TC18钛合金的组织和性能与热处理制度的关系

通过三因素三水平正交设计方法研究了两阶段退火热处理制度的三个温度阶段对TC18钛合金性能、组织的影响,定量分析了合金热处理温度变化对总体性能的影响,结果表明,在本文试验条件下可通过提高中温温度、降低低温温度来提高合金的强度,降低高温温度、提高低温温度可改善合金的塑性,通过降低高温温度或中温温度可提高合金的冲击韧性,显微组织分析表明,TC18钛合金的强度主要受未转变β组织及在其上产生的次生αs相的总的含量、次生αs相的含量、形状的控制;合金的塑性受初生αp相形状及次生αs相的数量、形状控制;合金的冲击韧性受初生αp相的含量及形状控制.     

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。     

钼钨含量和热处理对一种高温钛合金拉伸性能的影响

研究了具有不同β相稳定化元素(Mo,W)含量的TMW-1(K_β=5.5)钛合金和TMW-2(K_β=3.5)钛合金,经不同双重和三重退火处理后的室温和650℃高温拉伸性能。结果表明:经适当的热处理,在不损害室温塑性的情况下,TMW-1钛合金和TMW-2钛合金在650℃的拉伸性能均能达到近α钛合金在600℃的拉伸性能。为了保证合金650℃的拉伸性能,合金中β稳定化元素(Mo,W)含量应使β稳定化系数K_β保持在3.0-3.5为宜。     

Zn—4%Al合金超塑性变形性能及添加Cu、Mg的影响

本文研究了Zn—4％Al合金的超塑性拉伸性能,板材成型性以及合金元素Cu、Mg对上述性能的影响。结果表明:在350℃以下的温度区间和1.38 ×10~(-3)/s以上的应变速率区间内,该合金的延伸率随温度的升高和应变速率的降低而提高;合金元素Cu、Mg可同时提高该合金的超塑性变形性能和室温强度;经超塑性变形后合金的室温强度明显提高。     

耐低温冲击高强高韧合金的组织与性能

高强高韧合金铸钢具有优良的力学和物理化学性能,使得其具有巨大的发展潜力和经济效益。通过合理的成分设计及热处理工艺,获得制备工艺简单、强韧性高、成本低、污染小,且具有良好低温韧性、焊接性的低合金已成为一项技术问题。本工作针对奥氏体-马氏体高耐蚀高强度合金,通过成分与热处理的良好匹配,使合金达到优良的强塑性。对合金组织和性能进行分析,得出影响合金力学性能的主要因素,为大批量制备该合金打下坚实的基础。通过试验结果可知:相同回火温度下,随着碳含量的增加,合金的室温拉伸强度升高,塑性下降;相同碳含量下,回火温度从480℃升高到540℃,室温拉伸强度先升高后降低,在520℃下达到峰值1 552 MPa,冲击韧性先升高后降低,在500℃时达到最大值54 J·cm~(-2)。合金热处理冷却方式由空冷调整为油冷后,其强度和塑性大幅提高,室温拉伸强度达到1 580 MPa,冲击韧性达到100.6 J·cm~(-2)。     

退火温度对冷轧Ti-13V-3Al-0.5Cu形状记忆合金组织结构与马氏体相变的影响

使用XRD、TEM、DSC和室温拉伸等分析测试手段,对冷轧后经不同退火温度处理的Ti-13V-3Al-0.5Cu(%,原子分数)合金微观组织结构,马氏体相变行为,力学性能和形状记忆性能进行了研究。经冷轧、退火处理后,合金在室温下的组织主要为α"马氏体相,存在少量残余β母相、α相和Ti₂Cu第二相。随着退火温度的增加,合金形状记忆性能先升高后降低;当退火温度为750℃时,在预应变量为6%的前提下可实现5.3%的可回复应变。其组织结构观察结果表明,经冷轧、退火处理后,合金中α"马氏体形貌由“V”字型自协作组态向择优取向的单一取向马氏体板条转化,界面可动性提升,马氏体临界再取向应力降低,形状记忆性能提高。     

热处理对Ti-50.8Ni合金相变行为和拉伸性能的影响

采用Pyis Dyiamond差热分析仪和电子万能试验机,研究了固溶、固溶加时效对Ti-50.8Ni合金的相变行为和拉伸性能的影响。结果表明:热处理制度对Ti-50.8Ni合金的相变温度和相变行为有明显影响,Ti-50.8Ni合金在时效过程中产生析出相,导致相变温度和相变行为发生改变,进而对室温拉伸性能产生影响。     

热处理对GH783合金组织与性能的影响

研究了抗氧化型低膨胀高温合金GH783的热处理制度.结果表明:随着固溶温度的升高,晶粒有所长大,在1140℃固溶晶粒开始不均匀长大;室温拉伸强度有所下降,高温拉伸塑性有所升高,持久塑性在1115℃固溶时最高.随着β时效温度的升高,二次β相明显增多,γ′相也发生比较明显的变化;在845℃进行β时效,合金可以获得良好的组织和综合性能.     

双重退火对ZTC18铸造钛合金组织及性能的影响

目的 研究ZTC18合金双重退火热处理时合金微观组织和力学性能的变化规律。方法 通过对ZTC18合金熔模精密铸造拉伸试棒试验件进行双重退火热处理实验,对比不同热处理工艺铸件的微观组织和力学性能,分析其变化规律。结果 不同的双重退火温度下,晶粒尺寸无明显变化,随着第2级退火温度升高,晶粒内部初生α相由长针状逐渐变化为棒状及等轴颗粒,次生α相逐渐减少,合金的强度随第2级退火温度升高而降低,塑性则呈增加趋势。结论 通过双重热处理可以达到调整合金强度塑性比的目的,对比HIP后的室温拉伸数据,在二级退火温度为610和590 ℃的试样（空冷或炉冷）的强度和塑性综合匹配性较好,抗拉强度能够达到1100 MPa,伸长率大于11%。     

热暴露对TiAl合金室温拉伸性能影响的研究进展

室温拉伸塑性是TiAl合金这类低损伤容限材料工程化应用必须考虑的重要指标之一。高温热暴露后TiAl合金的室温塑性显著降低,这不利于TiAl合金部件的应用可靠性。概述了高温热暴露对TiAl合金室温拉伸性能特别是室温拉伸塑性的影响,重点归纳了高温热暴露造成的表面性质变化对该合金室温塑性不利影响的可能机制,并提出了抑制热暴露所致室温塑性降低的可能途径。分析表明,热暴露导致TiAl合金室温拉伸塑性降低,是表面氧化致脆、表面残余应力以及环境潮气等因素综合作用的结果,其中表面氧化致脆是直接原因。改善基体的抗氧化性或者形成可抑制表面裂纹向基体扩展的有利组织,是保持TiAl合金高温使用后室温拉塑性水平的有效途径。     

热暴露对TA19钛合金锻件拉伸性能的影响

分别测试了固溶时效处理TA19钛合金锻件经400℃和500℃热暴露100h后的室温和高温拉伸性能,研究了热暴露对其拉伸性能的影响。结果表明:TA19钛合金锻件经400℃和500℃热暴露100h后,其表面形成的脆化层对合金强度影响不大,合金没有产生热暴露效应,表明TA19钛合金的热暴露效应起始温度大于500℃。     

显微组织对TA15合金高温拉伸性能的影响

研究了显微组织变化对TA15合金500℃高温拉伸性能的影响。结果表明:初生α相含量增加、α相方向性增强、次生α片变厚及β晶粒尺寸变粗大等显微组织的变化,可使TA15合金500℃高温抗拉强度降低,最大降幅达90MPa以上。研究表明,随初生α相含量增加,增多了晶界数量,而随温度升高晶界强度比晶粒强度下降快,导致高温抗拉强度随初生α相含量增加而降低。     

Effect of rolling temperature on microstructure and mechanical properties of 6063 Al alloy

Aluminium alloy (6063) was severely rolled upto 92% thickness reduction at liquid nitrogen temperature and room temperature to study the effect of rolling temperature on its mechanical properties and microstructural characteristics by using tensile tests and SEM/electron back scattered diffraction (EBSD), transmission electron microscope (TEM), DSC, X-ray diffraction (XRD) as compared to room temperature rolled (RTR) material with the same deformation strain. An improved strength (257 MPa) of cryorolled 6063 Al alloy was observed as compared to the room temperature rolled alloy (232 MPa). The improved strength of cryorolled alloy is due to the accumulation of higher dislocation density than the room temperature rolled material. The tensile properties of cryorolled alloy and the alloy subjected to different annealing treatments were measured. The cryorolled alloy subjected to annealing treatment at 300 °C for 5 min exhibits an ultrafine-grained (UFG) microstructure with improved tensile strength and ductility.     

固溶温度对TA19钛合金组织及性能的影响

采用5种不同固溶温度和相同时效温度的热处理制度对TA19钛合金进行固溶时效处理,研究不同固溶温度对显微组织和力学性能的影响。结果表明,固溶温度对TA19钛合金显微组织的初生α相含量影响显著;经相变点以下10℃到50℃固溶保温1 h后风冷,再经595℃时效保温8 h后空冷,获得的室温和高温力学性能均能满足AMS 4975标准的要求;固溶温度选择相变点以下10℃时,TA19钛合金的室温和高温力学性能及蠕变性能匹配最好,对应的显微组织中初生α相含量为15%~18%。     

TA22合金扩散焊接接头的组织与性能

利用真空扩散焊接方法，研究不同焊接温度对TA22合金接头组织和性能的影响，并通过焊后热处理改善接头的综合性能。结果表明:随着扩散焊接温度的升高，TA22合金扩散焊接接头的抗拉强度和屈服强度逐渐降低，而伸长率和断面收缩率则表现出先升高后降低的趋势，其拐点在950℃。经850℃退火处理后，TA22合金扩散焊接接头的塑性得到明显的改善。      

Mechanical behavior of nanocrystalline TiNi alloy produced by severe plastic deformation

Nanocrystalline (NC) Ti₄₉₄Ni_50:6 alloy with a different mean grain size in a range of 20–100 nm has been successfully produced using severe plastic deformation by high pressure torsion and further annealing at various temperatures. The features of microstructure and martensitic transformation of the NC TiNi have been studied. During tensile tests the effects of the grain size on mechanical properties at room and elevated temperatures are studied and discussed. The NC TiNi exhibits an unusual increased strength but low ductility at room temperature. However, it demonstrates enhanced strength and ductility at higher temperatures.     

激光熔化沉积(TiB+TiC)/TA15原位钛基复合材料的显微组织与力学性能

利用激光熔化沉积工艺制备了TiB+TiC增强相体积分数分别为9%、11%、22%及57%的4种(TiB+TiC)/TA15原位钛基复合材料。随增强相含量提高,TiB形态由片层状向棱柱状转化,TiC形态由不规则颗粒状向枝晶状转化,钛基复合材料硬度及弹性模量均显著提高而塑性明显下降。增强相体积分数约为9%的复合材料表现出较好的综合力学性能,增强相体积分数大于11%后复合材料的抗拉强度急剧降低。与激光熔化沉积态TA15钛合金相比,TiB+TiC增强相体积分数约为9%的复合材料抗拉强度（1040 MPa）及屈服强度（935 MPa）均提高约12%。      

Structural Applications of NiAl

Alloys based on NiAl offer significant payoffs as structural materials in gas turbine applications due to a unique range of physical and mechanical properties These properties include high melting temperature. low density. high thermal conductivity. and excellent environmental resistance Very significant improvements in the strength and ductility of NiAl single crystals have been achieved through alloying. Tensile strength and stress rupture properties which compete with current Ni-base Superalloys have been achieved through precipitation of an ordered L21 Heusler phase in NiAl single crystals Room temperature tensile ductility as high as 6% has been produced in NiAl single crystals containing less than 0.5% (atomic) of Fe. Ga or Mo. However. a single alloy with both room temperature ductility and sufficient high temperature strength has not yet been developed. While activity to develop on alloy with both high temperature strength and room temperature ductility continues. the Current approach also emphasizes design and test methodologies which can accept a material with limited ductility and damage tolerance More work is required on measuring and understanding strain rate sensitivity and impact behaviour While several significant challenges still remain. excellent progress has been made in many areas, and the prognosis for using NiAl alloys as high temperature structural materials is promising     

Effect of initial orientation on the microstructure and mechanical properties of textured AZ31 Mg alloy during torsion and annealing

We studied the effect of crystallographic orientation and temperature on the microstructure and mechanical properties of extruded AZ31 magnesium alloy bar by torsion and subsequent annealing. The results show that the orientation between torsion axis (TA) and extrusion direction (ED) has a significant impact on the microstructure evolution. With TA parallel to ED, profuse extension twins appeared. After annealing, zones close to the surface were completely recrystallized and refined, while the center still had some extension twins left. With TA perpendicular to ED, extension twins were inhibited. It is speculated that, except extension twins, contraction twins is also acting as a major deformation mode. Upon annealing, this specimen was completely recrystallized, even at the center, which is considered as a result of more preferred nucleation sites for static recrystallization from contraction twins. As demonstrated, the temperature has little impact on the microstructure development when twisted at room temperature or liquid nitrogen temperature. Moreover, the compression tests show that the compression ductility and yield strength were improved simultaneously for both samples when compressed on the direction either along ED or perpendicular to ED, due to the combined effects of grain refinement and texture weakening.     

Synergy effect of multi-strengthening mechanisms in FeMnCoCrN HEA at cryogenic temperature

High-entropy alloys(HEAs)have attracted great research interest owing to their good combination of high strength and ductility at both room and cryogenic temperatures.However,expensive raw mate-rials are always added to overcome the strength-ductility trade-off at low temperatures,leading to an increased production cost for the cryogenically used alloys.In this work,a series of nitrogen-doped FeMnCoCr HEAs have been processed by homogenization annealing,cold rolling and recrystallization annealing followed by water quenching.The microstructural evolution and mechanical properties of the alloys are studied systematically.The Fe49Mn30Co10Cr10N1 alloy shows excellent mechanical properties at both 293 K and 77 K.Particularly,the yield and ultimate tensile strength of 1078 and 1630 MPa are achieved at the cryogenic temperature,respectively,while a satisfactory uniform elongation of 33.5％is maintained.The ultrahigh yield strength results from the microstructure refinement caused by the acti-vation of athermal martensitic transformation and mechanical twinning that occur in the elastic regime together with the increased lattice friction due to the cryogenic environment.In the plastic regime,the dynamic Hall-Petch effect caused by twinning,martensitic transformation,and reverse transformation together with the high barrier to dislocation motion jointly contribute to the ultrahigh tensile strength.Simultaneously,the transformation induced plasticity(TRIP)and the twinning induced plasticity(TWIP)effects jointly contribute to the ductility.The design strategy for attaining superior mechanical properties at low temperatures,i.e.by adjusting stacking fault energy in the interstitial metastable HEAs,guides the development of high-performance and low-cost alloys for cryogenic applications.