加工及热处理条件对Ti-26合金组织与力学性能的影响

研究影响Ti-26合金再结晶晶粒尺寸的各种参数,包括冷轧变形量、固溶温度、固溶时间等.变形量10%左右为临界变形量,β晶粒直径随固溶温度、固溶时间增加而增大.还研究了固溶和固溶时效状的β晶粒尺寸对拉伸性能的影响以及冷加工对时效性能的影响.     

形变时效对FeMnSiCrNi合金形状回复率和相变温度的影响

为了进一步提高Fe-14Mn-6Si-8Cr-5Ni合金的形状记忆效应,对固溶态合金采用了形变时效的方法处理,并利用光学显微分析、X射线衍射分析和透射电子显微分析的测试手段分析了时效温度和时效时间对合金形状回复率和相变温度的影响.结果表明,固溶态合金经10%拉伸和600℃时效10 min时,形状回复率提高幅度最大,由固溶态的48%提高到84.7%,并且合金γ→ε马氏体转变的起始温度Ms由固溶态的34℃降低到13.2℃.合金的形状回复率得到提高的主要原因是合金中热诱发ε马氏体已经消失,组织为奥氏体和大量定向α’马氏体,这样的组织特征有利于应力诱发γ→ε马氏体相变以及它们的逆相变.     

固溶温度对VAR制备传感器用Ti-6Ni-3Mo-1Sn合金组织和力学性能的影响

对真空自耗电极电弧熔炼制备的传感器用Ti-6Ni-3Mo-1Sn合金进行热处理,先经过不同温度的固溶处理在经过500℃时效处理4 h,通过实验测试手段研究固溶温度对固溶态和时效态合金组织和力学性能的影响。研究结果表明:固溶温度700℃时,在固溶态合金晶粒中产生了大量初生α相。随着固溶温度增加,形成了更大的β晶粒。以更高温度处理后固溶态合金获得更大拉伸强度以及屈服强度,而伸长率表现为先升高再减小。经过时效处理的时效态合金晶粒中产生了许多弥散态的细小α相。以700℃固溶处理后,形成了初生α相,在残余β相内产生更多β稳定元素。随着固溶温度增加,时效态Ti-6Ni-3Mo-1Sn合金的拉伸强度,屈服强度及伸长率均表现出先增加后减小,最大值发生在固溶温度700℃时,分别为1268,1192 MPa, 5.62%。在低于700℃固溶时效处理后的试样断口区域形成许多尺寸差异较大微孔,呈现脆性断裂特点。     

添加Co对Ti-Ni形状记忆合金组织和性能的影响

以400和600℃退火态Ti-49.8Ni和Ti-49.8Ni-1.0Co合金为对象,用示差扫描热分析仪、光学显微术、X射线衍射仪和拉伸试验研究了添加Co对退火态Ti-Ni形状记忆合金相变、组织和形状记忆行为的影响。结果表明,400℃退火态Ti-49.8Ni和Ti-49.8Ni-1.0Co合金冷却时皆发生A→R→M(A-母相,R-R相,M-马氏体)两阶段相变;加热时Ti-49.8Ni合金发生M→A一阶段相变,Ti-49.8Ni-1.0Co合金发生M→R→A两阶段相变;600℃退火态Ti-49.8Ni和Ti-49.8Ni-1.0Co合金冷却加热时皆发生一阶段AM相变。400℃退火态Ti-49.8Ni和Ti-49.8Ni-1.0Co合金的组织呈纤维状,塑性较差;600℃退火态合金的组织呈等轴状,塑性良好。Ti-49.8Ni合金室温组成相为马氏体,呈形状记忆效应;Ti-49.8Ni-1.0Co合金的室温组成相为母相B2,呈超弹性特性。退火时间对Ti-Ni合金的组织和性能影响不大,合金的相变温度随退火时间延长缓慢升高。形变温度显著影响Ti-Ni合金的超弹性特性,随形变温度升高合金的超弹性应力增加,超弹性滞回面积减小。     

TiNi形状记忆合金阻尼特性的研究

在变频、变温条件下，对两种热处理方式处理的Ti-50．8Ni(原子分数，％)合金的低频阻尼特性进行了研究，结果表明：中温退火处理的Ti-50．8Ni合金的阻尼性能好于高温固溶时效处理的合金；马氏体相、R相阻尼高于母相阻尼，相变过程(多相共存)出现阻尼峰，远远高于母相、马氏体相阻尼，同时伴随有最小弹性模量峰，即相变时材料出现软化现象；相变时阻尼与频率成反比，频率越高，相变阻尼峰越不明显，频率对弹性模量变化几乎没有影响；相变结束合金的阻尼对温度及频率不敏感；中温退火处理的Ti-50．8Ni合金在降温过程中由于温度和应力的复合作用导致多次相变，出现受频率影响的多个相变阻尼峰。     

固溶时效处理对Ni30高温合金组织和性能的影响

为了探究Ni30高温合金的固溶生产工艺,本工作以Ni30高温合金作为研究对象,结合JMatPro数值模拟,对其进行固溶和时效热处理。采用金相显微镜、SEM、EDS和XRD等手段研究了不同固溶温度对Ni30高温合金组织和性能的影响。结果表明：随着固溶温度的升高,合金中的碳化物逐渐溶解,晶粒尺寸逐渐长大,晶粒长大过程符合Arrhenius公式,晶粒长大激活能为74.33 kJ/mol。随着固溶温度的升高,硬度先下降后趋于稳定,最大为41.8HRC;在800℃高温拉伸试验过程中,抗拉强度、屈服强度先上升后下降,拉伸断口基本以韧窝为主,当合金在1 080℃固溶时,经时效处理后抗拉强度值最高为810 MPa,屈服强度值最高为700 MPa。     

时效温度对Ti-51.1Ni形状记忆合金相变和形变行为的影响

用XRD、光学显微镜、TEM、示差扫描量热仪和拉伸试验研究了时效温度(T_(ag))对300、400、500、600℃各保温1h时效态Ti-51.1Ni形状记忆合金组织、相变、拉伸性能和形状记忆行为的影响。结果表明300～600℃时效态Ti-51.1Ni合金室温下由母相B2、马氏体B19′和析出相Ti_3Ni_4组成,显微组织形态呈等轴状,组织中存在Ti_3Ni_4析出相,随T_(ag)升高Ti_3Ni_4析出相的形貌由点状变为片状。随T_(ag)升高,Ti-51.1Ni合金冷却/加热相变类型由A→R/R→A型向A→R→M/M→A型向A→M/M→A型转变(A-母相B2,CsCl型结构;R-R相,菱方结构;M-马氏体B19′,单斜结构);R相转变温度(T_R)升高,M相转变温度(T_M)在500℃时效态后降低。随T_(ag)升高,合金的抗拉强度先升高后降低;伸长率先降低后升高。300、400℃时效态合金呈稳定超弹性(SE),500、600℃呈现形状记忆效应(SME)+SE。要使Ti-51.1Ni合金常温下呈SE,需对合金进行300℃或400℃时效处理;要使该合金在常温下呈SME,需对合金进行500℃时效处理。     

固溶时效对铸造Ti-10V-2Fe-3Al钛合金组织和性能的影响

铸造Ti-10V-2Fe-3Al钛合金为魏氏组织,经固溶时效后,合金组织由晶界α相、初生α相、次生α相及β相组成,其分布特征与固溶温度、冷却速度及时效温度密切相关,合金的拉伸性能随热处理制度变化而变化。     

固溶温度对亚稳β钛合金Ti-4Mo-6Cr-3Al-2Sn的组织和拉伸性能的影响

对自主设计的新型亚稳β钛合金Ti-4Mo-6Cr-3Al-2Sn(%,质量分数)在不同温度进行固溶和固溶时效处理,观察其显微组织和测试室温拉伸性能。结果表明：随着固溶温度的提高固溶态组织中的初生α相减少,当固溶温度高于相变点后初生α相完全消失,几乎全部为明显长大的粗大β晶粒。固溶温度为900℃的固溶态合金具有良好的强度和塑性匹配,屈服强度为898.7 MPa、抗拉强度为962.5 MPa、断裂伸长率为12.7%。在不同温度固溶处理的时效态合金,均析出了细小的次生α相。固溶温度低于相变点时,在初生α相间析出的细小次生α相呈60°或者平行交错排列;固溶温度高于相变点时初生α相几乎完全消失,随着固溶温度的提高析出的次生α相片层间距变大并粗化。在所有固溶温度下,时效态组织中沿原始β晶界处均析出了连续的晶界α相,合金的塑性均较差。经过750℃/0.5 h固溶和500℃/4 h时效的合金具有良好的强度和塑性匹配,其抗拉强度为1282 MPa,屈服强度为1210.6 MPa,断裂伸长率为5.3%。     

热处理制度对Ti-10V-2Fe-3Al组织性能的影响

本文研究了不同固溶和时效温度对Ti-10V-2Fe-3Al合金组织和性能的影响,结果表明,随着固溶温度的升高(700—820℃),组织中的α相含量减少,β相含量增加。时效处理可以提高β基体强度,使材料的强度随固溶温度的升高而升高,塑性下降;随着时效温度的升高(420—620℃),合金的组织成分更加均匀,塑性明显提高,但强度下降。760℃/2h固溶+520℃/8h时效,材料的综合性能最好。     

Tensile properties of a Fe-32Mn-6Si shape memory alloy

The tensile properties of a Fe-32Mn-6Si shape memory alloy were investigated. It was found that tensile properties depend on temperature, heat treatment and material structure. The relationships of martensitic transformation, tensile properties, and shape memory effect are discussed. Finally, we propose a macroscopic one-dimensional constitutive law describing the thermomechanical behavior in tensile loading. Numerically obtained results are close to the experimental ones. __________ Translated from Problemy Prochnosti, No. 2, pp. 55–65, March–April, 2008.     

Intercritical annealing pre-treatment used in a hot-dip galvanised TRIP steel

An intercritical annealing pre-treatment was added before the conventional two-step heat treatment process, and the effect of the isothermal bainitic transformation (IBT) time on the steel's microstructure and mechanical properties were investigated. The microstructure was investigated using scanning electron microscopy, transmission electron microscopy, and X-ray diffraction, while the mechanical properties were evaluated using tensile testing. The microstructure of the three-step hot-dip galvanised transformation induced plasticity (TRIP) steel consists of ferrite, bainite, retained austenite, and martensite. The mechanical properties of the steel after the three-step heat treatment process are excellent, with a tensile strength above 770?MPa and elongation above 29%. The effect of IBT time on the mechanical properties was insignificant because the intercritical annealing pre-treatment increases the bainitic transformation rate.     

退火热处理对TA15钛合金组织性能的影响

研究了不同的退火热处理制度对TA15钛合金显微组织、室温拉伸性能、高温拉伸性能、室温冲击韧性及硬度的影响。结果表明：在相变点以上温度退火,合金具有较高的室温、高温强度,但室温塑性、高温塑性、室温冲击韧性较低;在相变点以下温度退火,合金的室温、高温断裂强度在860℃退火时出现峰值,而室温塑性、高温断面收缩率和室温冲击韧性则随着退火温度的升高而提高;同单重退火相比,双重退火、三重退火对提高合金性能的作用不大。     

Effect of cryogenic treatment on tensile behavior of case carburized steel-815M17

The crown wheel and pinion represent the most highly stressed parts of a heavy vehicle; these are typically made of 815M17 steel. The reasons for the frequent failure of these components are due to tooth bending impact, wear and fatigue. The modern processes employed to produce these as high, durable components include cryogenic treatment as well as conventional heat treatment. It helps to convert retained austenite into martensite as well as promote carbide precipitation. This paper deals with the influence of cryogenic treatment on the tensile behavior of case carburized steel 815M17. The impetus for studying the tensile properties of gear steels is to ensure that steels used in gears have sufficient tensile strength to prevent failure when gears are subjected to tensile or fatigue loads, and to provide basic design information on the strength of 815M17 steel. A comparative study on the effects of deep cryogenic treatment (DCT), shallow cryogenic treatment (SCT) and conventional heat treatment (CHT) was made by means of tension testing. This test was conducted as per ASTM standard designation E 8M. The present results confirm that the tensile behavior is marginally reduced after cryogenic treatment (i.e. both shallow and deep cryogenic treatment) for 815M17 when compared with conventional heat treatment. Scanning electron microscopic (SEM) analysis of the fracture surface indicates the presence of dimples and flat fracture regions are more common in SCT specimens than for CHT and DCT-processed material.     

Effects of thermo-mechanical processing and trace amount of carbon addition on tensile properties of Cu–2.5Fe–0.1P alloys

The effects of thermo-mechanical processing, including intermediate aging treatment and/or solution heat treatment, and a trace amount of carbon (C) addition were studied on tensile behavior of Cu–2.5Fe–0.1P alloys. In this study, Cu–2.5Fe–0.1P alloy sheets without and with a carbon content of 0.05 wt.% were cast and subsequently rolled and thermo-mechanically treated following various processing routes. The introduction of intermediate aging treatment between cold rolling improved the tensile strength of Cu–2.5Fe–0.1P alloys. Solution heat treatment prior to aging was proved to be detrimental on the tensile strength, probably due to recovery and recrystallization causing the complete loss of work hardening during previous cold rolling. The present study also suggested that two-step aging is more effective in improving the strength of Cu–2.5Fe–0.1P alloys than one-step aging. The effect of C addition on improving the tensile strength of Cu–2.5Fe–0.1P alloys was real but marginal, probably due to the limited solubility of C in Cu–2.5Fe matrix. The effects of intermediate heat treatments between cold-rolling processes on tensile properties of Cu–2.5Fe–0.1P specimens with and without C addition are discussed based on optical, scanning electron microscope (SEM) and transmission electron microscope (TEM) micrographs, and SEM fractographs.     

Study of the martensitic transformation in NiTi–epoxy smart composite and its effect on the overall behavior

In this work, the effect of wire phase transformation on the overall thermo-mechanical behavior of NiTi–epoxy composites has been investigated. The shape memory wire received in as drawn condition was subjected to three heat treatments which results to different transformation characteristics. Composite specimens were manufactured by casting followed by curing and post curing process. The mechanical behavior of samples has been determined using standard tensile test. The effect of wire volume fraction and test temperature was investigated as well.It is found that the martensitic transformation occurring in the wire affects the mechanical behavior of the composite specimens. In this way, using the wire with higher transformation stress improves the composite tensile strength. This is achieved either by increasing the test temperature or by using the wires heat treated at lower temperatures. From the experimental results, the martensitic transformation can change the debonding mode. It seems that on the constraint of matrix, the transformation occurs simultaneously at several points in wires that result in regular debonded/undebonded pattern.     

Effect of heat treatment with the mould on the super-elastic property of Ti–Ni alloy castings for dental application

Tensile property of Ti–50.85Ni (mol %) alloy castings was investigated quantitatively in relation to the thermal behavior accompanied with phase transformation to evaluate the effect of heat treatment after casting with the mould in air. The heat treatment temperature was 713 or 773 K, and the period was 0.9, 1.8, or 3.6 ks. Apparent proof stress of the castings decreased with increasing period of heat treatment, and the decrease was larger with the treatment at 773 K. Residual strain also decreased by the heat treatment, however, it was low with the treatment for relatively short period, i.e. 713 K-0.9 and 1.8 ks, and 773 K-0.9 ks treatments. From the thermal behavior measured by differential scanning calorimetry (DSC), the ascent in the transformation temperatures and the increase in the thermal peak height appeared to influence the changes in the tensile property. These changes by heat treatment were believed to be effective to utilize more flexibility, less stress and less permanent deformation in dental castings.     

轧制工艺对低碳中锰钢微观组织和力学行为的影响

目的 研究热轧和温轧两种轧制工艺对低碳中锰钢的微观组织演变和力学性能的影响规律,阐明两种轧制工艺对马氏体转变和应变硬化行为的影响.方法 通过对热轧和温轧两种轧制工艺得到的实验钢进行拉伸性能测试,分析温轧后实验钢强塑性同步提升的现象,通过EBSD数据分析,测量热轧和温轧实验钢中马氏体的转变量,并对两种轧制工艺拉伸后实验钢...     

High-modulus-high-strength poly-(p-phenylene benzobisthiazole) fibres

Heat-treatment processing of dry-jet wet-spun poly-(p-phenylene benzobisthiazole) fibres was undertaken to enhance fibre tensile mechanical properties. The effects of fibre tension and temperature and time of heat treatment in a nitrogen atmosphere on fibre mechanical properties were systematically investigated. Fibres possessing a tensile modulus as high as 300 GPa along with a tensile strength of 3 GPa have been produced. To attain this level of tensile properties, heat-treatment temperatures of 630 to 680° C for residence times of under one minute were required while applying tensions approaching fibre breaking stress at the elevated temperatures; conditions bordered on fibre degradation. Fibre structural changes associated with heat treatment and enchancement of mechanical properties are discussed in Part 2 of this work.     

热处理对碳纤维/聚酰胺6复合材料界面结晶及力学性能的影响

探究了热处理对聚酰胺6（PA6）在碳纤维（CF）表面的结晶行为及其界面力学性能的影响。利用差示扫描量热法（DSC）、偏光显微镜（POM）观察法等分析手段考察了热处理对PA6在CF表面结晶行为的影响,揭示了在热处理过程中,PA6进行链段重排,形成小且不完善的新结晶,导致结晶度的上升以及界面横晶形貌的完善;进一步通过单丝微球脱粘实验和单向CF/PA6复合材料横向拉伸实验考察了热处理对PA6与CF的界面结合性能的影响,揭示了经退火热处理的试样由于弱界面和应力集中的减少使界面剪切强度增加且单位体积断裂能下降。