Ti3Al合金激光焊接接头高温拉伸性能及显微组织

研究Ti-24Al-17Nb合金激光焊接接头的室温及高温拉伸性能,并分析接头显微组织和拉伸断口。研究结果表明,室温下焊缝为单一β/B2相柱状晶组织,室温横向拉伸时接头强度与母材强度相当、塑性有所下降、但仍有25%左右的伸长率,断裂大部分发生在母材部位、少部分断裂在焊缝;高温拉伸时断裂均发生在焊缝部位。高温拉伸时,接头组织发生变化,α2相和B2相向O相转变;焊缝β/B2相向O相转变的切变相变,使原来柱状晶晶界应变集中、容易产生微裂纹,使接头高温强度和塑性明显降低,高温拉伸断口呈现沿晶断裂和解理断裂的脆性断裂形式。     

铁相形貌对铝硅合金高温拉伸断裂机制的影响

研究了不同铁相对铝硅合金高温拉伸性能及其断面显微组织、形貌的影响。结果表明:当合金中铁相形貌呈针状时,合金高温拉伸强度较好,但塑性较差;当合金中铁相形貌呈鱼骨状时,合金高温拉伸强度低于前者,但塑性较好。通过断面显微组织及断口形貌分析可知,含鱼骨状铁相的试样断口为典型塑性断裂特征,而含针状铁相的试样断口为典型脆性断裂特征。裂纹扩展均为沿晶断裂方式。     

Nb在铁基高温合金中的作用

研究了Nb在Fe-Ni-Cr-W-Mo-Ti合金中的中高温强化作用。当Nb含量低于1.22wt-％时,合金的650℃拉伸强度、塑性、持久寿命和疲劳极限随Nb含量升高而提高。Nb促使MC相均匀分布,细化晶粒,增加γ′相的数量和提高其稳定性。当Nb含量为1.22wt-％时,小颗粒Laves相在晶界上弥散析出,有利于合金的综合性能;只有当Nb含量过高时,Laves相在晶界过量析出,才使合金性能恶化。     

硼和碳在一种Ni-Fe-Cr基高温合金中的作用

本文系统地研究了硼和碳对一种Ni-Fe-Cr基高温合金力学性能和组织的影响,发现硼对晶界强化作用比碳大得多,不论固溶硼原子还是硼化物皆可以显著地提高合金的持久强度.添加硼能明显地改善合金的晶界状态和强烈地抑制η等有害相的析出,提高晶界组织稳定性.含0.007％B和<0.04％C时,合金持久性能最佳. 硼和碳对合金的拉伸强度影响不大,但能明显地提高合金的拉伸塑性.为获得良好的拉伸性能,硼和碳含量应分别高于0.002％和0.02％.     

高温持久对Al-Cu-Mg-Ag铝合金的组织和性能的影响

利用透射电镜、SEM形貌观察、剩余强度的测定等试验手段,研究了AlCuMgAg铝合金在欠时效状态下的高温持久对合金的微观组织和力学性能的影响。结果表明,165℃×4h欠时效状态的合金在高温高压持久(200℃、220MPa)条件下,强度逐渐增加,持久时间为20h时,强度达到最大值,而后缓慢下降;持久时间为100h的断裂仍为韧性断裂,只是无析出带的宽度增加。     

Si含量对GH2909合金性能的影响

研究了Si含量对GH2909合金室温拉伸、高温拉伸和持久性能的影响。结果表明:在一定含量范围内,提高Si含量可促进GH2909合金中ε相的析出,有利于降低GH2909合金的缺口敏感性从而提高缺口持久性能。同时Si含量提高降低了GH2909合金的室温、高温拉伸强度,提高了塑性。     

组织形态对近α型TA15钛合金拉伸性能的影响

研究了近α型TA15钛合金组织特征对合金室温和高温拉伸性能的影响,结果表明,300℃以下,试验合金等轴组织拉伸强度高于双态组织,300℃以上则相反;合金中初生d相含量增加,500℃高温拉伸强度降低;次生α片增厚,室温和高温拉伸强度均下降;α相-特别是次生α片的取向一致,500℃高温拉伸强度显著下降.     

DZ951合金的持久性能与断裂行为

研究了定向凝固镍基高温合金DZ951在广泛应力范围(50～970 MPa)内的高温(650～1040 ℃)持久性能.利用SEM观察了持久断裂的断口和变形后的组织结构.结果表明,DZ951合金的持久强度明显高于DZ40M合金,与DZ17G合金相当.温度低于800 ℃时,γ'相形貌基本不发生变化;温度达到900 ℃时,γ'相形成完整的筏型结构.低温(<760 ℃)下合金表现为解理断裂,中温(760～850 ℃)下为解理和准解理混合型断裂,碳化物成为有效的裂纹源.高温(>850 ℃)下合金的持久断裂转变为微孔聚集型断裂,显微疏松成为主要的裂纹源.     

磷对Inconel718形变合金力学性能的影响

对国内生产的低磷Ｉｎｃｏｎｅｌ７１８（Ｐ含量＜０．００１％）及常规Ｉｎｃｏｎｅｌ７１８（Ｐ含量为０．００８％～０．０１３％）形变合金锻件的力学性能进行了对比研究。结果表明,室温拉伸强度和高温拉伸强度的差异不大,然而低磷Ｉｎｃｏｎｅｌ７１８合金的高温塑性和６５０℃,６８６ＭＰａ的持久塑性明显降低;更为值得注意的是,低磷合金在疲劳、蠕变和疲劳／蠕变交互作用下的抗裂纹扩展能力都低于常规合金;而且低磷合金的５９５℃,８９５ＭＰａ缺口周期持久寿命有降低趋势。     

钛合金组织与性能调控工程实例

对比研究了加热温度和冷却方式对现有成熟钛合金牌号组织和力学性能的影响。结果表明,当初生α相数量过多、合金强度较低时,可通过增加一次高温预处理、提高退火温度或增加冷却速率等方式,有效减少合金显微组织中的初生α相数量,实现提高合金的抗拉强度、高温持久强度、断裂韧度的调控目的;当初生α相含量过低、合金塑性与冲击韧度较低时,可通过在两相区控制退火冷却速率来提高初生α相含量,实现提高合金的拉伸塑性、冲击韧度的调控目的。     

Effect of Rare Earth Sc Addition on Microstructure and Mechanical Properties of an Al-Cu-Mg-Ag Alloy

Al-5.3Cu-0.8Mg-0.6Ag alloys containing 0, 0.1, 0.3 and 0.5 (mass. %) Sc were prepared by ingot metallurgy and thermomechanical treatment. The effect of Sc addition on the precipitation and microstructure of the alloys has been investigated using mechanical testing, optical microscope, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It has been shown that trace Sc element refines the grains of the casting alloys and the average grain size decreases from 85 μm to 30 μm. Increasi...     

600MPa级高Al冷轧双相钢点焊接头断裂方式

通过拉伸剪切试验以及对拉剪断口的微观组织和扫描电镜分析,研究了高Al冷轧双相钢点焊接头的断裂方式,并分析了接头断裂方式对接头力学性能的影响规律.研究结果表明,高A1冷轧双相钢的点焊接头主要有3种断裂方式,即:母材撕裂的焊点拔出、沿熔核边界的焊点拔出及界面断裂.3种不同的断裂方式分别代表了3种不同的裂纹萌生和扩展方式.此...     

Effect of T6-treatments on microstructure and mechanical properties of forged Al-4.4Cu-0.7Mg-0.6Si alloy

Transmission electron microscopy (TEM), scanning electron microscopy (SEM), hardness tests and tensile tests were performed to investigate the effect of aging on microstructure and mechanical properties of forged Al-4.4Cu-0.7Mg-0.6Si alloy. The results show that the alloy exhibits splendid mechanical properties with an ultimate tensile strength of 504 MPa and an elongation of 10.1% after aging at 170 °C for 16 h. With tensile testing temperature increasing to 150 °C, the strength of the alloy declines slightly to 483 MPa. Then, the strength drops quickly when temperature reaches over 200 °C. The high strength of the alloy in peak-aged condition is caused by a considerable amount of θ′ and AlMgSiCu (Q) precipitates. The relatively stable mechanical properties tested below 150 °C are mainly ascribed to the stability of θ′ precipitates. The growth of θ′ and Q precipitates and the generation of θ phase lead to a rapid drop of the strength when temperature is over 150 °C.     

Corrosion performance and mechanical properties of sputter-deposited MgY and MgGd alloys

Films of MgY and MgGd alloys were deposited on silicon wafers by magnetron sputtering. The microstructure, crystal structure and mechanical properties were evaluated using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and tensile testing. Corrosion was evaluated for immersion in 3.5% NaCl solution saturated with Mg(OH)₂. TEM, SEM and XRD indicated that the alloys were single phase. There was no significant change of corrosion rate with alloy content. The strength increased with alloying content, and ductility decreased concomitantly. Strengthening was consistent with solid solution strengthening or short-range order.     

7050高强铝合金铆钉丝材T73双级时效工艺

针对国产7050高强铝合金铆钉丝材,采用室温拉伸、室温剪切、镦粗试验的方法,研究了经177～182℃不同二级时效时间后7050铝合金丝材的性能。利用扫描电镜(SEM)、透射电镜(TEM)观察合金不同时效工艺下断口组织和析出相形貌特征。结果表明,拉伸强度和剪切强度随二级时效温度的升高、二级时效时间的延长逐渐降低,剪切强度低于330 MPa时镦粗试样不开裂。TEM微观组织显示,随二级时效温度的升高、时间的延长析出相形貌变化不大,但析出相的尺寸随时效温度的升高逐渐长大、间距逐渐增大;拉伸断口形貌显示,二级时效的断裂方式均为韧窝断裂和沿晶断裂的混合断裂模式,随二级时效温度的升高和保温时间的延长,断口中韧窝数量逐渐增加且尺寸变大,沿晶断裂逐渐减少。     

轧后冷速对X120管线钢组织和强度的影响

研究了X120管线钢模拟控扎后冷却速度对组织性能的影响。扫描（SEM）和电子背散射衍射（EBSD）观察结果表明,提高控轧后冷速可以得到有效晶粒尺寸细小的板条贝氏体,有利于提高大角度晶界百分比,并结合力学性能测试结果,得出细小的板条贝氏体和大角度晶界有利于提高管线钢强度。利用透射电镜和能谱分析研究了实验钢中Nb、Ti等微合金元素的析出规律,冷速越大析出相粒子越细小弥散,沉淀析出强化效果越好。细晶强化、晶界强化和析出相强化等都是管线钢强化的主要方式。     

Effect of Y content on microstructure and mechanical properties of 2519 aluminum alloy

The effects of yttrium（Y） content on precipitation hardening, elevated temperature mechanical properties and morphologies of 2519 aluminum alloy were investigated by means of microhardness test, tensile test, optical microscopy（OM）, transmission electron microscopy（TEM） and scanning electron microscopy（SEM）. The results show that the tensile strength increases from 485 MPa to 490 MPa by increasing Y content from 0 to 0.10%（mass fraction） at room temperature, and from 155 MPa to 205 MPa by increasing Y content from 0 to 0.20% at 300 ~C. The high strength of 2519 aluminum alloy is attributed to the high density of fine 0＇ precipitates and intermetallic compound AICuY with high thermal stability. Addition of Y above 0.20% in 2519 aluminum alloy may induce the decrease in the tensile strength both at room temperature （20 ℃） and 300℃.     

相对挤压比对Al-Zn-Mg合金构件不同部位组织和性能的影响

采用全谱直读光谱仪、X射线衍射技术、拉伸试验测试方法和光学显微镜、扫描电镜、透射电镜、能谱仪观察方法,研究了相对挤压比对Al-Zn-Mg合金构件不同部位热处理前后微观组织和性能的影响.结果表明:挤压态和时效态构件中都存在Al3(Zr,Ti)粒子.相对挤压比越大,Al3(Zr,Ti)粒子含量越高,对热处理过程中再结晶抑制...     

Al—Zn—Mg—Cu—Zr（-Sn）合金的强度和疲劳断裂行为

通过拉伸试验和疲劳裂纹扩展试验研究了Al-Zn—Mg—Cu-Zr（--Sn）合金的强度和疲劳断裂行为。运用光学显微镜（0M）、扫描电镜（SEM）和透射电子显微镜（TEM）对试验合金的微观组织进行分析检测。结果表明,Sn的添加可以阻碍固溶时Al-Zr-Mg-Cu-Zr合金晶粒的长大,也使得过时效Al-Zr-Mg-Cu-Zr-Sn合金的晶界无沉淀析出带（PFZ）变窄及晶界析出相变小,因此,提高了合金的抗疲劳裂纹扩展能力。此外,过时效的Al—Zn—Mg—Cu—Zr-Sn合金具有较高的抗拉强度。     

Microstructure and properties of hydrogenated TB8 alloy

Thermohydrogen processing can enhance workability, decrease flow stress and deforming temperature of titanium alloys. In this study, thermohydrogen processing was carried out for metastable b-type TB8 alloy. The microstructures of hydrogenated TB8 alloy were investigated based on scanning electron microscopy(SEM), transmission electronic microscopy(TEM) as well as X-ray diffraction(XRD) analysis. The results reveal that d hydride phase forms in the hydrogenated TB8 alloy, but the amount of b phase increases with hydrogen content increasing. Single b phase appears when the hydrogen content reaches 0.7 wt%. The alloying elements redistribute in the hydrogenated TB8 alloy, and hydrogen leads to the reduction of the alloying elements in b phase. The room-temperature compression tests were performed on a MTS809 machine. It is found that the room-temperature yield strength of hydrogenated TB8 alloy decreases. And minimum yield strength is obtained at a hydrogen content of 0.5 wt%. The ductility does not decrease within 0.7 wt%hydrogen content. These results provide theoretical basis for improving the formability and promoting the applications of TB8 alloy.