铈对铝合金定向凝固过程溶质再分布的影响

本文采用高温度梯度的定向凝固装置(LMC法),在可控的工艺条件下获得了Al—Cu—Ce合金的固液界面形态。在合金中加入微量的铈使平面界面前沿出现失稳,界面上出现了聚集溶质的凹坑及沟槽。且随着铈含量的增加,这些凹坑及沟槽逐渐变深。根据晶体生长的界面稳定性动力学理论,认为铈使得合金界面不稳定是铜的实际分配系数减少和熔化潜热增加的综合作用的结果。     

Effect of Yttrium Addition on Microstructures and Room Temperature Tensile Properties of Ti-47Al Alloy

The microstructures and room temperature tensile properties of a series of Ti-47Al-xY （x = 0%, 0.1%, 0.3%, 0.5%, 0.7% and 1.0%（atom fraction）） were investigated systemically. Results show that both the grain size and lamellar spacing decrease remarkably with the increase of Y content. When the content of Y is greater than 0.1%, most of the Y elements accumulate along the grain boundaries and some fine particles are uniformly dispersed within the grains in the form of YAl2 compound because of the low solubility and segregation of Y in TiAl alloys. Grain-boundary seg- regation of Y element is more prominent with the increase of Y addition. Good tensile properties are obtained when Y addition ranges from 0.3 % to 0.5 %. The refinement of grain and lamellar structures and dispersion of YAl2 within the grains contribute to the improvement of tensile properties. On the other hand, for high Y-added alloys （over 0.5% Y）, tensile properties are obviously deteriorated due to brittle cleavage fracture of the coarse YAl2 network.     

热处理对锻态2.5vol.%(TiB TiC)/Ti复合材料组织与性能的影响

研究了热处理条件对锻态2.5vol.%(TiB TiC)/Ti复合材料显微组织和力学性能的影响。结果表明：固溶时效处理对复合材料的基体组织特征有显著影响,在两相区进行固溶时效处理后,得到等轴和双态组织,随固溶温度的升高,初生α相含量逐渐降低,而β转变组织含量逐渐升高,当固溶温度超过β转变温度时,得到全片层组织。TiB和TiC增强相在热处理过程中较为稳定,形态与分布无明显变化。固溶时效处理后,锻态复合材料的拉伸强度提高而塑性降低,随固溶温度的升高,复合材料的室温拉伸强度和塑性均有明显增加,而650 oC下拉伸强度与塑性与室温下表现出相反的规律。复合材料经1050oC/2h/AC 600oC/6h/AC处理后综合性能最好,室温拉伸强度为1215.8MPa,延伸率为3.14%,650 oC下拉伸强度为629.9MPa,延伸率为15.9%。     

Ti-10Mo-XNb合金铸态组织和机械性能的研究

为了研究Nb元素对Ti-10Mo合金组织和性能的影响,采用钨电极熔化、离心浇注工艺制备了4种钛合金(Ti-10Mo-XNb,X=0,3,7,10),分析并测试了Nb元素对Ti-10Mo合金铸态组织和力学性能的影响.研究结果表明:随着Nb含量的增加,3种Ti-Mo-Nb合金的铸态组织和相组成发生了改变,Ti-10Mo-3Nb合金由等轴的α+β晶粒组成,Ti-10Mo-7Nb合金由等轴的β晶粒组成,Ti-10Mo-10Nb合金由少量等轴和大量枝状的β晶粒组成.另外,随着Nb含量的增加,3种Ti-Mo-Nb合金的维氏硬度、压缩强度、弹性模量降低,压缩率和抗弯强度升高,压缩断口和弯曲断口由脆性断裂向韧性断裂转变.Ti-Mo-Nb合金有望成为新型的生物医用材料.     

双步球磨法制备纳米晶结构TiAl基合金粉末的研究

以元素粉末为起始粉末,采用双步球磨法(球磨+热处理+球磨)制备TiAl基纳米晶多相结构粉末(粉末成分为Ti-47Al(at%)、Ti-45Al-2Cr-2Nb-1B-0.5Ta(at%)).采用xRD、SEM、EDs、DTA、粒度分布仪对两种粉末颗粒在球磨和热处理过程中的特性进行了表征和分析.结果表明,采用双步球磨法制备的多相结构纳米晶粉末杂质含量低,粒度分布均匀,合金元素弥散分布.一步球磨6 h获得Ti/Al均匀复合结构及实现Ti(Al)部分固溶;700℃,2 h热处理获得Ti3Al、Ti、Al3Ti、TiAl相,Al相已经消失;二步球磨实现晶粒尺寸、颗粒尺寸进一步细化.     

γ-TiA1/TC4复合板材的制备及组织性能研究

提出了制备γ-TiAl/Ti合金复合板材的技术思想.采用包套轧制技术在1150 ℃轧制出厚度为3 mm的Ti-43Al- 9V-0.3Y/Ti-6Al-4V复合板材,其中Ti-43Al-9V-0.3Y合金层的厚度约为2.3 mm,Ti-6Al-4V合金层的厚度约为0.7 mm.复合板材的总变形量为80%.包套轧制后板材外形完整、无应力开裂.分析表明,复合板材的界面相主要由α2-Ti3Al构成.拉伸性能测试结果表明,随着Ti-6Al-4V合金层厚度的增加,复合板材室温下的抗拉强度、延伸率都得到了显著的提高.当Ti-6Al-4V合金层厚度达到0.7 mm时(板材总厚2 mm),室温强度和延伸率分别超过800 MPa和4%,700 ℃条件下延伸率超过25%.     

Microstructures and mechanical properties of TiAl alloy prepared by spark plasma sintering

A fine-grained TiAl alloy with a composition of Ti-47%Al(mole fraction) was prepared by double mechanical milling(DMM) and spark plasma sintering(SPS). The relationship among sintering temperature, microstructure and mechanical properties of Ti-47%Al alloy was studied by X-ray diffractometry(XRD), scanning electron microscopy(SEM) and mechanical testing. The results show that the morphology of double mechanical milling powder is regular with size of 20?40 μm. The main phase TiAl and few phases Ti₃Al and Ti₂Al were observed in the SPS bulk samples. For samples sintered at 1000 °C, the equiaxed crystal grain was achieved with size of 100?250 nm. The samples exhibited compressive and bending properties at room temperature with compressive strength of 2013 MPa, compression ratio of 4.6% and bending strength of 896 MPa. For samples sintered at 1100 °C, the size of equiaxed crystal grain was obviously increased. The SPS bulk samples exhibited uniform microstructures, with equiaxed TiAl phase and lamellar Ti₃Al phase were observed. The samples exhibited compressive and bending properties at room temperature with compressive strength of 1990 MPa, compression ratio of 6.0% and bending strength of 705 MPa. The micro-hardness of the SPS bulk samples sintered at 1000 °C is obviously higher than that of the samples sintered at 1100 °C. The compression fracture mode of the SPS TiAl alloy samples is intergranular fracture and the bending fracture mode of the SPS TiAl alloy samples is intergranular rupture and cleavage fracture.     

喷射共沉积Al-4. 7Cu-1. 73M g/S iCP复合材料的界面微结构和性能

采用TEM 技术分析了喷射共沉积态及挤压态Al-4. 7Cu-1. 73M g/SiC_P复合材料的微观结构及SiC_P 与α-A l 基体等的界面结构, 同时测定了喷射共沉积+ 挤压+ T 6 处理态下该材料的力学性能及耐磨性能。      

大型机床用无锡耐磨青铜的研究

本文在实验室和工厂条件下研究了一种大型机床用无锡耐磨轴承材料,考虑了不同合金元素对该材料的显微组织和力学性能的影响。结果表明,该材料的技术性能指标超过了锡青铜ZCuSn10P1和ZCuSn6PbZn3两种牌号的技术指标。     

Y, Nb对快速凝固TiAl合金组织和性能的影响

研究了元素Y和Nb对用熔体快淬法制备的TiAl基快速凝固合金组织及性能的影响。发现添加Y的快速凝固TiAl合金主要为等轴晶,主要组成相为α2和少量的γ相。随着Y含量的增加,γ相的含量增加,快速凝固TiAl合金的组织逐渐细化。不同Nb含量的快速凝固TiAl合金的组织为块状结构和层片状结构,主要由γ和α2两相组成,层片间距显著细化,为15～17nm。快速凝固TiAl合金的硬度比其铸态合金显著提高。