Microstructure and properties of high silicon aluminum alloy with 2% Fe prepared by rheo-casting

The morphology changes of both Fe-containing intermetallic compounds and the primary Si phase of Al-20Si-2Fe-2Cu-0.4Mg-1.0Ni-0.5Mn (mass fraction, %) alloy produced by semi-solid rheo-diecasting were studied.The semi-solid slurry of high silicon aluminum alloy was prepared by direct ultrasonic vibration (DUV) which was imposed on the alloy near the liquidus temperature for about 2 min.Then, standard test samples of 6.4 mm in diameter were formed by semi-solid rheo-diecasting.The results show that the DUV treatment suppresses the formation of needle-like β-Al5(Fe,Mn)Si phase, and the Fe-containing intermetallic compounds exist in the form of fine Al4(Fe, Mn)Si2 particles.Additionally, the primary Si grows up as fine and round particles with uniform distribution in α(Al) matrix of this alloy under DUV treatment.The tensile strengths of the samples at the room temperature and 573 K are 230 MPa and 145 MPa, respectively.The coefficient of thermal expansion (CTE) between 25 °C and 300 °C is 16.052 8×10-6 °C-1, and the wear rate is 1.55%.The hardness of this alloy with 2% Fe reaches HB146.3.It is discovered that modified morphology and uniform distribution of the Fe-containing intermetallic compounds and the primary Si phase are the main reasons for reducing the CTE and increasing the wear resistance of this alloy.

Microstructure and mechanical properties of a new type of austempered boron alloyed high silicon cast steel

In the present paper, a new type of austempered boron alloyed high silicon cast steel has been developed, and its microstructures and mechanical properties at different temperatures were investigated. The experimental results indicate that the boron alloyed high silicon cast steel comprises a dendritic matrix and interdendritic eutectic borides in as-cast condition. The dendritic matrix is made up of pearlite, ferrite, and the interdendritic eutectic boride is with a chemical formula of M2B (M represents Fe, Cr, Mn or Mo) which is much like that of carbide in high chromium white cast iron. Pure ausferrite structure that consists of bainitic ferrite and retained austenite can be obtained in the matrix by austempering treatment to the cast steel. No carbides precipitate in the ausferrite structure and the morphology of borides remains almost unchanged after austempering treatments. Secondary boride particles precipitate during the course of austenitizing. The hardness and tensile strength of the austempered cast steel decrease with the increase of the austempering temperature, from 250 oC to 400 oC. The impact toughness is 4-11 J?cm-2 at room temperature and the impact

Modification Effect of P+Sr+Ce Compound on Microstructure and Properties of Cast High Silicon Heat-Resist Aluminum Alloy

The P ＋ Sr ＋ Ce compound modification technologies of as-cast Al-21Si-1.5Cu-1.5Ni- 2.5Fe- 0.5Mg alloy were investigated by means of orthogonal test. Orthogonal test results show that 3% （CaH2PO4 ＋ 2CASO4）＋ 0.2%Sr ＋ 0.2%Ce is the optimum additive of modification treatment which can fine eutectic and primary silicon also can change the form of rich-iron phase at same time. The needle form of rich-iron phase is Al9FeSi3, which is prored by X-ray diffraction analysis and X-ray energy spectrum analysis. After compound modification treatment, the needle form of rich-iron phase disappeared and the fish bone form of rich-iron and rich-Ce phase that is AlsCeFe emerged. Both at room temperature and at 300℃, the tensile strength of the alloy after the modification treatment with the optimum additive is 30% lager than that of the alloy unmodified. Observed by SEM, the brittle intercrystalline tensile fracture changed into a blended one in which has many dimples.

A High-Fe Aluminum Matrix Welding Filler Metal for Hardfacing Aluminum-Silicon Alloys

A high Fe containing aluminum matrix filler metal for hardfacing aluminum silicon alloys has been developed by using iron,nickel,and silicon as the major strengthening elements,and by measuring mechanical properties,room temperature and high temperature wear tests,and microstructural analysis.The filler metal,which contains 3.0%-5.0% Fe and 11.0%-13.0% Si,exhibits an excellent weldability.The as cast and as welded microstructures for the filler metal are of uniformly distribution and its dispersed network of hard phase is enriched with Al Si Fe Ni.The filler metal shows high mechanical properties and wear resistance at both room temperature and high temperatures.The deposited metal has a better resistance to impact wear at 220℃ than that of substrate Al Si Mg Cu piston alloy;at room temperature,the deposited metal has an equivalent resistance to slide wear with lubrication as that of a hyper eutectic aluminum silicon alloy with 27% Si and 1% Ni.

Friction Wearing Properties Research of High-silicon Aluminium Alloy Cylinder Sleeve

With tank special purpose lubricating oil,100N,200N and 800N loading force and different loading times,spray-formed high-silicon aluminium alloy and military superpower engine steel cylinder sleeve materials were used for comparative friction test and friction pair comparision test under simulated engine work condition.The results showed that,compared with steel cylinder sleeve materials,high-silicon aluminium alloy showed more excellent wearing resistance.The friction mechanism analysis of high-silicon aluminium alloy indicated that high-hardness particles in soft parent metal had determinative function,including wearing resistance and supporting ability when wearing happened.Dents on soft parent metal surface produced by friction could store oil and were helpful for lubrication.The friction trace analysis showed that,high-hardness particles in high-silicon aluminium alloy could produce friction trace on 42MnCr52 steel surface,which proved friction function of high-hardness particles in high-silicon aluminium alloy.

Nanostage Alloying of Metals in Liquid Phase

Alloying of metals is known from antiquity. Alloy making i.e., homogenizing metals started in a “hit-or-miss” way. The 1st alloy from copper (Cu) and tin (Sn) was produced around 2500 BC and from then Bronze Age began. Subsequently iron (Fe) age started after the Bronze Age. Aluminium (Al) alloying was discovered much later because pure Al could not be recovered easily even though Al is the most abundant metal in the earth’s crust. Refining of Al is a very difficult job because of its strong affinity towards oxygen. To ease alloying, melting points (mp) of the individual constituents and reactivity of metal towards oxygen were the hurdles. Now understanding the thermodynamics of metal mixing has paved alloying. Periodic properties of elements concerning size, electronegativity, crystal structure, valency, lattice spacing, etc. are considered for alloying. In this feature article, more emphasis is given to Hume-Rothery rules in which the necessary parameters for alloying have been illustrated. Importantly standard electrode potential (E0) values, eutectic, phase diagram, size-related strain in metals, etc. have been looked into in the present discussion. One elegant example is Sn-Pb alloy, known as soft solder. Soft solder was in use for many years to connect metals and in electric circuitry. Low melting, flowability, and conductivity of soft solder had placed Sn-Pb alloy a unique position in industries, laboratories and even in cottage industries. However, toxic Pb volatilizes during soldering and hence soft solder is banned almost in all countries. We felt the need for a viable alternative to obtain soldering material and then silver (Ag) based highly conducting, an eco-friendly alloy of Sn resulted in from a high boiling liquid. The discovery engenders not only a new conducting soldering alloy but also a new concept of melting metals together. Furthermore, new ideas of alloying have been generalized at their nanostages from a suitable high boiling solvent.

干式铣削Al-50wt%Si高硅铝合金刀具磨损与表面粗糙度评价

本文以Al-50wt%Si高硅铝合金为研究对象,采用单因素试验方法进行无涂层硬质合金刀具干式铣削试验,分析切削参数对刀具磨损和表面粗糙度的影响。结果表明:表面粗糙度受每齿进给量的影响最显著,随每齿进给量的增加而增加,当每齿进给量从0.07 mm/z增加到0.16 mm/z时,表面粗糙度增加2倍;刀具磨损受切削速度的影响最显著,随切削速度的增加而增加,当切削速度从140 m/min增加到260 m/min时,切削总长度降低3倍,而刀具后刀面磨损量仅是260 m/min速度下的0.8倍;表面粗糙度随刀具磨损的增加呈现先增加后降低的变化趋势,切削长度从350 mm增加到1750 mm,刀具磨损量平均增加4.5倍,而表面粗糙度却下降2倍;硬质合金刀具主要的磨损形式为磨粒磨损、崩刃。

Al-Si-Mg系铸造合金应用现状与高强韧制备研究进展

概述了Al-Si-Mg系铸造合金的应用现状与高强韧制备研究进展,系统总结了Al-Si-Mg系铸造合金晶粒细化、硅相变质、精密热处理、成分设计与成形-成性工艺装备的研究进展,归纳了各制备工艺对材料微观组织与力学性能的影响,总结了Al-Si-Mg系铸造合金高强韧制备的力学性能成果。最后,对其材料成分设计、凝固组织细晶化制备、计算机辅助工程开发与高强韧精密热处理工艺发展进行了技术展望。

低硅铝合金热裂敏感性及机理研究

为满足超高压大容量输变电设备对铸造铝合金导电性能的要求,提升高压开关导体用铸造合金的成品质量,作者研究了低硅铸造铝合金的热裂行为和力学性能。基于ProCAST对合金铸件充型、凝固和冷却过程进行模拟,对该材料铸件的热裂应力以及热裂部位进行模拟预测,同时结合约束杆法试验研究对比Si含量对合金热裂敏感性的影响规律。结果表明,所预测的热裂敏感性随合金成分变化规律与试验结果相吻合,当Si含量从0.4%提升至1.5%时,热裂敏感系数从432降低至64,同时热裂产生位置从中间杆向球端过渡,合金抗拉强度提升约8%,伸长率降低约14%。

高硅钴白合金的处理工艺研究

为解决高硅钴白合金中有价元素难以浸出的问题,在硫酸体系中,以氯酸钠作为氧化剂,并加入高硅钴白合金中的组成元素之一Fe3+作为氧化传质体,有效浸出了高硅钴白合金中的Co和Cu,并减少了Si的浸出。通过正交试验研究了初始Fe3+浓度、高硅钴白合金粒度和反应温度对浸出效率的影响,得到了优化工艺参数,并根据现实生产需求,确定了浸出成本更低的经济工艺参数。优化工艺参数为:起始Fe3+浓度为15 g/L,高硅钴白合金粒度为<0.075 mm,反应温度为85℃。其中,起始Fe3+浓度对浸出效率的影响最大。在优化工艺参数下浸出5.5 h,Co、Cu浸出率分别达到99.3%、98.7%。经济工艺参数为:起始Fe3+浓度为10 g/L,白合金粒度为0.075~0.150 mm,反应温度为85℃;浸出6.7 h后Co、Cu浸出率分别达到98.9%、98.5%。

基于遗传算法的微织构刀具织构参数仿真研究

微织构刀具切削过程中,织构参数对切削力有显著影响。为了通过优化微织构参数得到较小的切削力,利用DEFORM-3D软件建立了硬质合金刀具铣削高硅铝合金的模型,仿真得到不同微织构参数下的切削力,并结合单目标遗传算法对微织构参数进行优化求解。结果显示,优化后的微织构参数更能降低切削力。

硅固溶强化铁素体基球墨铸铁性能研究进展

介绍了硅固溶强化铁素体基球墨铸铁(或高硅球铁)的发展历程,对比分析了高硅球铁与传统球铁的拉伸性能、冲击性能、断裂韧性、疲劳强度、热导率、热循环体积变化、机械加工性能。分析表明:虽然通过控制残余镁含量、快冷等措施已经可使高硅球铁综合拉伸性能高于标准中的指标,但是常温和高温脆性的机理仍有待进一步研究;高硅球铁在疲劳强度、动态断裂韧性、热循环体积变化、机械加工性能方面要优于传统球铁。基于此,对高硅球铁发展前景进行了展望:1)高硅球铁在常温和高温脆性机理方面的研究是今后的研究重点,脆性机理研究的深入与进步将进一步提升高硅球铁的综合力学性能;2)高硅球铁与传统球铁相比有更高的的屈强比、动态断裂韧性和疲劳强度,未来会更多地应用在有轻量化需求的铸件上;3)综合考虑全生命周期成本,高硅球铁在绿色化发展趋势中更具优势。

难加工材料超高速磨削亚表面损伤研究

航空航天领域关键零部件往往采用高性能难加工材料制成,极差的可磨削性使得材料的高质高效加工成为难以突破的瓶颈。本文提出采用超高速磨削方法解决上述问题,并针对多种具有代表性的航空航天领域工程材料,包括钛合金、镍基高温合金、反应烧结碳化硅及铝基碳化硅开展超高速磨削试验,对材料表面完整性进行了表征和分析讨论。结果表明,超高速磨削可提高工件表层材料的应变梯度和温度梯度,改善难加工金属、陶瓷、复合材料的可磨削性,降低亚表面损伤深度,提高材料去除效率。本文的探索性研究为航空航天难加工材料零部件的高质高效加工提供了一条可行的技术路线,具有广阔的应用前景。

大型高硅合金电炉开炉工艺及其关键技术

针对大型高硅合金电炉开炉的工艺控制问题,结合电炉内部炉料结构及电极焙烧机理,分析了三种典型电炉开炉方式,指出了开炉过程中炉衬与电极焙烧控制、电炉负荷、投料控制之间的内在要求,对于大型高硅合金电炉开炉的生产操作具有重要的意义.

快速凝固高硅铝合金粉末形貌与组织特性研究

目的:分析高硅铝合金粉末形貌与组织特性。方法:搭配超音速气体雾化法先进行高硅铝合金粉末形貌的分析,随后,通过显微镜对粉末组织结构进行标注研究,验证结构演变和热效应,最终通过冷却速度的计算来分析过冷度的变化。结果:针对粒度25μm和45μm的高硅铝合金粉末的测定,采用四个阶段进行测试,最终得出以下结果,该粉末自身的过冷度随粒度减小而明显增大,随粒度的增大而减小,这是导致不同粒度粉末组织和结构差异的主要原因。结论:不同粒度状态下,高硅铝合金粉末与过冷度呈现反向的组织特征变动关系。

高温高真空双法兰差压变送器填充液失效分析与改进

高温高真空工况下,双法兰差压变送器在煤化工生产过程中液位测量时容易失效。失效原因为:填充液多选为高温硅油,在高温高真空工况下,很容易出现汽化现象,从而影响测量效果。填充液改为镓液态合金,具有耐高温,低膨胀率,耐负压特性,解决了填充液高温高真空下汽化问题。双法兰液位变送器远传部件采用双隔离传压结构,减少传压腔体镓液态合金的容量,解决镓基液态合金因密度和粘度大,造成仪表响应时间变长,灵敏度降低问题。改进后的双法兰差压变送器测量高温高真空液位,失效概率降低,性能得到有效提升。

高硅铝合金电子封装材料研究进展

阐述电子封装材料的基本要求,论述高硅铝合金材料的研究概况及其性能特点,分析熔炼铸造、浸渗法、快速凝固/粉末冶金和喷射沉积制备方法的优缺点,并指出高硅铝合金电子封装材料的发展方向。

高硅铝合金轻质电子封装材料研究现状及进展

综合比较了现有电子封装材料的性能及其在航空航天领域中的应用现状,较详细地阐述了高硅铝合金电子封装材料的性能特点、制备方法及研究现状,指出了高硅铝合金轻质电子封装材料的发展方向。

高硅镁合金的制备工艺及显微组织分析

The preparation technique for a high silicon magnesium alloy ASE640 was explored. Different addition forms of silicon element to magnesium melt were compared and the master alloy method was selected. In addition, microstructure and phase structure of this alloy were investigated with optical microscope, scan electronic microscope and X ray diffraction meter. The dissolution rate of Si in magnesium melt was discussed. It shows that the smaller the primary silicon strips in the master alloy are, the higher the dissolution rate and the less dissolution time are. The experimental results show that in as cast ASE640 alloy a lot of Mg 2Si intermetallic compound particles are found and they present the shape of Chinese characters. However, the mechanical properties at room temperature and creep properties at elevated temperature are decreased for the coarse Mg 2Si grains. The Mg 2Si grains can be refined by hot extrusion and dispersed uniformly in the matrix, which may efficiently improve the mechanical properties of the alloy.

电子封装用高硅铝合金热膨胀性能的研究

采用雾化喷粉与真空包套热挤压工艺制备了高硅铝合金电子封装材料，测定了合金在100-400℃间的热膨胀系数值，并运用理论模型对该温度区间的热膨胀系数进行了计算，分析了高硅铝合金材料热膨胀性能的影响因素。结果表明：Si相作为增强体能显著改善Al—Si合金的微观组织与热膨胀性能，430℃热挤压下的高硅铝合金材料在100-400℃之间的热膨胀系数平均值与Turner模型很接近。