BaZrO3坩埚的制备及与钛合金熔体的界面反应

以BaCO3和ZrO2为原料,采用固相法合成BaZrO3粉体,利用冷等静压成型技术结合固相烧结技术制备出BaZrO3坩埚,并将其用于TiNi合金真空感应熔炼实验。通过研究不同BaCO3和ZrO2摩尔比条件下合成产物的物相组成,分析了烧结温度和助熔剂TiO2对BaZrO3坩埚致密度及熔炼后界面反应的影响。结果表明,在BaCO3和ZrO2摩尔比接近1:1、BaZrO3粉体合成温度为1200℃、TiO2添加量(质量分数)为2%、烧结温度为1750℃条件下,坩埚致密度达到97%。将此坩锅用于TiNi合金熔炼实验,发现BaZrO3与TiNi合金熔体润湿性较差,二者间无过渡层,坩埚材料未向熔体扩散,也没有与BaZrO3反应生成中间相。     

掺杂CaO对BaZrO_3坩埚制备及其与钛合金界面反应的影响

用BaCO_3、ZrO_2和CaO混合粉料,在1400℃经高温固相反应合成了BaZrO_3和CaO掺杂BaZrO_3粉料,采用冷等静压结合固相烧结技术,在1750℃烧成BaZrO_3和CaO掺杂BaZrO_3坩埚,并熔炼Ti2Ni合金,研究了CaO对BaZrO_3坩锅微观组织及其与钛合金界面反应的影响。结果表明:掺杂量为15%(摩尔分数)的CaO部分固溶进BaZrO_3,坩埚在烧成过程中,过量CaO部分在坩埚内部团聚,阻碍Ba_(1-x)Ca_xZrO_3晶粒的生长,导致坩埚内部出现较大孔洞;另一部分在坩埚壁析出,析出层主要由CaO和Ba_(1-x)Ca_xZrO_3组成,厚度约为70μm。BaZrO_3坩埚与钛合金界面反应层厚度约为270μm,而CaO掺杂BaZrO_3坩埚与合金并无明显界面反应层。     

TiNi合金熔炼的耐火材料研究

对石墨、氮化硼(BN)、CaO和CaZrO3等耐火材料与TiNi合金的界面反应开展了系列研究.通过扫描电子显微镜,能谱仪和电子探针对反应界面的形貌和成分进行了分析.结果表明,作为熔炼TiNi合金用耐火材料,按照稳定性排序,依次为CaZrO3CaOBN.用石墨作为熔铸TiNi合金的耐火材料,每炉次的增碳量约为0.02%(ω).     

高活性钛熔体与BaZrO_3耐火材料界面反应机理

利用BaZrO_3坩埚结合感应加热技术熔炼钛合金,通过光学显微镜、扫描电子显微镜、X射线衍射仪以及原子发射光谱仪等分析了BaZrO_3耐火材料与熔体接触后微观形貌变化及BaZrO_3耐火材料与合金之间的相互熔解量,研究了BaZrO_3耐火材料与熔体界面的反应、组成元素在熔体中熔解量随接触时间变化规律及与钛熔体界面反应机理。结果表明:熔炼低含钛量的钛合金,BaZrO_3耐火材料渗透层厚度约为20μm,随着BaZrO_3耐火材料与熔体接触时间增加,氧元素在熔体中熔解量逐渐降低,锆含量则并未出现明显变化,说明BaZrO_3耐火材料不与钛熔体发生界面反应;熔炼高含钛量钛合金时,BaZrO_3耐火材料侵蚀层厚度约为2 000μm,锆和氧在熔体中熔解量逐渐升高,说明高钛含量熔体与BaZrO_3耐火材料发生界面反应,反应过程中有BaO生成。     

添加CaZrO_3或ZrO_2+CaCO_3对再生镁质浇注料性能的影响

基于选用添加剂改善再生镁质耐火材料使用性能的设想,以粒度为5~3和3~1 mm的用后MgO-C钢包内衬砖再生颗粒料,5~3、3~1、1和0.074 mm的MS-95烧结镁砂为主要原料,硅灰为结合剂,三聚磷酸钠为分散剂制备的再生镁质浇注料,研究了分别添加质量分数为0、5%、9%和13%的CaZrO_3或ZrO_2+CaCO_3对不同温度处理后试样性能、物相组成和显微结构的影响的影响。结果表明:随着添加CaZrO_3或ZrO_2+CaCO_3用量的增加,110℃保温24 h和1 000℃保温3 h热处理后试样的线收缩率、显气孔率分别呈现出无明显变化和增大的趋势;1 500℃保温3 h烧后试样的线收缩率、显气孔率和常温抗折强度分别呈现出增大、减小和先增大后减小的趋势。CaZrO_3提高试样的抗钢渣侵蚀性,ZrO_2+CaCO_3降低试样的抗钢渣侵蚀性。与ZrO_2+CaCO_3相比,适量的CaZrO_3可明显提高再生镁质浇注料试样的烧结性能和抗钢渣侵蚀性。引入13%(w)的CaZrO_3,可获得烧结性能和抗钢渣侵蚀性能良好的再生镁质浇注料。在高温且含有SiO_2、MgO及Mg_2SiO_4的条件下,CaZrO_3不能稳定存在;经Mg2+、Si4+与Ca2+、Zr4+间的互扩散可反应形成c-ZrO_2和CaMgSiO_4,CaMgSiO_4相多分布于MgO相和c-ZrO_2相之间。     

烧结CaO的粒度对氧化钙质耐火材料抗水化性的影响

氧化钙被认为是一种热力学性能稳定的且性能优异的碱性耐火材料,尤其适用于真空或还原气氛下的二次炼钢工艺.然而,CaO在空气中易水化,限制了它的应用.本研究在1 600～1 650℃温度范围内利用二步煅烧法提高烧结CaO的抗水化性.第1步,在煅烧过程中,通过最佳温度的选择、急冷以及水化研制出高活性CaO.第2步,通过加入稳定的过渡金属氧化物和稀土氧化物添加剂,研制出高致密烧结CaO,且烧结CaO的粒度范围在80～120μm.50℃、相对湿度为92%的条件下检测烧结CaO的水化程度,时间为3h.结果显示,水化增重达到1.5%.利用烧结CaO制备的耐火砖在1 600～1 650℃温度内烧成.研制的氧化钙耐火材料的荷重软化温度为1 730℃.另外,由于烧结CaO的品粒尺寸较大以及与熔渣接触的晶界面积较小,预计可提高抗二次精炼的侵蚀性.该氧化钙耐火材料除了具有优异的高温性能外,在空气中保存1个月强度却没有降低.当氧化钙耐火材料(没有任何涂层)用塑料袋包装时,其保存时间可以提高到90天.     

转炉钢渣热态改性对镁质耐火材料的侵蚀行为

以镁质坩埚为试验容器,配制碱度分别为1.2、1.5、1.7、1.9、2.2、2.4的改性钢渣并放置于坩埚中,以10℃.min-1的速率升温至1 570℃并保温30 min加热熔化。研究了热态改性钢渣对镁质坩埚的侵蚀,并采用光学显微镜、SEM、EDS和XRD进一步分析了侵蚀行为。分析表明:改性钢渣对镁质耐火材料的侵蚀反应主要在熔渣-坩埚界面处进行,熔渣碱度≤1.5时耐火材料侵蚀加重;由于钢渣中铁离子渗透进方镁石晶体内,形成弥散分布的颗粒状富FeO固溶体和含FeO方镁石基质相,这两种物相受内部FeO、MgO质量比和钢渣中Al2O3含量的影响,选择性地同渣中不同化学组分进行反应而脱落溶解至钢渣中。     

BaZrO3/Al2O3复合模壳水化损毁机理及其对定向凝固TiAl合金的影响

以BaZrO3为面层材料和Al2O3为背层材料,在1600℃保温8 h烧结制备BaZrO3/Al2O3复合模壳.通过光学显微镜、X射线衍射仪、扫描电子显微镜结合能谱仪等手段观察了面层与背层界面结合层水化前和水化后的物相与显微结构变化,分析了模壳内界面结合层的水化过程及损毁机理,并通过TiAl合金定向凝固实验,研究了模壳...     

氧化烧结Si3N4／SiC复合材料的抗冰晶石侵蚀性能研究

采用坩埚法研究了氧化烧结氮化硅结合碳化硅复合材料的抗冰晶石熔体侵蚀的性能,并利用X射线衍射仪(XRD)和场发射扫描电镜(FE-SEM)对坩埚侵蚀层进行了成分和形貌分析.结果表明,氧化烧结制备的Si3N4/SiC坩埚在1 000℃,空气介质中,经20h冰晶石熔体侵蚀处理后,坩埚内壁仅有少量腐蚀残留,具有良好的抗冰晶石熔体侵蚀性能.     

钛合金熔模精密铸造用氮化硼基复合型壳的探索试验

研究了六方氮化硼作为钛合金熔模精密铸造中面层造型材料的可行性.以高温高压下预处理的氮化硼作为型壳面层中的主要耐火材料,钇溶胶作为黏结剂并适当加入少量氧化钇,制备氮化硼基复合型壳.研究了氮化硼涂料的密度、黏度等性质,通过热重分析探讨了氮化硼基复合型壳的烧结工艺.研究表明:面层涂料具有剪切稀释性,涂料的表观黏度随剪切速率的升高而降低.当型壳焙烧温度高于800℃时应采用N2保护加热.TiNi合金与型壳的反应较小,在TiNi合金铸件中没有出现夹杂氧化钇颗粒.     

Microstructure and joining strength evaluation of SiC/SiC joints brazed with SiCp/Ag–Cu–Ti hybrid tapes

SiC particulates were mixed with Ag–Cu–Ti powders to fabricate SiC_P/Ag–Cu–Ti (SICACT) sheets by tape casting process, which were used to braze the sintered SiC ceramics with the structure of SiC/Ag–Cu–Ti foil/SICACT sheet/Ag–Cu–Ti foil/SiC. Microstructure and joining strength both at room temperature and at high temperature were characterized by electron probe X-ray microanalyzer, electron dispersive spectroscopy, transmission electron microscopy, and flexural strength test. The SiC particulates from the SICACT sheets were randomly distributed in the filler alloy matrix and reacted with Ti from the filler alloy. Reaction products TiC and Ti₅Si₃ were found in the interfacial reaction layer. With the increase in SiC particulates volume fraction, the joining strength at room temperature first increased, and then decreased, which was affected by both CTE mismatch and the thickness of the reaction layer. In addition, the joining strength of joints brazed using SICACT sheets at 600?°C can reach 197 MPa, which was obviously higher than that brazed using Ag–Cu–Ti filler alloy.     

Corrosion resistance of calcium zirconate crucible to titanium-copper melts

The corrosion resistance of refractory materials to the titanium alloy melts is vital for the production of titanium alloys by vacuum induction melting. In this study, the corrosion behavior of calcia-stabilized zirconia, solid state synthesized calcium zirconate, and fused calcium zirconate refractory suffering Ti-5 wt% Cu melts were investigated at 1680 ℃ for 15 min of soaking time by the cup test method. It was found that the three crucibles directly dissolved into the titanium melt, then generated Ti (Zr, O) and CaZrO₃ in the infiltration layer, and eventually developed a porous Ti₃O layer in the lining. Besides, the contamination of Ti-5 wt% Cu alloy (oxygen: 5.3 wt%; zirconium: 6.01 wt%; calcium: 0.42 wt%) by fused calcium zirconate crucible was significantly less than the solid state synthesized one (oxygen: 5.83 wt%; zirconium: 6.14 wt%; calcium: 0.43 wt%), implying that the production method of calcium zirconate notably affected the impurity of titanium alloys.     

A novel potential ceramic material for melting Ti6Al4V alloy: A solid solution of BaZrO3 and CaZrO3

Vacuum induction melting technology is a promising low-cost method for producing high-quality titanium alloy. The key challenge lies in the development of ceramic crucibles with excellent chemical stability for titanium alloy corrosion. In this work, (Ba_1−x,Ca_x)ZrO₃ ceramic was designed and synthesised via pressureless sintering of a mixture of BaZrO₃ and CaZrO₃ powders. X-ray diffraction and scanning electron microscopy analyses showed that a new phase, Ba_0.8Ca_0.2ZrO₃, was formed after heat treatment at 1700 °C. Vacuum induction melting experiments of the Ti6Al4V alloy were carried out using a Ba_0.8Ca_0.2ZrO₃ crucible. Compared with the original BaZrO₃ crucible and CaZrO₃ crucible, the erosion layer of the Ba_0.8Ca_0.2ZrO₃ crucible was significantly reduced by approximately 85∼92.5%. The interface between the crucible and the alloy was clearly visible, and there was no obvious element diffusion between the alloy and the material. This shows that Ba_0.8Ca_0.2ZrO₃ is highly promising as a crucible material for melting Ti6Al4V alloys.     

BaZrO3 refractory crucibles for vacuum induction melting of industrial Zr-based bulk metallic glass master alloys with Y addition

The absence of appropriate melting method and expensive cost of high-purity Zr raw material limit the commercial application of Zr-based bulk metallic glass. In the present study, using high oxygen industrial grade sponge Zr as raw material and the metal Y as additive, the low-cost and high-purity master alloys were successively prepared using a VIM method with a BaZrO₃ refractory crucible. The results indicate that the BaZrO₃ refractory exhibited good erosion resistance to the alloy melt, the Y additive formed the Y₂O₃ barrier layer on the surface of crucible, which prevented the melt permeation into the crucible, then effectively reduced the thickness of the erosion layer. In addition, the metal Y deoxidizer could remove the oxygen of melts, finally the low oxygen Zr-based master alloy (about 0.02 wt%) was prepared. These results may provide a promising preparing technique prototype of low-cost Zr-based bulk metallic glass.     

Effects of Ti thickness on microstructure and mechanical properties of alumina–Kovar joints brazed with Ag–Pd/Ti filler

Alumina, metalized with Ti by magnetron sputtering, has been successfully bonded to a Kovar alloy using Ag–5 wt% Pd filler. The effects of Ti content on the interfacial microstructure and mechanical properties were investigated. The results showed that a reaction layer was formed at the alumina/filler interface. Microanalysis indentified the reaction products to be titanium oxide and Pd–Ti compounds. The thickness of the reaction layer and the residual filler layer played determinable roles on the joint strength. The maximum four-point flexural strength of the brazed joints at room temperature reached as high as 177.3 MPa when the thickness of Ti layer was 3 μm.     

全四方TZP—ZrO2直简坩埚制备技术的研究

实验对全四方TZP-ZrO2敞粉进行激光粒度分析．结果表明颗粒粒度小于20μm。用该微粉做烧成试验．烧成温度分别为1450℃、1490℃、1530℃、1570℃、1610℃、1650℃。X射线衍射分析结果表明．烧成后试样的晶型为四方相ZrO2;镜结果表明．晶粒尺寸为0．9μm．试样相对理论密度为99%．抗折强度为502．44MPa．硬度为1484．37kg／mm^2断裂韧性为11．6MPa·m^12,耐磨性（利用TLM耐磨性能测定仪测定）在1610℃烧成的试样耐磨性最佳．为24．77mm^3．利用热压注成形制得ZrO2坩埚。     

Evaluation of Ca-doped BaZrO3 as the crucible refractory for melting TiAl alloys

In this study, a new Ca-doped BaZrO₃ refractory was designed by using thermodynamics approaches and tested for its applicability for vacuum induction melting (VIM) of TiAl alloys. The influence of CaO on the BaZrO₃ phase constitution and microstructure, as well as the key features of the TiAl melt interaction with the Ca-doped BaZrO₃ crucibles were investigated by X-ray diffraction (XRD), optical microscopy (OM) and scanning electron microscopy (SEM). Results revealed that the Ca-doped BaZrO₃ refractory consisted of Ba_1-xCa_xZrO₃ and CaO phases. An obvious interaction occurred during the melting of the TiAl alloy in the Ca-doped BaZrO₃ crucible along with the generation of BaAl₂O₄ as a reaction product, with formation of a reaction layer up to 5?µm thick. Dissolution of Ca-doped BaZrO₃ refractory in the TiAl melt was the main reason for the alloy-crucible reaction. Moreover, the Ca-doped BaZrO₃ crucible was found to substantially reduce the contamination of the TiAl alloy, with lower oxygen concentration as compared with other conventional oxide crucibles. Overall results confirmed that vacuum induction melting using the Ca-doped BaZrO₃ refractory can be considered as an appropriate method for the fabrication of TiAl alloys.     

微波烧结SiC-Cu/Al复合材料的工艺及机理

用微波烧结工艺成功制备了铜包裹碳化硅颗粒增强铝基(SiC-Cu/Al)复合材料,利用扫描电镜和X射线衍射分析仪对烧结样品进行表征,并讨论了烧结过程及机理.研究表明:采用多晶莫来石纤维棉、硅碳棒和氧化铝坩锅组合设计的保温结构能很好地促进烧结.烧结温度为720℃时,SiC-Cu/Al复合材料的密度取得最大值为2.53g/cm3.SiC-Cu/Al复合材料的硬度随烧结温度的升高的变化成马鞍状.烧结温度对样品显微结构的影响较大,随着烧结温度的升高,相分布的均匀性降低,在较高的烧结温度下会出现SiC颗粒的偏聚.涡流损耗和界面极化损耗是促进微波烧结的主要动力.     

Hydroxyapatite reinforced with Ti–Fe particle: correlation between composition,microstructure and mechanical properties

Abstract

Composites of hydroxyapatite (HA) with 5 wt-% Ti–Fe reinforcing particles were pressureless sintered in vacuum at a temperature range between 950 and 1100°C. It was found that although the decomposition of HA and interaction between HA and Ti occurred, the desirable Ti phase still remained in the composites sintered at all temperatures. The outer Ti shell thickness of the distinctive core–shell Ti–Fe particles was observed to become larger as the sintering temperature increased. It was also found that minor pores appearing near the interface were beneficial to obtain appropriate interfacial bonding between HA matrix and Ti–Fe particles. The composite sintered at 1050°C exhibited superior flexural strength, fracture toughness, and fatigue resistance owing to the remained Ti phase and dense microstructure as well as good interfacial bonding.     

不同原料体系对无压烧结合成Ti3SiC2的影响及其腐蚀行为

通过液相磁力搅拌混合原料粉末,压片后无压烧结合成了三元Ti3SiC2,研究不同原料配比Ti/Si/C,Ti/SiC/C/和TiC/Si/Ti对合成Ti3SiC2的影响,同时为了比较,在相同条件下加入少量Al或Sn,研究其对Ti3SiC2的合成过程及最终产物的影响,并探讨Ti3SiC2的合成机理.结果表明:3Ti/1.2Si/2C/0.1Al在1400 ℃无压烧结合成了较高纯度的Ti3SiC2,Al粉的加入可以降低混合粉末的起始反应温度,有利于三元层状化合物Ti3SiC2的合成和纯度的提高,其合成机制为,在铝粉形成的熔池中,经形核钛和硅反应生成钛硅金属间化合物,钛与石墨反应生成碳化钛,随后扩散,长大,随着温度的升高,反应生成三元层状Ti3SiC2.而以TiC或SiC为Ti或Si源制备的Ti3SiC2含杂质较多,不适用于无压烧结合成Ti3SiC2.合成的Ti3SiC2在HF溶液中经200 ℃溶剂热反应后,产物主要为两种不同晶型的SiC和AlF3立方体,且随着反应时间的延长,AlF3的含量增加,结晶更完善.