酸洗对ZTA15钛合金表面污染层及化学成分的影响

利用熔模精密铸造技术制备了ZTA15钛合金试棒。采用金相法观察和测定表面污染层厚度，制定酸洗量。酸洗前后，使用2点直径测量法和金相法确定污染层去除情况；酸洗后进行真空退火，从3种状态试棒表面取样进行化学成分试验，检测氢、氧含量的变化情况，研究了酸洗对ZTA15钛合金表面污染层及化学成分的影响。结果表明，ZTA15钛合金表面污染层厚度为0.1～0.2 mm，当酸洗液中氢氟酸、硝酸和热水按照30%∶30%∶40%的质量比配制、温度40～60℃、酸洗时间60 min以内、酸洗量0.25 mm±0.05 mm时，可以彻底去除硬度高、塑性低的α污染层，避免在后续变形或受力时导致脆化或产生裂纹，提高其使用性能。ZTA15钛合金酸洗后表面有轻微的吸氢，氧含量无明显变化，经真空退火后又有析氢，表面氢含量始终满足<0.01%的要求，不会产生氢脆等对成分性能不利的情况。     

后处理对ZTi60合金材料组织及性能的影响

研究了ZTi60铸造钛合金材料在铸造状态和不同后处理状态下的性能和微观组织。实验结果表明:合金在铸造状态下,存在一定的铸造残余拉应力;经650℃退火处理后,合金的强度和塑性略有提高,硬度HB达到最高,为2 410～2 550 MPa;经热等静压处理后,强度降低,但综合性能有所提高,尤其是冲击吸收功达到最高,为85～94 J;经热等静压+650℃退火后,合金的组织粗化,冲击吸收功显著降低,仅为60～73 J。     

TA10钛合金板材的热处理工艺研究

为了使热轧TA10钛合金板材的塑性指标能够满足后续爆炸复合工艺的要求,对3 mm厚热轧TA10钛合金板材进行了不同温度和不同保温时间的退火热处理,研究退火温度和保温时间对其组织和力学性能的影响。结果表明,热轧态TA10钛合金板材经(700~750)℃×(30~60)min/AC热处理后可以得到较为均匀的等轴α相组织和较好的综合力学性能,满足爆炸复合用钛板的使用要求。     

钛合金粉末热等静压数值模拟及性能研究

利用大型的有限元软件MSC.MARC对钛合金粉末在热等静压(HIP)条件下的变形和致密化规律进行研究,并以典型的TC4(Ti-6Al-4V)粉末为原材料,以数值模拟为工艺指导,进行TC4粉末材料热等静压成形试验,全面分析了热等静压成形的钛合金材料的微观组织和力学性能。结果表明:粉末冶金Ti-6Al-4V微观组织均匀细密,主要有片状α相和相间β相组成,在颗粒与颗粒的交界处,有等轴α相组织的存在,这种特殊的微观组织导致粉末冶金Ti-6Al-4V材料具有不低于锻件的力学性能。     

镦粗变形工艺对TC18组织和性能的影响

研究了不同镦粗变形工艺对TC18钛合金棒材的显微组织和力学性能的影响规律。结果表明,TC18钛合金棒材首先在β单相区加热并施加大变形量锻造,而后在（α＋β）两相区加热并以适当变形量锻造,可获得强度、塑性和韧性等综合性能的良好匹配。     

超塑成形及热处理对TC21钛合金组织演变的影响

TC21钛合金是一种高强高韧高损伤容限钛合金,具有良好的强度塑性断裂韧度和较低的裂纹扩展速率。TC21钛合金的显微组织决定其使用性能和力学性能,通过形变热处理能有效地改善其显微组织,从而达到较好的性能。钛合金的超塑性成形技术是利用材料在超塑性状态下的优异变形性能而发展起来的一种技术。当钛合金处于超塑性状态时其流动性能好,易于填充,从而容易成形出复杂的合     

铸造钛铝合金自生成择优取向层片组织的研究

在离心铸造的Ti-47.5Al-2.5V-1.0Cr(原子分数,%)合金板状试样中得到了整齐对长的柱状晶组织,其内部的α2/γ层片平行于部件的表面.铸造缺陷统计发现,试样中,尤其是心部,存在密度较高的气孔、分散缩松等铸造缺陷.采用热等静压处理可大大降低试样中缺陷的密度和尺度,且热等静压(1250℃,180MPa,3h)处理后其层片组织仍基本保持铸态的择优取向.试验证明,这种经过改善的自生成择优取向层片组织在沿层片的应力作用下具有较好的室温强度和塑性,高温强度较高,缺口增加拉伸强度.     

TA15钛合金大棒与ZTA15精铸件的化学成分波动研究

主要介绍了我国航空ZTA15精铸件用TA15钛合金棒材的20余吨原料试制情况,重点是棒料和铸件的化学成分变化情况,同时分析了大棒的显微组织和力学性能。     

微观组织对TA15钛合金力学性能的影响

比较了两个(α＋β)两相区轧制的TA5钛合金环形件的显微组织和力学性能，分析了两个环形件的工艺控制特征及微观组织对力学性能的影响。结果表明，两相区轧制的TA15合金环形锻件获得了含有等轴初生α相和β转变组织基体的双态组织，等轴初生α相及β转变组织的体积分数和口转变组织中的次生α相的形貌对合金的力学性能有显著影响。等轴初生α相体积分数增加有利于塑性和冲击韧性性能提高，但降低了断裂韧性、持久和蠕变性能。β转变组织体积分数减少且次生α相的球化会显著降低合金抗裂纹扩展的能力，从而降低了高周疲劳性能。     

热加工工艺对TA11钛合金棒材特性的影响

分别采用锻造和轧制工艺得到规格为Ф40mm的TA11钛合金棒材,对比分析了两种加工工艺下TA11钛合金棒材的显微组织、力学性能和超声波探伤结果。结果表明:在本次实验条件下,经轧制的TA11钛合金棒材组织为等轴组织,组织细小,分布均匀。锻造的TA11钛合金棒材显微组织为双态组织,棒材整体组织均匀性较好,但初生α相分布存在局部"群集"的现象;两种热加工工艺得到的棒材力学性能差异不大,均能满足标准要求。轧制棒材探伤杂波水平低于-12d B,可完全满足标准要求;锻造棒材探伤杂波水平不能完全达标。     

Microstructure and mechanical properties of squeeze cast and semi-solid cast Mg–Al alloys

Magnesium–aluminium castings produced by means of squeeze casting, new rheocasting and thixocasting have been investigated. These casting processes provide very different microstructures consisting of α-Mg and β-Mg₁₇Al₁₂. The shape and distribution of the brittle β-Mg₁₇Al₁₂ has a large influence on mechanical properties. Isolated particles of β-phase in squeeze cast components are less detrimental to ductility than the continuous β-phase network found in semi-solid processed parts. A heat treatment results in complete dissolution of β-Mg₁₇Al₁₂ and accounts for significant improvements of ductility and fracture toughness. Crack propagation in solution heat treated Mg–Al castings is associated with extensive twinning.     

The effect of Sr and Fe additions on the microstructure and mechanical properties of a direct squeeze cast Al-7Si-0.3Mg alloy

This article describes the results of an investigation into the microstructure and mechanical properties of a gravity die cast and direct squeeze cast LM25 alloy (Al-7Si-0.3Mg-0.3Fe). The direct squeeze cast LM25 alloy has superior mechanical properties compared to the gravity die cast LM25 alloy, especially with regard to ductility, which is increased from ∼1.7 pct for the gravity die cast LM25 alloy to ∼8.0 pct for the direct squeeze cast LM25 alloy in the T6 heat-treated condition. This increase in ductility is due to (1) the removal of porosity, (2) a decrease in Si particle size, and (3) a refinement of the Fe-Si-aluminide particles. High cooling rates in direct squeeze casting result in quench modification of the Si particles, such that chemical modification with Sr or Na may not be required. In addition, direct squeeze casting is more tolerant of Fe impurities in the alloy, due to the formation of smaller Fe-Si-aluminide particles than those in gravity die cast material. The direct squeeze cast LM25+Fe alloy (Al-7Si-0.3Mg-1.0Fe) has a ductility of ∼6.5 pct, compared to that of ∼0.5 pct for the gravity die cast LM25 + Fe alloy in the T6 heat-treated condition. This increase in tolerance to Fe impurities can lead to a substantial reduction in manufacturing costs due to (1) reduced raw-material costs, (2) reduced die sticking, and (3) improved die life.     

High Temperature Materials Based on the Intermetallic Compound NiAl Reinforced by Refractory Metals for Advanced Energy Conversion Technologies

Advanced NiAl‐based high temperature materials are developed and characterized for structural applications in energy conversion systems. The intermetallic compound NiAl with B2 superlattice structure exhibits superior physical and high temperature mechanical properties, and excellent oxidation resistance. Disadvantages of polycrystalline pure NiAl are the lack in plasticity and fracture toughness at room temperature and insufficient high temperature strength at temperatures above 800 °C. The refractory metals Cr, Mo, and Re form with NiAl quasi‐binary eutectic systems which enable to produce metal fibres reinforced NiAl‐based alloys in the as‐cast condition and by performing directional solidification. These in‐situ composites show fine‐grained and thermally stable microstructures possessing high temperature strength, superior creep resistance and sufficient room temperature ductility.     

Extrusion, Properties, and Failure of Spray-Formed Hypereutectic Al-Si Alloys Based on the Optimization of Fe-Bearing Phase

Based on the densification of the spray-formed hypereutectic Al-Si (hyper-AS) alloys, the microstructural evolution, mechanical properties, as well as the failure are studied in this investigation. The appropriate process and parameters for the densification of the deposits are gained from the thermomechanical simulation. Besides of the spray-formed Al-25Si-5Fe-3Cu (3C) alloy, the microstructures of other spray-formed alloys with Mn/Cr addition are stable without coarsening of the refined α-Al(Fe,TM)Si (TM = Mn/Cr/(Mn+Cr)) particles, which can improve the heat resistance. Especially, a great number of the submicrosized α-Al(Fe,TM)Si phases are observed in the hot-extruded TM-containing alloys. The critical ranges of the major parameter TM/Fe mass ratios that can affect the formation of the α-Al(Fe,TM)Si phases in the cast or spray-formed hyper-AS alloys are severally determined. The structure and lattice constant of the refined α-Al(Fe,TM)Si phases also are characterized. The mechanical properties of the current extruded hyper-AS alloys at room or elevated temperatures are close to or higher than some commercial alloys or other published results. Therefore, the hyper-AS alloys can be proposed as new lightweight, heat-resistant, and high-strength alloys, which can be used in the complex working conditions, such as advanced engine systems. The main reason for the enhanced properties would be the formation of a large quantity of microsized/submicrosized α-Al(Fe,TM)Si phases and abundant dislocations, which can greatly reinforce the matrix and transform the brittle fracture of the needle-like Fe-bearing phases into ductile fracture.     

铜锡合金激光选区熔化非平衡凝固组织与性能

对具有重要工程应用价值的Cu?5%Sn合金进行激光选区熔化（SLM）成形,在激光功率160 W、扫描速度300 mm·s?1、扫描间距0.07 mm条件下,合金样品相对密度可达99.2%,熔池层与层堆积密实,表面质量良好。研究发现所获合金具有非平衡凝固组织特征,其中以α-Cu(Sn)固溶体相为主,且涉及具有超结构的γ相、δ相。显微形貌主要由柱状晶与富锡网状组织构成,伴随有不同尺度界面Sn元素偏析及晶界、晶内纳米尺寸超结构合金相颗粒析出。所获合金的力学性能与同成分铸态合金或较低Sn含量SLM合金相比得到显著强化,表面硬度可达HV 133.83,屈服强度326 MPa,抗拉强度387 MPa及断裂总延伸率22.7%。      

Effects of Mn and Cr contents on microstructures and mechanical properties of low temperature bainitic steel

The effects of Mn and Cr contents on bainitic transformation kinetics,microstructures and mechanical properties of high-carbon low alloy steels after austempered at 230,300 and 350 ℃ were determined by dilatometry,optical microscopy,scanning electron microscopy,X-ray diffraction and tensile tests. The results showed that Mn and Cr can extend bainitic incubation period and completion time,and with the increase of Mn and Cr content,the bainitic ferrite plate thickness decreased and the volume fraction of retained austenite increased. TRIP( transformation induced plasticity) effect was observed during tensile testing which improved the overall mechanical property. The increase of Mn concentration can improve the strength to a certain extent,but reduce the ductility. The increase of Cr concentration can improve the ductility of bainitic steels which transformed at a low temperature. The low temperature bainitic steel austempered at 230 ℃ exhibited excellent mechanical properties with ultimate tensile strength of( 2146 ± 11) MPa and total elongation of( 12. 95 ± 0. 15) %.     

Solidification structure and abrasion resistance of high chromium white irons

Superior abrasive wear resistance, combined with relatively low production costs, makes high Cr white cast irons (WCIs) particularly attractive for applications in the grinding, milling, and pumping apparatus used to process hard materials. Hypoeutectic, eutectic, and hypereutectic cast iron compositions, containing either 15 or 26 wt pct chromium, were studied with respect to the macrostructural transitions of the castings, solidification paths, and resulting microstructures when poured with varying superheats. Completely equiaxed macrostructures were produced in thick section castings with slightly hypereutectic compositions. High-stress abrasive wear tests were then performed on the various alloys to examine the influence of both macrostructure and microstructure on wear resistance. Results indicated that the alloys with a primarily austenitic matrix had a higher abrasion resistance than similar alloys with a pearlitic/bainitic matrix. Improvement in abrasion resistance was partially attributed to the ability of the austenite to transform to martensite at the wear surface during the abrasion process.     

应变速率对全层状TiAl基合金室温拉伸性能的影响

以Ti-47Al-2Cr(摩尔分数,％)合金为对象,研究了应变速率对不同晶团尺寸的全层状TiAl基合金室温拉伸性能的影响.结果表明,全层状TiAl基合金的室温强度随应变速率的加快而提高,低延性全层状TiAl基合金的室温延伸率对应变速率不敏感,而高延性全层状TiAl基合金的室温延伸率对应变速率敏感,并随应变速率的加快而提高.