Fe—Mn—Si系统结钢显微组织的观察与分析

观察了含硅凶母合金烧结钢的组织变化和合金元素锰，硅的分布情况。发现：添加硅锰母合金后，在１１００℃以上为液相烧结，但只有小尺寸母合金颗粒熔化后留下的孔洞趋于球形，较大尺寸母合金颗粒则在其周围留下环形孔洞。     

硅锰母合金在对烧结钢性能和组织的影响

通过添加硅锰母合金，将硅，锰这两种对氧亲和力较高的元素加入到烧结钢中，以改善烧结钢的力学性能，结果表明，当硅含量为１．１％～１．７％，锰含量为２．７％，碳含量为０．３５％时，烧结钢的强度可以超过８００ＭＰａ，但添加硅锰母合金对冲击韧性有不利影响，两种不同成分的母合金相比较，但添加硅锰母合金对冲击韧性有不利影响，两种不同成分的母含金相比较，硅锰含量主的母合金的烧结钢的力学性能影响较显著。     

硅锰母合金对烧结钢性能和组织的影响

通过添加硅锰母合金,将硅、锰这两种对氧亲和力较高的元素加入到烧结钢中,以改善烧结钢的力学性能。结果表明,当硅含量为1.1%~1.7%,锰含量为2.7%,碳含量为0.35%时,烧结钢的强度可以超过800MPa。但添加硅锰母合金对冲击韧性有不利影响。两种不同成分的母合金相比较,硅、锰含量高的母合金对烧结钢的力学性能影响较显著。     

MCM母合金对铁基材料性能的影响

本文研究了MCM母合金(即含有锰、铬、钼的铁合金粉)对粉末冶金铁基材料性能的影响及MCM母合金中诸合金元素在组织中的分布状态。发现,加入MCM母合金粉末可促进烧结致密化过程,显著提高材料的抗拉强度和硬度,抗拉强度可为同碳量材料的2.5倍左右;通过对材料组织的电子探针分析并比较Fe-Mo混合二元系烧结过程中钼的扩散情况,表明,以MCM母合金形式加入合金元素钼与Fe-Mo混合二元系相比,钼的均匀化程度可提高一倍,但MCM母合金中诸合金元素在组织中的分布并不相同,钼的扩散情况较好,铬次之,而锰的扩散量极微。     

高碳高钒模具钢CPM10V的真空烧结组织

观察了脱氧还原的水雾化ＣＰＭ１０Ｖ预合金粉末压坯在真空中不同温度烧结后的金相组织。结果表明：在１２５０℃以上烧结时，烧结体中原粉末颗粒边界消失；在１２７０℃以下烧结，碳化物细小、尺寸均匀，但残留孔隙较多且尺寸较大；在１２８０℃以上烧结，碳化物迅速长大并且出现了尺寸相差较大的两类碳化形物，残留孔隙较少且尺寸较小，上述两种不同的孔隙、碳化物形貌是由固相烧结和液相烧结两种不同烧结机制引起的。     

细晶钨合金内部组织均匀性研究

喷雾干燥法制备超细粉末,使用低温烧结技术制备钨合金制品,分别对超细钨合金和常规钨合金进行力学性能测试,并采用超声波探伤技术检测超细钨合金和常规钨合金的内部组织,探伤结果显示超细晶钨合金内部没有发现缺陷,而常规钨合金内部有两处鸟巢状缺陷,分别对缺陷部位和没有缺陷部位进行金相分析,金相显示缺陷部位是液相缺失导致的钨颗粒聚集,聚集的钨颗粒没有液相填充出现很多孔洞。     

含铜铁基粉末冶金零件烧结性能的研究进展

含铜铁基粉末冶金材料在烧结前后易发生尺寸变化,为此类零件的生产带来不便。本文介绍了有关含铜铁基粉末冶金材料的烧结过程、烧结过程中铁铜粉末颗粒尺寸变化和烧结尺寸变化的相关研究进展,主要包括以下内容:高于Cu熔点温度烧结时,Cu颗粒熔化扩散渗入Fe颗粒中,在Cu颗粒原本位置形成流出孔隙,从而造成烧结坯尺寸的膨胀;随着烧结温度或烧结时间的增加,烧结过程中铁铜粉末颗粒的尺寸呈增大趋势;影响含铜铁基粉末冶金材料烧结尺寸变化率的主要因素是粉末粒度及合金元素的成分和含量。     

细粒级铁矿粉对烧结液相和矿结构的影响

利用基础烧结设备检测了细粒级铁矿粉同化速度、流动能力,并通过微型烧结杯模拟料层下部单元点烧结过程的方法来研究配加15%细粒级矿粉的烧结矿结构变化,有效分析了3种细粒级矿粉在烧结时的液相行为及对烧结矿结构和性能的影响。通过比较生产用混匀矿与配加质量分数为15%的A、B、C粉的烧结矿结构表明:A粉有利于减少烧结矿内部孔洞的尺寸,减少核颗粒和液相间较大孔洞的数量,并能促进针铁矿发展;B粉会增加烧结矿内部大孔洞,增加柱状或片状铁酸钙的生成;C粉同化速度慢,液相流动能力差,粘结效果差,会使液相与核颗粒间孔洞尺寸和数量增加。烧结杯试验结果表明:在生产用混匀矿中使用质量分数为15%的A粉,烧结矿的转鼓指数提高2.94%,低温还原粉化指数(RDI)降低3.37%。     

含锰高强度低合金烧结钢(Ⅰ)——成分系列

锰是钢铁工业中重要的合金化元素.该文作者评述了含锰高强度低合金烧结钢的成分系列及性能,指出:锰作为烧结钢的重要合金元素,具有突出的强化效果,可以取代铜、镍、铬和钼等价格较贵的金属元素;含锰低合金烧结钢强度高,烧结尺寸变化可控,适用于制造承受中、高载荷的机械零件.     

粗大钴团在硬质合金烧结过程中的演变

钴池是降低硬质合金抗弯强度的一种缺陷,常以内表面存在一层钴膜的孔洞形式存在,压坯中的粗钴团是形成合金中钴池的主要因素。本文在90%WC+10%Co(质量分数)混合粉末中掺入粗大钴团(100~400μm),压制成形后分别在950、1 290、1 310、1 330、1 350和1 410℃烧结,保温时间为5 min。用SEM和金相显微镜研究粗钴团在各温度段的形貌,结果表明:在较低温度(≤1 310℃)烧结后,合金中钴团发生固相烧结,以蜂窝结构存在于孔洞中;继续升高温度,钴部分转变为液相并少量渗入合金组织中,冷却后留下孔,且孔表面有岛状的钴;当烧结温度≥1 410℃时,过量液相铺展在孔内表面,冷却后在合金孔内表面形成一层钴膜。     

CSP薄板坯连铸包晶反应区域的研究

研究了冷却速率和硅、锰合金元素含量对Fe-C合金的包晶反应和包晶点位置的影响;由于CSP薄板坯冷却速率快,Fe-C相图向左下方移动,包晶反应区域的碳含量为0.08%～0.20%;在钢中其它成分不变的条件下,硅含量增加,锰含量减少,包晶点处的碳含量会提高.     

高硅镁合金的制备工艺及显微组织分析

汽车发动机传动系统可采用的镁合金有AZ91D ,AM 6 0B合金[1,2 ] 。但是这些合金的抗蠕变能力较低 ,使镁合金构件与与之连接的构件间易产生旷动 ,最终导致失效。目前所开展的耐热镁合金的研究 ,其目标是在不大幅度提高成本的基础上 ,提高镁合金在 15 0～ 2 5 0℃下的高温强度和蠕变性能 ,并且具有良好的压铸性能和耐蚀性[3～ 5] 。本实验研究了高硅镁合金的熔炼制备工艺 ,分析了合金的显微组织结构。1　试验过程镁合金熔炼前首先按照实验计划进行合金的配料计算 ,然后准备炉料及所需的非金属辅助材料。将坩埚预热至暗红色 (4 0 0～ 4 5 0…     

Dissolution of iron intermetallics in Al-Si Alloys through nonequilibrium heat treatment

Conventional heat treatment techniques in Al-Si alloys to achieve optimum mechanical properties are limited to precipitation strengthening processes due to the presence of second-phase particles and spheroidization of silicon particles. The iron intermetallic compounds present in the microstructure of these alloys are reported to be stable, and they do not dissolve during conventional (equilibrium) heat treatments. The dissolution behavior of iron intermetallics on nonequilibrium heat treatment has been investigated by means of microstructure and mechanical property studies. The dissolution of iron intermetallics improves with increasing solution temperature. The addition of manganese to the alloy hinders the dissolution of iron intermetallics. Nonequilibrium heat treatment increases the strength properties of high iron alloys until a critical solution temperature is exceeded. Above this temperature, a large amount of liquid phase is formed as a result of interdendritic and grain boundary melting. The optimum solution treatment temperature for Al-6Si-3.5Cu-0.3Mg-lFe alloys is found to be between 515 °C and 520 °C.     

Microstructure of high-tensile strength brasses containing silicon and manganese

The morphology, crystallography, chemistry, and distribution of the phases in commercial high-tensile strength brasses containing manganese and silicon with compositions conforming to U.S.A. Specifications C67300 (Cu-35Zn-2.5Mn-lSi) and C67400 (Cu-35Zn-2.5Mn-lSi-l.5Al) have been studied. The wrought and cast microstructures of both types of alloys consist of the copper-rich feea phase, ordered B2β’ phase, and a manganese silicide Mn₅Si₃, with the crystal structure D8₈. Particles of Mn₅Si₃ are distributed uniformly in the as-cast alloy C67300 but tend to concentrate at theβ′ boundaries in alloy C67400. Studies of the development of the microstructure show that Mn₅Si₃ particles form from the liquid and are also precipitated from solid solution. During cooling, the α phase precipitates at a higher temperature in alloy C67300 (800 °C) than in alloy C67400 (500 °C); nucleation of the α phase occurs on Mn₅Si₃ particles in alloy C67400. Tiny Mn₅Si₃ precipitates are formed in both alloys upon quenching from temperatures near the solidus. When the quenched specimens are tempered at temperatures between 400 °C and 500 CC, all of theβ′ phase transforms to α in alloy C67300, while in alloy C67400, α precipitation occurs at theβ′ boundaries and shows a Widmanstätten morphology.     

Microstructural change during liquid phase sintering of W−Ni−Fe alloy

The changes of bulk density and microstructures during heating and liquid phase sintering of 98W-1Ni-1Fe compacts prepared from 1 and 5 μm W powders have been observed in order to characterize the densification behavior. The compact prepared from a fine (1 μm) W powder begins to densify rapidly at about 1200°C in the solid state during heating, attaining about 95 pct density upon reaching the liquid phase sintering temperature of 1460°C. The compact prepared from a coarse (5 μm) W powder begins to densify rapidly at about 1400°C in the solid state, attaining about 87 pct density upon reaching the liquid phase sintering temperature. Thus, the skeleton of grains is already formed prior to liquid formation. During the isothermal liquid phase sintering, substantial grain growth occurs, and the liquid flows into both open and closed pores, filling them sequentially from the regions with small cross-sections. The grains subsequently grow, into, the liquid pockets which have been formed at the pore sites. The sequential pore filling by first liquid thus is shown to be the dominant densification process during the liquid phase sintering of this alloy, as has been demonstrated earlier with spherical model pores and as predicted theoretically.     

The atomic-structure changes in Al-16 pct Si alloy above the liquidus

The atomic-structure changes in an Al-16 pct Si alloy above the liquidus have been studied by a θ-θ high-temperature X-ray diffractometer, rapid solidification, a vertical centrifugal casting apparatus, and differential scanning calorimetry (DSC) measurements. It was found that the diffraction intensity and structure-factor (S(Q)) curves for an Al-16 pct Si alloy have small prepeaks at small Q values when the temperature is high enough. Rapid-solidification and centrifugal-casting experimental results show that the primary silicon phase can easily coarsen and segregate under additive force after an overheat at high temperatures. The DSC measurements show that the temperature and latent heat of primary solidification rise with the temperature of overheating. These experimental results suggest that a strong interaction occurs between Si-Si atoms in a liquid Al-16 pct Si alloy at high temperatures, resulting in the microsegregation of Si atoms in the melt.     

Effect of Y Addition on Microstructure and Constituent Phases of Al-Ti-C Master Alloy

Al-Ti-C master alloy was prepared by SHS (Self-propagating High temperature Synthesis)-melting technique. Effect of yttrium addition level on the microstructures of the master alloy was studied by XRD, SEM and EDS. The experimental results show that the addition of 1.0%Y is beneficial to the formation of TiC particles; Al-Ti-C-1.0Y consists of rod-like and blocky TiAl3, TiC, Al3Y and α-Al matrix. Y is found around TiC particles in Al-Ti-C-0.5Y master alloy while blocky (AlTiY) phase appears in Al-Ti-C-1.0Y master alloy. Al3Y with dendritic morphology and small blocky Al2Y except for TiC are found in Al-Ti-C-2-0Y master alloy.     

Phase transformations in a binary 10 at % Si-90 at % Al alloy at high pressures and temperatures

Differential barothermal analysis of the phase transformations in a 10 at % Si-90 at % Al alloy has been performed at temperatures up to 700°C in an argon atmosphere compressed to 100 MPa. A slight change of the eutectic melting/solidification temperature is found. The liquidus temperature of the alloy, which is determined upon melting and solidification, coincides with that determined at atmospheric pressure. At 551–554°C, an aluminum-based solid solution decomposes with the formation of silicon nanoprecipitates. The porosity of the alloy after barothermal analysis is almost unchanged. The lattice parameters of micron-sized silicon particles decrease, whereas those of nanoparticles increase relative to the tabulated parameters. The lattice parameters of aluminum subjected to solidification and cooling in a compressed argon medium decreases. The micorhardness of the aluminum matrix of the alloy corresponds to that of pure aluminum.     

Some data on the infiltration of porous iron-manganese alloys with copper and its alloys

Summary It is clearly shown that nonporous iron-manganese-copper alloys can be produced by infiltrating an iron-manganese matrix with copper or copper alloys.Additional data have been obtained on the effectiveness of copper, a copper-manganese master alloy, and brass as infiltrating materials; the feasibility of producing a nonporous iron-manganese alloy free from oxide inclusions is demonstrated.Data are presented on the formation of iron-manganese-copper alloys with different manganese contents during infiltration with copper and copper-manganese master alloys, under different infiltration conditions.The extent of phase interaction during infiltration and the condition of boundaries in alloys produced under different infiltration conditions have been investigated.     

Nucleation on ceramic particles in cast metal-matrix composites

In order to understand the nucleation on ceramic particles in the melts of metal-matrix composites (MMCs), the effect of segregation of solute on the surface of reinforcement particles in the melt has been analyzed as a function of particle temperature and the surface energy of the particle/liquid melt. The temperature of the particle in the melt, calculated analytically, was found to become close to the melt temperature within a very short time of contact between the particle and the melt. The solute concentration near the particle surface will, therefore, primarily be influenced by the surface energy of the particle and the melt. Based on this, the undercooling due to solute segregation around the particle and the chemical free-energy change due to the formation of the new solid phase on the particle were calculated in selected hypo- and hypereutectic Al-Si alloy melts containing (1) SiC particles or (2) graphite particles. The chemical free-energy change (driving force for nucleation) due to the formation of the new phase on the particle is lower for hypoeutectic compositions than for hypereutectic compositions in the aluminum-silicon alloy systems; this is due to the higher undercooling in the hypereutectic alloys due to solute segregation on the surface of the particle. This suggests that the formation of the primary phase on the surfaces of particles in the melt should be more favorable in the hypereutectic compositions than for hypoeutectic compositions. This also indicates that even when the particle temperature is not significantly lower than the liquidus temperature, nucleation on the particles can take place due to the segregation of the solute on the particles. Experimental observations of the microstructure of several cast metal-matrix composites, including Al-Si-SiC and Al-Si-graphite, show (1) the presence of silicon in contact with the reinforcement particles in hypereutectic alloys, suggesting that nucleation and growth of primary silicon under certain conditions occurs on silicon carbide and graphite particles, possibly due to solute segregation on the surface of the particles, and (2) the presence of reinforcement particles in the last-freezing interdendritic regions of the primary phases in hypoeutectic alloys, suggesting the absence of nucleation of primary phases on the reinforcement surface, as predicted by the analysis.