.%and 10 vol.%,respectively)-reinforced FeCrCoNi high entropy alloy matrix composites were fabricated via vacuum inductive melting method,with equal volume fractions of TiC and SiC particles.X-ray diffraction,scanning electron microscope and energy diffraction spectrum were employed to analyze the microstructure and composi-tion of the samples.The results manifested that the FeCrCoNi matrix is composed of FCC phase,and the in situ particles are homogeneously scattered in the matrix.The presence of reinforcements augmented the ultimate tensile strength from 452 to 783 MPa,and raised the yield strength from 162 to 466 MPa at room temperature,whereas the elongation to fracture was reduced from 70.6%to 28.6%.All the tensile fracture surfaces consisted of numerous tiny dimples,indicating that the composites exhibited ductile fracture.Furthermore,the enhancement of strength ascribes to a combination of thermal mis-match strengthening,load-bearing effect,grain refinement,Orowan strengthening and solid solution strengthening effect,which contribute about 58.0%,2.4%,12.3%,11.1%and 16.2%to the improvement of yield tensile strength,respectively.

NiAl合金锥筒内压胀形–原位反应一体化成形工艺研究

针对NiAl合金板坯制备及复杂薄壁构件二次成形困难的技术难题,提出一种成形与原位反应一体化成形新工艺制造NiAl合金薄壳件,即先将Ni箔与Al箔交替堆叠置于模具中,再在固体颗粒介质作用下塑性成形,然后使成形后的Ni/Al叠层薄壳件继续停留在模具中,在固体颗粒介质压力作用下加热使Ni/Al叠层发生原位反应合成NiAl合金,从而制得NiAl合金薄壳件。采用扫描电子显微镜(SEM)与能谱仪(EDS)对构件微观组织进行表征,并对其高温力学性能进行测试。结果表明,采用该方法制得的NiAl合金锥筒由单一NiAl相构成,厚度方向上粗晶层与细晶层交替排布,为典型的双峰组织,无孔洞等缺陷。构件硬度为317HV且分布均匀,1000℃抗拉强度为71MPa,延伸率可达74%。

免热处理(TiB_(2)+ZrB_(2))/Al-Mg-Mn基复合材料的显微组织与力学性能

基于交通、航空航天等领域高强韧精密复杂零件免热处理的需求,采用原位生成反应法制备了(TiB_(2)+ZrB_(2))/Al-Mg-Mn基复合材料,对比研究了重力铸造和挤压铸造制备的(TiB_(2)+ZrB_(2))/Al-Mg-Mn基复合材料的微观组织和力学性能。结果表明:原位生成反应法制备的复合材料中生成了大量纳米级的TiB_(2)和ZrB_(2)颗粒。拉伸实验结果表明,挤压铸造复合材料试样的抗拉强度、屈服强度和伸长率分别为296 MPa、185 MPa和12.2%,这些参数比重力铸造成型的Al-Mg-Mn合金分别提高了57%、95%和40%;比重力铸造复合材料分别提高了12%、11%和36%。分析发现,复合材料相比无添加Al-Mg-Mn合金强韧性能更高的原因在于TiB_(2)和ZrB_(2)颗粒协同增强细晶强化作用;而挤压铸造成型的复合材料的力学性能优于重力铸造成型的复合材料的主要原因在于挤压力所致的晶粒细化和Orowan强化作用。

Mechanism of Zr in in situ-synthesized particle reinforced composite coatings by laser cladding

By adding mixture of ZrOand carbon, a Zrenhanced composite coating was produced onto an AISI1045 substrate by laser cladding. The microstructure and phase formation, microhardness and wear resistance of the composite coating were studied. The experimental results indicate that the composite coating with metallurgical bonding to substrate consists of y-Ni, massive ceramic particles of ZrC,NiZr, NiZr,(Fe,Ni)Cand FeC. The in situ-synthesized ZrC particles are uniformly dispersed in composite coating, which refines the microstructure of composite coating. With different Zr02 and carbon additions, the properties are improved differently. Finally, the fine in situ ZrC particles improve the microhardness of composite coating to HV650, which is nearly 2.7 times that of Ni25 coating. Also, the composite coating has an advantage in wear resistance; it offers better wear resistance when more mixture of ZrOand carbon was added in nickel alloys.

纳米陶瓷铝合金在汽车上的应用

纳米陶瓷铝合金是采用物理或化学的方法,以铝或铝合金为基体,由一种或多种不同性质的增强物质组合而成的一种多项固体材料,该材料不仅具有基体铝合金高塑性的优点,同时具备了增强颗粒高硬度、高模量的优点。纳米陶瓷铝合金具有良好的综合性能,可广泛应用于航空航天、电子电气、汽车等领域。重点介绍了一种通过化学方法在铝合金基体中原位自生出纳米陶瓷颗粒,该方法制备出的纳米陶瓷铝合金具有轻质、高刚度、高强度、高抗疲劳、耐高温的优越性能,其力学性能远高于铝合金,同时保持了铝合金良好的加工制造性能。

CuO／Al自生复合材料的反应动力学

本文探讨了一种Ａｌ２Ｏ３粒子增强低温反应合成自生铝基复合材料的制备工艺。用热分析和电镜研究了材料的显微组织．

钛合金表面激光熔覆原位生成TiC增强复合涂层

利用Cr3 C2 和TiC生成自由能和稳定性的差异 ,通过激光熔化法在Ti6Al4V表面制备TiC颗粒增强钛基复合材料涂层。结果表明 :选择合适的激光处理工艺 ,可使Cr3 C2 和Ti合金粉末通过原位结晶置换反应生成TiC/Ti复合材料熔覆层 ;亚微米级的TiC颗粒均匀地分布于复合材料的基体中 ,复合材料的基体组织随合金粉末的成分不同而改变。

热处理对原位自生Mg_2Si/Mg-Al基复合材料组织与性能的影响

利用金属型铸造制备了原位自生Mg2Si/Mg-Al基复合材料,研究了热处理对该材料组织与性能的影响。结果表明T4处理改变了Mg2Si/Mg-Al基复合材料中Mg2Si的形貌与分布。随着保温时间的延长,棱状枝晶Mg2Si相发生熔断、球化,最终成为尺寸为10-30μm的颗粒;同时β-Mg17Al12相溶入到α-Mg基体中,在随后的时效过程中发生沉淀析出。由于β-Mg17Al12相的溶解,T4处理会降低该材料的硬度,但随后的时效析出可提高其硬度,415℃×12h固溶处理后175℃×16h(T6)时效,硬度可提高14.9%。热处理过程中棱状枝晶Mg2Si相的粒化可用吉布斯-汤姆逊定理解释。

金属基复合材料原位反应合成技术现状与展望

在现有的金属基复合材料制备技术中 ,原位反应合成技术具有显著的技术优势和经济优势 ,它已成为当今复合材料领域中最活跃的研究方向。原位反应合成技术主要有 :放热弥散法、气液反应合成法、自蔓延燃烧反应法、直接氧化法、无压力浸润法、反应喷射沉积法、接触反应法、机械合金化法等。文中综合评述了各种原位反应合成工艺方法的原理、特点和应用前景。利用原位反应合成法制备金属基复合材料 ,在同等条件下 ,其力学性能一般都高于强制法制备的复合材料。并且原位反应合成技术的原料来源广泛、价格较低 ,工艺又相对简单、制作成本低 ,适合并能够大规模工业化生产 。

铝合金表面激光熔覆原位自生TiC增强金属基复合材料涂层

以 Ti,Si C混合粉末作为预置合金涂层 ,采用 2 k W连续 Nd:YAG固体激光器进行激光熔覆处理 ,在 6 0 6 1铝合金表面借助于接触反应法制备原位自生 Ti C颗粒增强 Al- Ti复合材料涂层。试验结果表明 :采用合适的激光辐照工艺参数 ,可获得增强相 Ti C弥散分布 ,以 Ti- Al金属间化合物及 Al过饱和固溶体为主要组成相的复合材料熔覆层组织。Ti C颗粒与复合材料基体润湿良好 ,熔覆层结晶致密 ,与 6 0 6 1铝合金基材呈良好的冶金结合 。

Fe-Ti-C熔体中TiC颗粒的原位合成及长大过程研究

本文研究了Fe－Ti－C合金熔体中原位TiC颗粒的形成过程，结果表明：在合金熔体的等温过程中，Ti和C原子首先不断反应合成TiC颗粒，直至生成的TiC与熔体达到平衡；然后，TiC颗粒按照小颗粒不断溶解、大颗粒相应粗化的模式而长大其中，TiC颗粒的合成过程又可进一步分为TiC晶核的形成和长大两个阶段，形核阶段越长，熔体中TiC颗粒的数目越多．尺寸越小，而当TiC的合成反应平衡后、如继续延长等温时间，则熔体中TiC颗粒的尺寸增加。

原位合成铝基复合材料的研究现状

简介了目前反应合成铝基原位复合材料的常见复合工艺:固-液、气-液和固-固反应等。指出它们的优点是反应合成的强化相尺寸细小,与基体结合强度高,缺点是强化相种类较少,反应过程难以精确控制。其次,概述了原位铝基复合材料的常见陶瓷强化相和金属间化合物强化相良好的力学性能、耐磨性和高温性能,以及反应合成时与基体亲和力大的特点。指出反应合成的铝基复合材料的有常温力学性能高、高温性能好和耐磨性突出的优点,而存在的主要研究难题则是整个材料均质化方法不理想、生长机制等基础理论研究缺乏、反应伴生的化合物难以控制等。作者还讨论了铝基原位复合材料在民用领域的潜在应用前景。

液态反应合成Mg-Li-MgO/Mg_2Si复合材料的组织与性能

用ＤＴＡ对ＳｉＯ２ 与ＭｇＬｉ 合金反应合成复合材料的热力学进行了研究， 证明反应能够进行。检测结果表明反应生成的粒子尺寸细小且分布均匀。复合材料的强度、硬度、弹性模量明显提高； 该复合材料的延伸率低于基体合金， 但仍可达到较高水平（ ＞ ４％） ， 高于Ａｌ２Ｏ３ 及ＳｉＣ纤维增强复合材料。

碳含量对自生TiC_P增强钛基复合材料组织的影响

采用反应自生法制备了 Ti C颗粒增强钛合金基复合材料 ,并通过 XRD,SEM对复合材料的相组成和微观组织进行了研究。结果表明 :在 Ti- 6Al- 1 .8C中主要存在 Ti和 Ti C两种相。Ti C以树枝状初生 Ti C和短棒状共晶 Ti C两种形态存在。对 Ti C晶格常数的计算结果表明 ,Ti C的衍射峰存在一定的偏移 ,主要是由于 Ti C中存在 C空位。研究了 C含量对材料组织和 Ti C形貌的影响。结果表明 :C含量对基体组织基本没有影响 ,但是随着 C含量由 1 .98%减少到 0 .39% ,粗大的树枝状 Ti C逐渐消失 ,Ti C以短棒状为主 ,部分呈羽毛状。

原位TiC-AlN/Al复合材料制备及炉内气氛对反应的影响

本文首先依据化学热力学和动力学原理进行了本研究原位反应体系的母合金的研究，然后用Ａｌ－Ｔｉ－Ｍｇ合金直接Ｃ化和Ｎ化加电磁、气动双重搅拌法制备出原位ＴｉＣ－ＡｌＮ／Ａｌ复合材料。根据在真空感应炉中取出的不同反应时间的反应动力学试样的相组成和元素组成及所对应的炉内ＰＯ２的测试结果，分析了炉内气氛对反应过程和最后反应产物的影响。