钛合金与其它金属材料扩散连接研究现状与发展

先进材料钛及钛合金与其它金属材料的扩散连接技术是当前材料连接领域的热点研究课题之一。本综述了钛合金与其它金属材料扩散连接研究现状与发展,重点介绍了钛及钛合金与钢、铜合金、铝及其合金的扩散连接界面反应、连接工艺研究等内容,分析其优势与局限性,并展望其发展趋势。     

Ni-Co纳米镀层为中间层的TC4钛合金低温扩散连接北大核心CSCD

针对钛合金在高温扩散连接时易变形、扩散设备及模具需求苛刻等问题,在TC4钛合金表面电沉积Ni-Co纳米镀层并将其作为中间层,以达到降低扩散连接温度的目的。研究了Co含量对Ni-Co纳米镀层微观组织及性能的影响规律,当Co含量为20 g·L^(-1)时,镀层表面平滑且硬度最高,为537.6 HV,晶粒尺寸最小,为19.2 nm。当镀层厚度为2.5μm、扩散连接温度为800℃时,焊接接头的剪切强度达到543.4 MPa,与不加中间层的焊接试样相比,剪切强度提高了61.4%。Ni-Co纳米镀层作为中间层提高了原子的扩散系数,实现了TC4钛合金在低温、低真空环境中的高质量扩散连接,对工程应用具有重要意义。     

钛及钛合金先进连接技术研究

研究表明,用传统的熔化焊工艺方法焊接钛及钛合金其效果并不理想,故寻求新的有效的先进焊接技术来焊接钛及钛合金己成为近年来的一个研究热点。本文综述了如电子束焊接、激光焊接和扩散连接等先进连接方法用于焊接钛及钛合金所取得的成果,并展望了其在钛及钛合金钛焊接中的应用前景。     

钛合金与不锈钢超塑性扩散连接工艺及机理研究

基于微细晶超塑性扩散连接方法,对TC4钛合金与1Cr18Ni9Ti不锈钢成功实现了直接扩散连接,系统分析了接头性能、界面微观结构及超塑性扩散连接机理。结果发现：TC4钛合金与1Cr18Ni9Ti奥氏体不锈钢直接超塑性扩散连接时,较佳连接工艺规范为：温度T=760~820 ℃,压力p=6~9 MPa,时间t=20~40 min;接头剪切强度τ＝125.3~148.7 MPa。与一般直接扩散连接相比,连接温度降低了约100 ℃,接头的剪切强度提高了1倍以上,且连接试样无明显变形。细化热处理TC4钛合金与1Cr18Ni9Ti不锈钢超塑性扩散连接时,其接头的形成过程大致可分为3个阶段：形成紧密接触阶段、接触表面激活阶段及靠近活化中心的界面冶金结合区形成阶段。     

TA15钛合金超塑成形/扩散连接的可行性研究

采用厚度为2、4 mm的TA15钛合金板材,通过超塑成形/扩散连接的方法制备TA15钛合金重要承力壁板。经宏观及显微镜观察、超声波无损检测发现,该壁板质量良好。制备与超塑成形/扩散连接壁板的材质、厚度、成形工艺及成形过程完全一致的试验件,考核其拉伸性能、疲劳性能、剪切性能。结果表明,采用该种工艺制造的TA15钛合金壁板的力学性能满足设计要求,同时也指出TA15钛合金超塑成形/扩散连接的工艺参数有待进一步优化。     

TA15钛合金超塑及扩散连接性能

TA15钛合金是一种近α型钛合金,具有较好的综合力学性能,最高使用温度可以达到500℃,在飞机和发动机结构中有着广阔的应用前景。通过研究TA15钛合金的超塑性和扩散连接特性,揭示了温度、压力、时间等工艺参数对TA15钛合金超塑成形伸长率和变形后的力学性能、扩散连接接头界面焊合率和微观组织的影响规律,获得了TA15钛合金最佳超塑成形/扩散连接(SPF/DB)工艺参数及其典型结构SPF/DB制备工艺路线。通过制备典型结构件及对其组织和性能分析,验证了采用SPF/DB工艺制备TA15典型结构件的工艺可行性。     

表面纳米化不锈钢与钛合金扩散连接中的扩散系数

采用高能喷丸对0Cr18Ni9Ti不锈钢和TA17近α钛合金棒材端面进行了表面自纳米化处理,在处理表面以下一定厚度内形成了纳米晶组织.利用脉冲加压扩散连接在825℃下对不锈钢和钛合金进行时间为180s的扩散连接,得到了抗拉强度为221.6MPa的扩散连接接头,利用能谱仪(EDS)测试出接头界面两侧一定范围内不同原子的扩散浓度,计算出了Fe原子在TA17近α钛合金扩散层中的扩散系数.结果表明,钛合金与不锈钢经表面自纳米化处理后,在短时间的扩散连接过程中原子扩散系数有所提高.     

表面纳米化对钛合金与钛铝合金扩散连接影响的研究

通过喷丸处理在TC11钛合金表层获得纳米晶,分别对TiAl合金与TC11钛合金、表面纳米化TC11钛合金在不同连接温度下进行扩散连接。利用透射电镜、扫描电镜、电子探针进行组织与元素分析,测试接头的剪切强度。实验结果表明,经过喷丸后TC11钛合金在表层获得厚度为20μm的纳米晶。表面纳米化处理有利于促进扩散中间层的增长,降低最佳扩散连接温度。扩散中间层的厚度对接头剪切强度与断裂方式有较大的影响。钛合金经表面纳米化后,扩散中间层厚度为1.7μm时,剪切强度最高。     

置氢TC4钛合金与TiAl合金的扩散连接研究

分别对Ti Al合金与TC4钛合金、置氢0.5 wt%的TC4钛合金进行了扩散焊接试验。利用扫描电子显微镜、X射线衍射分析仪、能谱分析仪对接头界面进行了分析,并开展了抗剪强度试验。结果表明,在焊接温度为850℃,连接压力为15 MPa的工艺参数下,当保温时间为5 min时,连接界面存在细小孔洞;当保温时间为15 min时,置氢TC4钛合金的界面孔洞消失,并且产生一定厚度的反应层:保温时间达到30 min时,置氢TC4钛合金与Ti Al合金接头的连接强度平均可达290 MPa。断口分析表明,界面组织主要由Ti Al、Ti_3Al、Ti Al_2和Ti_3Al_5相组成。在相同的扩散焊接工艺规范下,置氢TC4钛合金与Ti Al合金的扩散接头连接强度明显高于未置氢TC4钛合金与Ti Al合金的扩散接头连接强度。     

钛合金和不锈钢的扩散焊接研究进展

钛合金和不锈钢的异种金属结构具有广阔的应用前景,但实现其应用的关键是两者可靠的连接。综述了钛合金和不锈钢焊接存在的问题以及国内外扩散焊接研究进展,并提出了进一步的研究方向。     

钛合金与不锈钢扩散焊接研究进展

分析了钛合金与不锈钢的物理化学性能的差异对焊接接头性能的影响,综述了国内外钛合金与不锈钢扩散焊接的研究现状,对钛合金与不锈钢的焊接界面进行表面自纳米化处理后,在扩散焊接过程中能够显著提高原子扩散系数,抑制脆性金属间化合物生长,改善接头组织和提高接头综合性能。展望了钛合金与不锈钢扩散焊接的发展趋势。     

Effect of heating time on bonding interface,atom diffusion and mechanical properties of dissimilar titanium joints produced by thermal self-compressing bonding

Solid-state bonding between pure titanium and Ti6Al4V (TC4) alloy was conducted by a new bonding method named as rigid restraint thermal self-compressing bonding. Effects of heating time on bonding interface, atom diffusion and mechanical properties of the joints were studied. Results show that atom diffusion between pure titanium and TC4 alloy significantly takes place during bonding. The diffusion depths of Al and V in pure titanium side are increased with increasing heating time. Due to the enhancement of atom diffusion, bond quality of the bonding interface is improved along with the increase of heating time. The heating time seems to have little effect on microhardness distribution across the joint. However, the tensile strength and ductility of the joint have close relation to heating time. Prolonging heating time can improve the tensile strength and ductility of the joint, especially the latter. When the heating time increases to 450 s, solid-state joint with good combination of strength and ductility is attained.     

HIP diffusion bonding of P/M titanium alloy Ti-6Al-4V and stainless steel 1Cr18Ni9Ti

The HIP diffusion bonding of P/M titanium alloy Ti-6A1-4V and stainless steel 1Cr18Ni9Ti using pure Ni as intermediate layer was studied. Bonding joint with complex bonding interface was obtained by HIPing pre-alloyed Ti-6Al-4V powders and stainless steel 1Crl 8Ni9Ti in a vacuum canning. The joint strengths were examined and the characteristics of bonding joint were observed. The result shows that the maximized strength of HIP diffusion bonding between P/M titanium alloy Ti-6Al-4V and stainless steel 1Cr18Ni9Ti can be up to 388 MPa and the microstructure of bonding joint is acceptable.     

Impact pressuring diffusion bonding of TA17 to 0Cr18Ni9Ti

Impact pressuring diffusion bonding tests were carried out to produce joint between TA17 titanium alloy and 0Cr18Ni9Ti stainless steel. The reaction products and microstructure near the bonding interface were analyzed. The diffusion of Fe, Cr, Ni and Ti in the bond was revealed by energy dispersive spectroscopy. A number of phases, such as β-Ti, Fe2Ti and σ phases were identified by X-ray diffraction. It was concluded that the bonded joint broke in the region somewhere between Fe-Ti intermetallics and β-Ti during tensile loading. The relationship between bonding parameters and tensile strength of the joint was also determined experimentally, and the optimum time of bonding was only 220 s with 293 MPa joint strength.     

Diffusion bonding of titanium alloy to tin-bronze

The vacuum diffusion bonding of titanium alloy to tin-bronze has been studied and the feasibility and appropriate processing parameters have been investigated. The maximum tensile strength of the joints is bonded joint has been observed by SEM, X-ray and EPMA, and the main factors affecting diffusion bonding have been analyzed. The intermetallic compounds Ti2Cu and TiCu were formed near the interface. The width and quantity of the intermetallic compound increases with the increase of the bonding time. The formation of the intermetallic compounds results in embrittlement of the joint and the poor joint properties.     

Hot spray technology of TA7 titanium alloy coated by molybdenum and its bonding strength

A kind of surface modification test was introduced, by which plasma spray in argon atmosphere with CNC4500 system was applied for TA7 titanium alloy to be coated with molybdenum, and technology to produce metallurgical bonding at interface of coating and base meal was tested by heating in vacuum condition for diffusion after hot spray. With the help of scan electron microscope analysis （SEM）, the effect of argon inlet pressure and heating temperature on coating structure as well as product of diffusion layer were studied. The glued tensile test method was used to measure bonding strength of base metal to coating. The result has shown that both argon inlet pressure and heating temperature exert some effect on coating structure and the width of diffusion layer. A bonding strength of base metal to coating which is greater than molybdenum coating itself may be attained and can be controlled in more than 50 MPa level with tested hot spray technology.     

钛合金化学热处理研究进展

钛合金由于存在致密钝化膜、极高的氧亲和力和较低的原子扩散系数,表面强化很难实现。但钛的碳氮化物及固溶相具备优异的性能,通过渗氮、渗碳、渗硼、渗金属4种化学热处理技术可大幅度改变合金表层组织结构,提高表面硬度和强度。对钛合金化学热处理常用技术特征、渗层微观组织结构、强化机制及力学行为进行了归纳总结,并对未来化学热处理发展前景做了展望。