HIP处理对TiAl基合金排气门组织和性能的影响

利用感应凝壳熔炼方法，在预热的金属型中离心浇注了名义成分为Ti-48Al-2Cr-2Nb的CA4GE型发动机用排气门。将排气门经1270℃在173MPa保温4h热等静压（HIP）处理后，其组织结构为双态组织，γ相在边界附近，尺寸较小，分布较为均匀，力学性能在815℃时σb达到470MPa，比铸态（370MPa）提高了100MPa，伸长率明显提高，达到10％以上。     

金属型离心铸造TiAl基合金耐磨性研究

利用金属型离心铸造的方法,浇注了目标成分为Ti-48Al-2Cr-2Nb的合金,随后对其进行热等静压(HIP)处理1270℃/173 MPa/4h),研究了TiAl基合金的耐磨性能。研究结果表明,在载荷为50N、加载10min和载荷为100N、加载5min时,铸态样品的摩擦因数约为0.141;TiAl基合金经热等静压处理后,在载荷为50N、加载10min和载荷为100N、加载3min时,材料的摩擦因数为0.156。通过显微组织观察发现,HIP工艺对TiAl基合金摩擦因数的影响可归结为两方面:一是消除了铸件内部的微小缩松,提高了材料的致密度;二是组织结构由全片层向双态结构的转变。     

金属型离心铸造TiAl基合金显微硬度分布规律研究

利用离心铸造的方法，浇注了目标成分为Ti-48Al—2Cr-2Nb（at．％）的合金，并对其进行热等静压（HIP）处理（1270℃／173MPa／4h），研究了样品截面内的显微硬度分布规律，以及热等静压工艺时其显微硬度分布的影响。结果表明，由于金属型离心铸造TiAl基合金内部往往存在难以消除的微观缩松，铸态样品横截面内的显微硬度分布不存在明显的规律性；HIP工艺明显减小了样品横截面的显微硬度平均值，且呈现出较强的规律性，表现为中心区域附近较高，而边缘区域较低。     

铜合金直升机旋翼配重构件的金属型铸造及工艺

采用金属型铸造并对铜合金材料进行基础试验和计算,确定了直升机旋翼配重构件的铸造工艺边界参数;利用CAD对铸造工艺参数及铸造工艺方案进行数值模拟.结果表明:经金属型铸造的铜合金密度达到理论密度的99.91%.经金属模铸造成型的铜合金直升机旋翼配重构件满足设计要求:即铸造成型后直升机配重构件的质量偏差为±5 g,曲面变形小于0.2 mm,最大截面厚度偏差为±0.1 mm.经铸造后直升机旋翼配重构件的力学性能为:σb=315 MPa,σ0.2=143 MPa,δ=25%,HB=950.     

自耗电极/感应凝壳熔铸TiAl基合金成分均匀性研究

利用重力和离心铸造方法，在金属型中浇注了目标成分为Ti-48Al-2Cr-2Nb（原子分数，％）的TiAl基合金，随后对其进行热等静压（HIP）处理（1270℃／173MPa／4h），研究了合金中各元素的分布均匀性。结果表明，熔炼过程中Al元素将产生一定的挥发。使得重力和离心浇注的TiAl基合金中Al元素含贯均低于目标成分，离心力场对成分均匀性无明显影响。各种元素沿铸件横截面径向分布基本上是均匀的，微观区域内的成分波动可通过HIP工艺得到显著的改善。     

壁厚对ZA52镁合金半固态挤压件组织性能的影响

采用优化的试验参数,在四柱压力机上对ZA52镁合金进行半固态触变挤压试验,制备出阶梯试样.对其不同壁厚处的组织、性能进行了分析,并与金属型浇注、半固态压铸做了对比.结果表明:挤压件中出现液固分离现象；随着壁厚的减小,其固相颗粒组织由近似圆形过渡为梭形,有些颗粒甚至压合在一起；其抗拉强度由208.4MPa增加到270.1MPa、伸长率由7.10％增加到17.71％,最小壁厚处综合力学性能最好,且明显优于金属型浇铸及半固态压铸.     

挤压铸造AZ91D和AM50A的组织与力学性能研究

研究了挤压铸造AZ91D、AM50A镁合金的组织与力学性能及稀土元素和热处理对合金组织与力学性能的影响.试验结果表明,挤压铸造使α相枝晶细化,形态改善,β相细小呈不连续分布;减少了缩松、气孔等缺陷,从而提高了镁合金铸件质量和力学性能.铸态AZ91D的力学性能为σb=238 MPa、δ5=5.5%、HBS75、Ak=7.8 J;AM50A为σb=224 MPa、δ5=9.4%、HBS56、Ak=12.1 J.稀土元素使镁合金组织细化,析出富铝稀土相,提高了镁合金的抗拉强度和硬度,但伸长率和冲击韧度降低.挤压铸造镁合金件经固溶处理后,β相大部分溶解并固溶于α相中,提高了镁合金的强塑性;再经时效处理,析出细小弥散的二次β相,进一步使镁合金强化.在合适的挤压铸造工艺参数和热处理下,铸件的力学性能可达AZ91D为σb=263 MPa、δ5=7.4%、HBS90、Ak=12 J;AM50A为σb=251 MPa、δ5=11.8%、HBS74、A k=16.5 J.     

湿型砂冷模法金属型离心铸管的生产技术

湿型砂冷模法金属型离心铸管技术，是金属型在冷态下衬以湿型砂，在卧式离心铸造机上浇铸，以获得高延性管材的新技术。该技术不但可生产球墨铸铁上水管、燃气管，而且可以生产一般金属型离心铸造难以生产的双法兰、双承口等特种管型的管材。介绍了该技术的主要工艺和设备。     

金属型铸造ZA50合金的力学性能和组织

研究了金属型铸造Zn-50Al（ZA50）高强度铸造耐磨合金的组织和力学性能。结果表明，ZA50合金金属型铸态组织为α相和（α＋η）共析组织及合金化合物，抗拉强度（σb）可达477MPa，金属型铸造＋200℃时效处理的组织为α相和粒状（α＋η）共析组织及合金化合物，抗拉强度（σb）可达354MPa，ZA50合金比ZA27合金有更高的强度和断裂韧度。分析了合金元素形成的化合物在ZA50合金中的形貌特征。     

固液铸造技术在高锰铝合金中的应用研究

通过加入同种成分粉末,研究了Al-Mn合金的固液混合铸造工艺,初步探索固液混合铸造后的金相组织及力学性能变化.采用该技术获得的Al-Mn合金坯料的金相显微组织均匀,晶粒细小,呈等轴状或近等轴状.采用固液混合铸造的室温力学性能σb=130MPa, σ0.2=80MPa, δ=1.2%;优于传统铸造和半固态铸造合金,使难以应用的高锰铝合金有了应用可能.     

金属型离心铸造气门座

叙述金属型离心铸造内燃机气门座的工艺方法和材料特点。经生产实践证明：选用高碳当量(CE)、高硅、锰及铬铜合金铸铁，用金属型离心铸造生产的内燃机气门座成本低、质量好。     

浇注时功率(ISM)对TiAl基合金铸件表面质量的影响

采用感应凝壳熔炼（ＩＳＭ）法熔炼了Ｔｉ－４８％Ａｌ－２％Ｃｒ－２％Ｎｂ合金,以静态浇注和离心浇注两种条件在金属型中浇注了汽车排气阀。通过分析阀体的成形情况,总结了浇注时功率对合金填充能力和铸件表面质量的影响规律。结果表明,ＩＳＭ法熔铸ＴｉＡｌ基合金时,合金的线收缩量随浇注时功率的提高而增大,离心浇注可有效地抑制收缩,浇注时功率处于２００至２８０ｋＷ范围内所得铸件表面质量较为理想。     

TiAl基合金排气阀立式离心铸造充型及凝固过程数值模拟

以N-S方程、连续性方程及Fourier导热方程为基础，结合离心力、重力及Coriolis力，在实验的基础上建立了立式离心铸造充型过程及凝固过程数学模型．并且依据此模型对TiAl基合金排气阀立式离心铸造过程温度场、流场及压力场进行了数值模拟．数值模拟结果表明，离心铸造的充型过程存在正向和反向两个充填过程，在入口处易出现卷气缺陷．凝固过程也存在正向和反向两个凝固顺序，在靠近先充填一侧易于形成偏轴线缩松缺陷．     

Precision casting of Ti-15V-3Cr-3AI-3Sn alloy setting

In this research, Ti-15V-3Cr-3Al-3Sn alloy ingots were prepared using ceramic mold and centrifugal casting. The Ti-15V-3Cr-3Al-3Sn setting casting, for aeronautic engine, with 1.5 mm in thickness was manufactured.The alloy melting process, precision casting process, and problems in casting application were discussed. Effects of Hot Isostatic Pressing and heat treatment on the mechanical properties and microstructure of the Ti-15V-3Cr-3Al-3Sn alloy were studied.     

Precision casting of Ti-15V-3Cr-3Al-3Sn alloy setting

In this research, Ti-15V-3Cr-3Al-3Sn alloy ingots were prepared using ceramic mold and centrifugal casting. The Ti-15V-3Cr-3Al-3Sn setting casting, for aeronautic engine, with 1.5 mm in thickness was manufactured. The alloy melting process, precision casting process, and problems in casting application were discussed. Effects of Hot Isostatic Pressing and heat treatment on the mechanical properties and microstructure of the Ti-15V-3Cr-3Al- 3Sn alloy were studied.     

Numerical simulation for permanent mold centrifugal cast TiAl exhaust valve

1INTRODUCTION Inthepastdecades,therehasbeenanenor mousincreaseintheresearchontitaniumalumin ides,inparticular,ontheTiAlcompounds[13].Thelowdensitycombinedwiththehigh strengthathightemperaturemaketitaniumaluminidealloy anexcellentcandidateforautomotiveexhaustvalve applications[47].ThekeytosuccessfulapplicationofTiAlexhaustvalvesisneitherthestrengthnor theductility,butalargeoutputandlowcostman ufacturingmethod[810].Numericalsimulationforthefillingandsolidi ficationofcastingshasbeenresearch…     

Aluminum alloy pistons reinforced with SiC fabricated by centrifugal casting

Hypereutectic Al-Si alloy-based composite pistons reinforced with SiC particles locally at the head were fabricated by centrifugal casting. The effects of various technique parameters, i.e., the slurry temperature of the alloy, the mold temperature and the rotation speed of the mold, on the particle segregation were investigated, and the macromorphologies and microstructures of pistons were observed. The mechanical properties, such as hardness and wear resistance along the axis of the piston and the thermal expansion coefficient at the piston head, were measured. The results showed that, (1) centrifugal casting can be used as a new and effective method in manufacturing pistons, and reasonable parameters were 850 °C, 600 °C and 800 rpm for the slurry temperature of the alloy, the mold temperature and the rotation speed of the mold, respectively; (2) the hardness values of pistons fabricated by centrifugal casting gradually increased from the piston skirt to the piston head, and the average hardness value in piston heads was improved by 23.7HRB over that of pistons fabricated by gravity permanent mold casting; (3) the piston heads showed excellent wear resistance, and the wear rate of piston heads decreased by 70.3% over that of the piston fabricated by gravity permanent mold casting; and (4) the average linear expansion coefficient of the piston head was 15.3 × 10⁻⁶ K⁻¹ and decreased by 23.1% over that of pistons fabricated by gravity permanent mold casting.     

Microstructure evolution and mechanical properties of Mg-12Zn-2Y alloy containing quasicrystal phase fabricated by different casting processes

Although icosahedral quasicrystal phase (denoted as I-phase) has been verified as an outstanding reinforcing phase, the mechanical properties of quasicrystal-reinforced Mg-Zn-Y alloys fabricated by traditional casting processes are still unsatisfactory due to the serious segregation of intermetallic compounds. In this study, the microstructure and mechanical properties of Mg-12Zn-2Y alloy fabricated by different casting processes, including permanent mold casting, squeeze casting and rheo-squeeze casting with ultrasonic vibration, were systematically investigated and compared. The results show that massive, large-sized I-phase and Mg₇Zn₃ phase gather together in the permanent mold cast sample, while the squeeze casting process leads to the transformation of I-phase into fine lamellar morphology and the amount of Mg₇Zn₃ decreases. As to the rheo-squeeze casting process, when the ultrasonic vibration is exerted with power from 800 W to 1,600 W, the α-Mg grains are refined and spheroidized to a large extent, and the lamellar spacing of the eutectic structure is significantly reduced, accompanied by some tiny granular I-phase scattering in the α-Mg matrix. However, when the ultrasonic power continuously increases to 2,400 W, the eutectic structure becomes coarse. The best mechanical properties of the rheo-squeeze cast alloy are obtained when the ultrasonic power is 1,600 W. The microhardness, yield strength, ultimate tensile strength and elongation are 79.9 HV, 140 MPa, 236 MPa, and 3.25%, which are 44.1%, 26.1%, 25.5%, 132.1% respectively higher than the corresponding values of the squeeze casting sample, and are 47.6%, 44.3%, 69.8%, and 253.3% respectively higher than the corresponding values of the permanent mold casting sample.

     

退火处理对金属型铸态奥-贝球铁组织和性能的影响

对金属型铸态生产的奥-贝球铁进行退火处理以改善力学性能,通过正交试验研究退火工艺对其组织和性能的影响.试验结果表明:退火处理对石墨形态无明显影响,但会改变基体中贝氏体的类型;低温退火可在硬度变化不大的情况下有效地提高金属型铸态奥-贝球铁的强度和塑性、韧性,抗拉强度可达到1080MPa.这表明了金属型铸造和退火处理相结合的方法可获得高性能铸态奥-贝球铁.     

Effect of mold temperature and casting dimension on microstructure and tensile properties of counter-gravity casting Ti-6Al-4V alloys

The cast Ti-6Al-4V alloy bars with different section sizes were fabricated by investment casting at counter-gravity condition with the mold temperatures of 300 °C and 650 °C, respectively. The microstructure of the alloy was observed by means of OM and SEM, and the effect of mold temperature and casting dimension on tensile properties was studied. Results show that equiaxed grains are obtained regardless of the casting dimension. β grain size tends to increase with an increase in mold temperature. Hot isostatic pressing of the alloy was carried out for tensile properties' comparison. Room temperature tensile test results show that Ti-6Al-4V alloy produced via counter-gravity casting has good balance of strength and ductility after hot isostatic pressing(HIP). The alloy shows higher ductility due to the elimination of porosity. In both cast and HIP status, the tensile strength is inclined to decrease with an increase in mold temperature, while the ductility is prone to slightly increase. Both the strength and ductility tend to decrease with an increase in the casting dimension.