Effect of thermomechanical treatment on microstructure and properties of Cu-Cr-Zr-Ag alloy

The effects of thermomechanical treatment on the properties and microstructure of Cu-Cr-Zr alloy and Cu-Cr-Zr-Ag alloy were investigated. Ag addition improves the mechanical properties of the alloy through solid solution strengthening and brings a little effect on the electrical conductivity of the alloy. A new Cu-Cr-Zr-Ag alloy was developed, which has an excellent combination of the tensile strength, elongation, and electrical conductivity reaching 476.09 MPa, 15.43% and 88.68% IACS respectively when subjected to the optimum thermomechanical treatment, i.e., solution-treating at 920℃ for 1 h, cold drawing to 96% deformation, followed by aging at 400℃ for 3 h. TEM analysis revealed two kinds of finely dispersed precipitates of Cr and CuaZr. It is very important to use the mechanisms of solid solution strengthening, work hardening effect as well as precipitate pinning effect of dislocations to improve tensile strength of the alloy without adversely affecting its electrical conductivity.

Effects of Thermomechanical Treatment on the Mechanical Properties and Microstructures of 6013 Alloy

The mechanical properties and microstructures of 6013 alloy after different thermomechanical treatments were investigated. The detailed dislocation configurations after deformation and morphologies of age hardening precipitates were examined through transmission electron microscopy （TEM）. The experimental results show that the thermomechanical treatment can significantly enhance the strength of 6013 alloy, and has a similar influence trend on single and two-step aging behaviors. With the increasing deformation ratio, the peak-hardness （HVmax） increases, the time to HV shortens, and the density of tangled dislocation network increases. The aging precipitates become larger and inhomogeneous by applying thernomechanical treatment.

Effect of thermomechanical treatment on microstructure and hardness behavior of AZ63 magnesium alloy

Due to their high specific strength and low density, magnesium alloys are widely used in many weight-saving applications. This research is aimed at investigating the microstructure and hardness of commercial AZ63 alloy specimens subjected to two different thermomechanical treatments （TMTs）. For the first TMT, after solution treated at the temperature of 380 ℃ for 20 h, AZ63 alloy specimens were 5% cold worked by rolling process followed by ageing at the temperatures of 150 ℃and 250 ℃ for 3, 9 and 25 h. In the second TMT, the specimens were solution treated at the temperature of 380 ℃ for 20 h, underwent 2% cold worked and quenched in water of 0 ℃. Half of the specimens were then 2% cold worked whilst the rest were rolled to 8% cold worked. All the specimens were then aged at the temperatures of 150 ℃ and 250 ℃ for 3, 9 and 25 h. Optical microscope was used to analyze the microstructures of the specimens. Hardness test was too conducted to measure the effect of the treatments on the specimens. Results show that two-step aging enhances the hardness of the specimens due to the distribution of fine β-phase （MglTA112） in the alloy matrix. The results also reveal that, the best hardness from the first TMT was produced by specimen that was pre-aged at 150 ℃ whereas, in the second TMT, aging at 250 ℃ exhibited the best hardness values.

Effect of thermomechanical cyclic quenching and tempering treatments on microstructure,mechanical and electrochemical properties of AISI 1345 steel

Thermomechanical cyclic quenching and tempering(TMCT)can strengthen steels through a grain size reduction mechanism.The effect of TMCT on microstructure,mechanical,and electrochemical properties of AISI 1345 steel was investigated.Steel samples heated to 1050℃,rolled,quenched to room temperature,and subjected to various cyclic quenching and tempering heat treatments were named TMCT-1,TMCT-2,and TMCT-3 samples,respectively.Microstructure analysis revealed that microstructures of all the treated samples contained packets and blocks of well-refined lath-shaped martensite and retained austenite phases with varying grain sizes(2.8–7.9μm).Among all the tested samples,TMCT-3 sample offered an optimum combination of properties by showing an improvement of 40%in tensile strength and reduced 34%elongation compared with the non-treated sample.Nanoindentation results were in good agreement with mechanical tests as the TMCT-3 sample exhibited a 51%improvement in indentation hardness with almost identical reduced elastic modulus compared with the non-treated sample.The electrochemical properties were analyzed in 0.1 M NaHCO_(3) solution by potentiodynamic polarization and electrochemical impedance spectroscopy.As a result of TMCT,the minimum corrosion rate was 0.272 mm/a,which was twenty times less than that of the nontreated sample.The impedance results showed the barrier film mechanism,which was confirmed by the polarization results as the current density decreased.

Low cycle fatigue improvement of powder metallurgy titanium alloy through thermomechanical treatment

A low-cost β type Ti-1.5Fe-6.8Mo-4.8Al-1.2Nd (mass fraction, %)(T12LCC) alloy was produced by blended elemental powder metallurgy(P/M) method and subsequent thermomechanical treatment. Low cycle fatigue(LCF) behavior of P/M T12LCC alloy before and after thermomechanical treatment was studied. The results show that the LCF resistance of P/M titanium alloy is significantly enhanced through the thermomechanical treatment. The mechanisms for the improvement of LCF behavior are attributed to the elimination of residual pores, the microstructure refining and homogenization.

Thermomechanical treatment of super high strength Cu-8.0Ni-1.8Si alloy

The microstructures and properties of Cu-8.0Ni-1.8Si alloy subjected to different heat treatments were examined by mechanical and electrical properties measurements,optical and transmission electron microscopes observation. The results show that the precipitation process during aging can be accelerated by the cold deforming before aging. As the Cu-8.0Ni-1.8Si alloy is subjected to solution treatment at 970 ℃ for 4 h,cold rolling to 60% reduction,and then aging at 450 ℃ for 60 min,its properties are σb=1 050 MPa,σ0.2=786 MPa,δ=3.2% and conductivity 27.9%(IACS). The strengthening mechanisms of the alloy include spinodal decomposition strengthening,ordering strengthening and precipitation strengthening. The precipitation of the alloy is nano-scale Ni2Si phase.

Thermomechanical treatment of austempered ductile iron

The production of lightweight ferrous castings with increased strength properties became unavoidable facing the serious challenge of lighter aluminum and magnesium castings.The relatively new ferrous casting alloy ADI offers promising strength prospects,and the thermo-mechanical treatment of ductile iron may suggest a new route for production of thin-wall products.This work aims at studying the influence of thermomechanical treatment,either by ausforming just after quenching and before the onset of austempering reaction or by cold rolling after austempering.In the first part of this work,ausforming of ADI up to 25% reduction in height during a rolling operation was found to add a mechanical processing component compared to the conventional ADI heat treatment,thus increasing the rate of ausferrite formation and leading to a much finer and more homogeneous ausferrite product.The kinetics of ausferrite formation was studied using both metallographic as well as XRD-techniques.The effect of ausforming on the strength was quite dramatic(up to 70% and 50% increase in the yield and ultimate strength respectively).A mechanism involving both a refined microstructural scale and an elevated dislocation density was suggested.Nickel is added to ADI to increase hardenability of thick section castings,while ausforming to higher degrees of deformation is necessary to alleviate the deleterious effect of alloy segregation on ductility.In the second part of this work,the influence of cold rolling(CR)on the mechanical properties and structural characteristics of ADI was investigated.The variation in properties was related to the amount of retained austenite(γr)and its mechanically induced transformation.In the course of tensile deformation of ADI,transformation induced plasticity(TRIP)takes place,indicated by the increase of the instantaneous value of strain-hardening exponent with tensile strain.The amount of retained austenite was found to decrease due to partial transformation of γr to martensite under the CR strain.Such strain-induced transformation resulted in higher amounts of mechanically generated martensite.The strength and hardness properties were therefore increased,while ductility and impact toughness decreased with increasing CR reduction.

Thermomechanical effect on magnetic behaviors of antiferromagnetic Mn-Fe(Cu) alloy

The effect of thermomechanical treatment on the magnetic properties of Mn85.5Fe9.0Cu0.5 alloy was studied by use of a materials testing machine, a vibrating sample magnetometer, an X-ray diffractometer, a homogeneously and adjustably magnetic field and strain gauges. The results show that the orientation of fct phase and magnetic domains is affected by the thermomechanical treatment. When the compressive strain of thermomechanical treatment is -1.2%, the magnetic-field-induced strain reaches the highest value in the adapted situation.

形变热处理对Ti-Nb-Zr合金组织及超弹性行为的影响

Ti-Nb-Zr合金具有低弹性模量、高强度以及优异的生物相容性,在生物医用材料领域备受关注。Ti-Nb-Zr合金的超弹性归因于β↔α″相变。综述了Ti-Nb-Zr合金的弹性模量和超弹性的影响因素及变化规律。通过添加合金元素来调整相变温度和滑移临界应力,应力诱发马氏体相变更易发生,β相塑性变形延迟出现,获得更大的相变应变和恢复应变。总结了Ti-Nb-Zr合金的形变热处理与超弹性效应之间的关系和作用机制。冷轧后短时间热处理可以增加位错滑移的临界应力、避免其他相(ω或α相)的生长,保持β相的稳定性、提高合金的恢复应变和超弹性。

球磨处理对小米-小麦粉混合面团流变学及热机械学特性的影响

以小米为原料通过球磨处理制备球磨小米粉,再将小米粉与小麦粉按照一定比例混合制备混合面团,研究不同球磨处理对混合面团流变学及热机械学特性的影响。结果表明:在球磨时间4.0 h、球磨转速450 r/min、球料质量比3∶1时,混合面团的流变学特性最佳且热机械学特性较佳,说明适当的球磨处理可以改善小米-小麦粉混合面团的流变学和热机械学特性。

形变热处理工艺(TMTP)对T91钢显微组织的影响

在Gleeble 1500热模拟实验机上采用热压缩实验方法,研究了形变热处理工艺即在奥氏体未再结晶区变形后直接淬火对T91铁素体耐热钢微观组织的影响。结果表明:形变热处理工艺明显优化了T91钢的组织结构,使T91钢的马氏体板条趋于细化,并且能生成更多纳米级碳氮化物颗粒来进一步进行组织强化,从而论述了采用形变热处理工艺来提高铁素体耐热钢耐热温度的可行性。

热机械处理Al-Co-Fe-Ni共晶高熵合金组织性能研究

共晶高熵合金具有优异的强塑性匹配,同时还兼具传统共晶合金良好的铸造性能,对高熵合金的实际化应用有着重大的意义。而如何进一步提升共晶高熵合金的强塑性能,成为了高熵合金领域的研究热点。本文以Al-(21)Co_(19.5)Fe_(9.5)Ni_(50)共晶高熵合金为研究对象,探究了热机械处理对合金微观组织和拉伸力学性能的影响规律。并结合合金微观组织和相结构对合金应变硬化能力的影响,阐明了热机械处理条件下合金的变形机制及其对合金力学性能的影响。结果表明,经过热机械处理后合金由共晶层片组织转变为近完全等轴晶组织,且FCC相中析出L1_(2)相。热机械处理后合金在拉伸变形过程中,随着应变量的增加FCC相内位错密度增加,B2相发生应力诱发马氏体相变而形成具有相互交错孪晶结构的L1_(0)相,最终在FCC相与B2相双重强化机制下,表现出更高的屈服强度(551 MPa)和断裂伸长率(10.2%),加工硬化率曲线出现显著变化。

共晶高熵合金研究进展

共晶高熵合金是凝固过程中发生共晶转变的多组元合金,具有优异的液态充型能力和机械性能,适用于生产形状复杂、对力学性能要求较高且不能进行热机械处理的零件。共晶高熵合金具有4种及以上元素,且相组成和组织形貌对合金成分变化不敏感,因此具有很大的性能调控空间及工艺窗口。通过调控共晶高熵合金的相组成及组织形貌可使其叠加各种优异性能。本文从设计方法、制备工艺、组织结构、力学及理化性能等方面综述了共晶高熵合金的研究现状,并对共晶高熵合金未来的发展进行展望。

热处理对超低碳CrMnN奥氏体不锈钢焊接接头性能的影响

采用等离子弧焊接对QN1804L(下称18Cr)超低碳CrMnN奥氏体不锈钢进行焊接,并对焊接接头分别进行形变热处理和固溶处理。结果表明:焊态下接头组织由奥氏体和铁素体组成,铁素体呈骨架和板条状分布在奥氏体组织中间,焊缝硬度略高于母材的;形变热处理后焊缝组织发生扭曲,晶粒被拉长,焊缝硬度远高于母材的;同时由于形变强化,焊缝强度也明显提高。固溶处理后焊缝中的铁素体在高温转变为奥氏体,未及时转变的呈点状分布,焊缝硬度与母材的基本保持一致;不同热处理后的焊缝均具有较好的耐腐蚀性能。

低硫非调质钢水口结瘤机理解析

非调质钢含有较高的铝,经钙处理工艺后,易导致水口结瘤。采用X射线衍射仪、扫描电子显微镜分析了某厂低硫非调质钢连铸水口结瘤物试样,结合热力学计算分析,揭示水口结瘤的原因。研究表明:水口结瘤物主要为CaS,其在钢液凝固过程中从钢液中以直接、间接两种方式析出,钙添加过量是导致水口结瘤的主要原因,后续可通过优化钢液的钙铝比来保证连铸的顺行,消除结瘤现象。

Influence of Thermomecaniques Treatments on the Proprietes of Al-5.8%Zn-2.7%Mg Alloy

The aim of this work is the demonstration of the effect of thermomechanical treatments on the properties of the alloy Al-5.8%Zn-2.7%Mg by thermal analysis techniques and calorimetry, which are methods of test widely used for research purposes and quality control. The effects of thermomechanical treatments on the two variables namely the coefficient of thermal expansion and heat capacity, we can provide further information for better understanding of the phenomena responsible for the thermodynamic behavior of the alloy. The results showed the one hand, there is great similarity between the linear coefficient of thermal expansion and heat capacity, and secondly the effect of plastic deformation is evidenced by changes in the shape of the curves from the rough. Similarly the kinetics of precipitation of η phase is accelerated in the case of samples homogenized and homogenized + distorted and accompanied by a shift in the temperature range to lower temperatures than those recorded in the case of the material state Gross.

Thermo-Mechanical Treatment on Microstructure and Mechanical Properties of Mg-5.0Sn-1.0Mn-0.4Zr Alloy

The mechanical properties and microstructure of an as-cast Mg-5.0Sn-1.0Mn-0.4Zr alloy were investigated during thermo mechanical treatments consisting of hot extrusion, rolling, and ageing at 200°C. The results indicate that only Mg2Sn phases formed in the Mg matrix, Mn and Zr do not cause the formation of any new phases. The average grain size, tensile strength and elongation were 22 μm, 285 MPa, and 14.5%, respectively, after extrusion + rolling + ageing treatment (ERA). The mechanical properties of ERA alloys with a peak hardness of 81 HV and 6.7% are improved compared with those of EA (extrusion + ageing treatment) samples;these changes are attributed to grain refinement and solid solution strengthening, age hardening, and precipitation strengthening.

Microstructure and mechanical properties of an Mg-4.0Sm-1.0Ca alloy during thermomechanical treatment

The microstructure and mechanical properties of an as-cast Mg-4.0Sm-1.0Ca alloy were investigated during thermome-chanical treatments consisting of hot extrusion, rolling, and aging at 473 K. Mg41Sm5 phases containing Ca and needle-like Mg2Ca phases formed in the Mg matrix, and the average grain size and elongation were 4.2μm and 27%, respectively, after hot extrusion, which implied an increase in ductility. In addition, after the rolling, the grain size was further refined, and the tensile strength in-creased to 293 MPa. A new precipitate Mg3Sm was found in the peak-aged Mg-4.0Sm-1.0Ca alloy and this alloy displayed the best mechanical properties, with a peak hardness of 83 HV and ultimate tensile strength of 313 MPa; these properties were attributed to grain refinement strengthening, solid solution strengthening, work hardening, and precipitation strengthening.

Effect of Thermomechanical Treatment Temperature on Structure and Properties of CFB/M Ultra-High Strength Steel

Modified CCT diagram of carbide-flee bainite-martensite （CFB/M） ultra-high strength steel was established by applying controlled cooling of small samples. In addition, the influence of thermomechanical treatment tem- perature on the structure and properties was discussed. The experimental results showed that when deformed at 860℃ and below, ferrite transformation occurred due to strain. With the decrease of ausforming temperature, the quantity of ferrite increased and strength and toughness were deteriorated. Therefore, certain information was provided for optimizing technical parameter of ausforming process., firstly, the thermomechanical treatment temperature should not be lower than 860 ℃ in order to avoid ferrite formation induced by deformation; secondly, rapid cooling rate is also significant after deformation in order to avoid ferrite precipitation during subsequent cooling stage.