复杂空心涡轮工作叶片表面细晶工艺研究

针对由K465合金制造的复杂、空心涡轮工作叶片表面细晶的不同要求,研究了制备叶片陶瓷型壳时,采用在精铸型壳内表面均匀涂挂一层350号铝酸钴作为表面细晶孕育剂,其加入量分别为0、35%、45%～65%及100%时对叶片表面低倍晶粒度的影响;同时研究了细晶孕育剂加入量一定时,浇注叶片时冷却环境对叶片表面低倍晶粒度的影响。研究结果表明,未经孕育处理的试片表面晶粒粗大,而经铝酸钴细晶孕育剂处理后试片表面晶粒细小。当铝酸钴加入量为45%～65%时,叶片采用热型浇注,型壳细砂做填砂,能够使复杂、空心涡轮工作叶片表面低倍晶粒度的合格率达到90%以上。另外,工艺可行性验证结果也表明,中、外叶片显微组织、力学性能相当。

细晶铸造工艺研究

用热学方法通过实验来研究细晶铸造工艺过程,其中浇注温度和过热温度等关键工艺参数都是经过实验比较确定的,这对实际生产有一定参考作用。实验所得到的细小晶粒结构的试样,其具有优良的低周疲劳性能,并且破断性能没有受到损失。

细晶工艺制备高性能烧结钕铁硼的研究

研究了烧结钕铁硼制备中磁粉粒度与烧结温度以及磁性能之间的关系。研究结果表明:随着磁粉粒度的降低,磁体的矫顽力Hcj增加;但磁粉粒度降低至2.4μm以下时,Hcj不再继续增加,反而降低。另外,对比研究了采用细晶工艺制备的Co含量不同的钕铁硼磁体的耐蚀性能,结果表明Co可以显著改善磁体的失重。

Strength and plasticity improvement induced by strong grain refinement after Zr alloying in selective laser-melted AlSiMg1.4 alloy

In order to enhance the mechanical properties of the selective laser-melted(SLM) high-Mg content AlSiMg1.4 alloy,the Zr element was introduced.The influence of Zr alloying on the processability,microstructure,and mechanical properties of the alloy was systematically investigated through performing microstructure analysis and tensile testing.It was demonstrated that the SLM-fabricated AlSiMg1.4-Zr alloy exhibited high process stability with a relative density of over 99.5% at various process parameters.Besides,the strong grain refinement induced by the primary Al3Zr particle during the melt solidification process simultaneously enhanced both the strength and plasticity of the alloy.The values for the yield strength,ultimate tensile strength,and elongation of the SLM-fabricated AlSiMg1.4-Zr were(343±3) MPa,(485±4) MPa,and(10.2±0.2)%,respectively,demonstrating good strengthplasticity synergy in comparison to the AlSiMg1.4 and other Al-Si-based alloys fabricated by SLM.

K417G涡轮整体叶盘叶片裂纹原因分析与验证

针对K417G合金铸造涡轮整体叶盘在发动机试车考核中出现的叶片裂纹问题,基于裂纹叶片断口宏观、微观分析及低倍组织检查结果,开展了粗晶铸造和表面细晶铸造试样的力学性能对比测试及叶片共振转速分析。结果表明,整体叶盘叶片裂纹产生的主要原因是高压涡轮导叶数24激起的3阶共振,同时粗晶铸造和叶片根部厚度偏薄也降低了叶片的疲劳抗力。为此,采取改变高压涡轮导叶数、增加叶片根部厚度和改用表面细晶铸造工艺等措施,有效避开了叶片危险共振并提高了叶片的疲劳抗力。经后续试验验证考核,叶片采取上述措施后不再出现裂纹问题。

通过控制δ相以优化IN718合金锻件的组织和性能

在试验研究工作的基础上,提出了通过控制δ相获得细晶组织的IN718合金锻件的锤上锻造工艺(以下简称细晶锻造工艺)。通过光学金相检验,室温和65 0℃拉伸试验,65 0℃光滑和缺口持久试验研究了细晶锻造工艺对IN718合金锻件的组组和性能的影响。试验结果表明,所提出的工艺可获得晶粒尺寸11μm (ASTM 10级)以下,且晶粒组织均匀的IN718合金锻件。锻件的力学性能指标能达到,甚至超过DA锻造工艺生产的IN718合金锻件的水平。上述结果是由于,所提出的锻造工艺要求在终锻工序之前,坯料在90 0℃保温4h ,即进行所谓中间热处理,以使δ相适当析出,形成魏氏体组织。这种组织,一方面,保证终锻后锻件的晶粒细小而均匀,从而达到要求的强度指标;另一方面,使δ相在终锻后直接时效过程中在晶界上呈不连续的颗粒或短棒状分布,从而使锻件的持久性能满足技术条件的要求。

Grain refinement in AZ31 magnesium alloy rod fabricated by extrusion-shearing severe plastic deformation process

A new severe plastic deformation （SPD） method that is extrusion-shearing （ES）, which includes initial forward extrusion and shearing process subsequently, was developed to fabricate the fine grained AZ31 Mg alloys. The components of ES die were manufactured and installed to gleeble1500D thermo-mechanical simulator. Microstructure observations were carried out in different positions of ES formed rods. The results show that homogeneous microstructures with mean grain size of 2 μm are obtained at lower temperature as the accumulated true strain is 2.44. Occurring of continuous dynamic recrystallization （DRX） is the main reason for grain refinement during ES process. The experimental results show that the ES process effectively refines the grains of AZ31 magnesium. The production results of ES extrusion with industrial extruder under different extrusion conditions show that the ES extrusion can be applied in large-scale industry.

Melting purification process and refining effect of 5083 Al-Mg alloy

To improve the poor stability of casting process of Al alloy with high Mg content, which leads to poor final product quality, the melting purification process and the influences of the refiner on the microstructure and defect of 5083 alloy were studied. The results show that the optimized process for the rotary impeller degassing of 5083 alloy is as follows： a rotary speed of 250-400 r/min; a gas flow of 1.2-2.0 L/s, a refining time of 10-15 min. This optimized process can reduce the gas content in the solid alloy to 2× 10^-3 mL/g or lower. Due to the addition of grain refiner, the cast microstructure of 5083 alloy is refined. The Al-5Ti-IB wire shows the best refining effect among all the refiners. The refining effect is improved with the increase of grain refiner addition amount. And the refinement effects become stable when Ti content reaches 0.1% or higher. The surface crinkling defect of the billet can be easily found in the alloy refined with Al-5Ti-IB wire compared with the alloys refined with other refiners.

Microstructure and phase forming process of Al-3Ti-0.2C-1RE grain refiner

An Al-3Ti-0.2C-1RE grain refiner was prepared by in-situ reaction method.The microstructure was investigated by optical microscopy(OM),scanning electron microscopy(SEM) equipped with energy-dispersive spectrometry(EDS) and X-ray diffraction(XRD).The results show that the Al-3Ti-0.2C-1RE grain refiner is composed of α-Al,TiAl3,TiC and Ti2 Al20 Ce phases.Compared with Al-3Ti-0.2C refiner,the morphology of TiAl3 phase is changed and Ti2 Al20 Ce phases form with the addition of RE.Accordingly,the refining performance is improved.The phase forming process of the refiner is as follows: Blocky Ti2 Al20 Ce and fine blocky TiAl3 form in the melt at the initial stage of reaction,then the fine blocky TiAl3 gradually disappears,and the blocky Ti2 Al20 Ce grows bigger with the increase of holding time.The predominant mechanism to synthesize TiC particles is the reaction between high concentration of solute Ti atoms and graphite particles.