热处理工艺对AFA耐热钢组织和力学性能的影响

为考察热处理工艺对AFA耐热钢组织和力学性能的影响,本文利用光学显微镜、扫描电镜、X射线衍射等技术,研究了新型含铝奥氏体耐热钢(AFA)在不同保温温度和冷却方式下的组织演变规律及力学性能的变化.结果表明:加热温度和冷却方式对试样的显微组织均产生影响.随着保温温度的升高,晶粒的平均尺寸逐渐增大.在1 150和1 200℃...     

贝氏体区等温时间对TRIP钢残奥及力学性能影响

为研究贝氏体区等温时间对热轧TRIP钢残余奥氏体和力学性能的影响,采用金相显微镜、X射线衍射、拉伸实验等方法对3种不同贝氏体区等温时间下制备的热轧TRIP钢进行分析.结果表明:随着贝氏体等温时间的延长,残余奥氏体量减少而残余奥氏体碳含量增加,残余奥氏体晶粒尺寸及残余奥氏体形貌变化不大;热轧TRIP钢的力学性能随着贝氏体...     

Effect of microstructure morphology on mechanical properties of quenching and partitioning steel

In order to illuminate the relationship between microstructure morphology and final properties of the quenching and partitioning(Q&P) steel, the samples with different microstructure morphology (equiaxed and lamellar) and same volume fraction of each phase are obtained by controlling the initial microstructure and Q&P heat treatment. Because of the feature of microstructure morphology, a large yield ratio and total elongation are obtained in the lamellar sample though yield strength and ultimate tensile strength are relatively lower than that of equiaxed sample. Moreover, the lamellar sample produces a continuous work-hardening rate and better the fracture toughness compared to the equiaxed sample. Thus the lamellar sample is more suitable to be used as automotive structural components.     

形变热处理对T91钢组织和性能的影响

用热模拟机模拟T91铁素体耐热钢的形变热处理工艺,在T91钢的奥氏体未再结晶区(650-850℃)对其进行不同程度的变形,研究了直接淬火对T91钢的组织形成和力学性能的影响.结果表明:与传统热处理相比,形变热处理不仅使T91钢的组织明显细化,而且生成更多的MX型纳米级碳氮化物颗粒.通过拉伸实验表明:形变热处理工艺可以明显提高T91钢的强度,进而达到提高其使用温度的目的.     

Effect of rolling deformation and solution treatment on microstructure and mechanical properties of a cast duplex stainless steel

The present study deals with the effect of rolling deformation and solution treatment on the microstructure and mechanical properties of a cast duplex stainless steel. Cast steel reveals acicular/Widmanst?tten morphology as well as island of austenite within the $\boldsymbol\delta $ -ferrite matrix. Hot rolled samples exhibit the presence of lower volume percent of elongated band of $\boldsymbol\delta $ -ferrite ( $\boldsymbol\sim $ 40%) and austenite phase which convert into finer and fragmented microstructural constituents after 30% cold deformation. By the solution treatment, the elongated and broken crystalline grains recrystallize which leads to the formation of finer grains (<10? $\boldsymbol\mu $ m) of austenite. X-ray diffraction analysis has corroborated well with the above-mentioned microstructural investigation. Enhancement in hardness, yield strength and tensile strength values as well as drop in percent elongation with cold deformation increases its suitability for use in thinner sections. 30% cold rolled and solution treated sample reveals attractive combination of strength and ductility (25·22?GPa%). The examination of fracture surface also substantiates the tensile results. The sub-surface micrographs provide the potential sites for initiation of microvoids.     

Effects of power ultrasonic treatment on microstructure and mechanical properties of T10 steel

The microstructure and mechanical properties of T10 steel treated with power ultrasonic during solidification are investigated. A self-developed experimental setup is built for the propagation of ultrasonic vibration into the melt along the horizontal direction. Experimental results indicate that the power ultrasonic applied in the melt can not only refine the microstructure remarkably but also enhance both tensile strength and ductility values of T10 steel. Furthermore, the finer grains can be obtained due to the higher incident ultrasonic power. SEM fractographs show that the sample with 600 W ultrasonic treatment exhibits a ductile fracture surface covered with deformation dimples, while the sample without ultrasonic treatment shows a brittle fracture surface. The effects of power ultrasonic on the melt are discussed.     

Influence of austempering temperature on the mechanical properties of a low carbon low alloy steel

In this investigation, a new low alloy and low carbon steel with exceptionally high strength and high fracture toughness has been developed. The effect of austempering temperature on the microstructure and mechanical properties of this new steel was examined. The influence of the microstructure on the mechanical properties and the fracture toughness of this steel was also studied.Test results show that the austempering produces a unique microstructure consisting of bainitic ferrite and austenite in this steel. There were significant improvement in mechanical properties and fracture toughness as a result of austempering heat treatments. The mechanical properties as well as the fracture toughness were found to decrease as the austempering temperature increases. On the other hand, the strain hardening rate of steel increases at higher austempering temperature. A linear relationship was observed between strain hardening exponent and the austenitic carbon content.     

轧制工艺对D6A钢微观组织和力学性能的影响

为了研究轧制工艺对D6A钢组织及力学性能的影响,分别制备了87％和93％压下量的D6A钢,并通过EBSD和拉伸性能测试进行了分析.结果表明,随轧制压下量由87％增加至93％,D6A钢中晶粒尺寸显著减小,由5 μm减至1 μm,小角度晶界含量则大幅增加,由55％增至80％.随轧制压下量的增加,D6A钢的抗拉强度及屈服强度...     

应变速率对热冲压淬火-配分钢显微组织与力学性能的影响EI北大核心CSCD

采用分离式Hopkinson压杆对热冲压淬火-配分(HS-Q&P)钢在0~12000 s^(-1)应变速率范围内进行动态压缩实验,利用SEM,EBSD,XRD等分析表征手段探究动态压缩过程中试样的变形行为。结果表明:实验钢在不同速率下的变形行为基本相似且分为3个阶段,在平台处应力有小幅度增加,增幅更多体现在应变上。在压缩过程中出现的绝热升温会带来软化效应。残余奥氏体的存在会提高实验钢的强度和塑性变形能力。钢中残余奥氏体发生相变诱导塑性(transformation induced plasticity,TRIP)效应减少的体积分数与马氏体增加的体积分数基本一致,证明TRIP效应为钢中主要的强化机制。同时,通过SEM可观测到残余奥氏体发生TRIP效应转变成细小针状马氏体,随着应变速率增加,晶格畸变越来越严重,EBSD图像中可以观测到部分形变孪晶,在不同应变速率下,〈001〉取向的晶粒都会更容易产生形变孪晶。     

Effect of pre-quenching on martensite-bainitic microstructure and mechanical properties of GCr15 bearing steel

In order to improve the strength and toughness of steel GCr15 (52100), the effect of different amounts of pre-transformed martensite on the kinetics of isothermal bainitic transformation and the strength and toughness of martensite-bainitic (MB) duplex microstructure has been studied by using pre-quenching after conventional 850°C heating to different temperatures (220, 200, 180°C) below M _s and then isothermal treatment at 240°C. The experimental results show that the accelerating effect of pre-quenched martensite on isothermal bainitic transformation principally depends upon the pre-quenching temperature (the amount of pre-quenched martensite). The MB duplex microstructure with 33% pre-transformed martensite has the optimum combination of strength and toughness.     

Effect of microstructure on mechanical properties in weld-repaired high strength low alloy steel

To understand the effect of microstructure on mechanical properties of weld-repaired high strength low alloy (HSLA), as-received and weld-repaired HSLA with and without buffer layers (BLs) were prepared. Microstructure analysis was carried out using optical microscope and SEM, and mechanical properties were measured by Vickers hardness test and fatigue test.The fatigue resistance of weld-repaired HSLA without BL was deteriorated with comparing to parent metal (PM). Meanwhile, Vickers hardness (VH) showed an obviously reduction in the melted parent metal (MPM), which was due to formation of predominately block ferrite. For the weld-repaired HSLA with BL, the VH and fatigue resistance increased with the incorporation of 4 mm BL, which was mainly due to formation of lath ferrite and fine-grained pearlite and bainite. When BL thickness increased to 10 mm, the VH and fatigue resistance decreased, which was because the thick BL diluted the MPM. VH number from low temperature (below melting point) heat affected zone (HAZ) fluctuated, but had a little scatter. However, the fatigue crack growth rate from HAZ was not obviously affected by the welding as comparison with the PM.     

Effect of drawing strain rate on microstructure and mechanical properties of cold-drawn pearlitic steel wires

Journal of Materials Science - Microstructural evolution of cold-drawn pearlitic steel wires (CPWs) with different drawing strain rates and their effects on mechanical properties of CPWs were...     

回火方式对调质高强度钢组织和性能的影响

为改善高强度钢的塑性和韧性,对同一种低合金高强度钢进行两种不同回火方式的调质处理,淬火+缓慢加热回火的传统调质与淬火+感应加热回火的新调质工艺,分析该工艺对钢的组织与性能的影响.利用扫描电镜和透射电镜观察组织及析出物的变化,采用X射线衍射仪分析了钢中残余奥氏体体积分数.结果表明:两种工艺下,钢的组织均为板条宽300～500 nm左右的马氏体组织,感应加热回火调质工艺处理后,板条组织明显,析出物大多约为20 nm,比传统调质处理后的细小;两种不同热处理工艺均能提高钢的屈服强度.感应加热至500℃回火后试验钢具有16%以上的延伸率,-40℃冲击功达到32 J,优于传统调质工艺处理钢板的综合性能.感应加热回火能获得更多小尺寸析出物和更多的残余奥氏体,有利于改善钢的塑性和韧性.     

双相钢拼焊板温拉伸力学性能及组织分析

为了揭示温变形工艺参数对双相钢拼焊板宏观力学性能及组织演变的影响规律,在不同变形温度和应变速率条件下对DP590双相钢拼焊板进行温拉伸试验和微观组织观察,将变形温度和应变速率对材料温成形过程的综合影响统一为Zener-Hollomon(Z)参数来研究材料宏观力学性能和微观组织演变.实验结果表明,随着Z参数的降低,材料越容易发生动态再结晶,流变应力-应变曲线越低,断后延伸率逐渐提高,平均晶粒尺寸有长大的趋势.本研究对于通过Z参数优化DP590双相钢拼焊板温变形宏观力学性能和微观组织具有一定的参考价值.     

Effect of annealing treatment on the microstructure and mechanical properties of ultrafine-grained aluminum

Microstructural and property evolution of commercial pure Al subjected to multi-axil compression (MAC) and subsequent annealing treatment were investigated. After series of MAC pressings up to 15 passes, the samples were annealed at different temperatures. The deformed and deformed with sequent annealing treatment samples were characterized by X-ray diffraction, electron back scatter diffraction (EBSD), transmission electron microscopy (TEM) and tensile tests. The present results showed that on annealing the grain structures coarsen and transform from lamellar to equiaxed ones. Remarkably, the fraction of high angle grain boundaries drastically increases from 29.3% to 76.3% after annealing at 60 °C. Meanwhile, a significant decrease of lattice microstrain is observed after annealing, from 0.0839% to 0.0731% at 130 °C. A controlled 30 min annealing treatment on ultrafine-grained (UFG) Al at 60 °C can result obviously in a higher strength and a lower elongation, which may be associated with the nucleation and subsequent motion of dislocations in grain boundaries. As the annealing temperature is above 60 °C, the yield strength decreases and elongation increases gradually, which is attributed to the grain coarsening and microstructural enhancement.     

Effect of the heat treatment on the microstructure and mechanical properties of medium-Mn-steels

ABSTRACT

The heat-treatment (HT) schedule and selected annealing parameters have a substantial effect on the microstructure and mechanical properties of medium-Mn-steels. The structure morphology depends on the fact, whether the austenite-reverted transformation takes place from deformed (one-step HT) or non-deformed (two-step HT) microstructures. Depending on the intercritical annealing temperature, the stability of the retained austenite can be altered to a large extent. As a result, the mechanical properties can be adjusted from high strength with excellent ductility to very high strength with reasonable ductility. The present contribution, therefore, elucidates the dependence of the microstructural characteristics and material behaviour on the HT parameters for medium-Mn alloy compositions with different Mn-contents.

This paper is part of a Thematic Issue on Medium Manganese Steels.     

Effect of post weld heat treatment on the microstructure and mechanical properties of ITER-grade 316LN austenitic stainless steel weldments

The effect of postweld heat treatment (PWHT) on the microstructure and mechanical properties of ITER-grade 316LN austenitic stainless steel joints with ER316LMn filler material was investigated. PWHT aging was performed for 1 h at four different temperatures of 600 °C, 760 °C, 870 °C and 920 °C, respectively. The microstructure revealed the sigma phase precipitation occurred in the weld metals heat-treated at the temperature of 870 °C and 920 °C. The PWHT temperatures have the less effect on the tensile strength, and the maximum tensile strength of the joints is about 630 MPa, reaching the 95% of the base metal, whereas the elongation is enhanced with the rise of PWHT temperatures. Meanwhile, the sigma phase precipitation in the weld metals reduces the impact toughness.     

Effect of nickel on microstructure and mechanical properties of heat affected zone of low carbon steel

Abstract

In the present study, the effect of nickel along with varying heat input on the microstructure and mechanical properties of the heat affected zone (HAZ) of a low carbon steel was investigated. Experiments were carried out in which low carbon steel specimens with five different nickel contents, 1, 2, 2.9, 4.1, and 5.2 wt-%, were welded using a submerged arc welding machine with heat inputs of 0.5, 1, and 2 kJ mm^-1. Following welding, the microstructure, hardness, and toughness of the HAZs were determined. From the results, attempts were made to establish a relationship between heat input, nickel content, microstructure, hardness, and toughness. Charpy impact testing and microstructural observation showed that, for a heat input of 0.5 kJ mm^-1, nickel contents between 2.9 and 5.2 wt-% were effective in forming lower transformation products, such as martensite, thereby producing lower toughness values. It was subsequently found that, taking into consideration the microstructure, hardness, and toughness of the HAZ, a lower heat input for a nickel content of 1 wt-% and a medium heat input for nickel contents between 2 and 5.2 wt-% gave good results.     

Mn含量对低碳中锰TRIP钢组织性能的影响

为研究连续退火工艺生产中锰TRIP钢汽车板的可行性,采用CCT-AY-Ⅱ型钢板连续退火机模拟分析了不同锰含量对中锰TRIP钢组织性能的影响规律.采用SEM、TEM和EBSD等微观分析方法观察不同锰含量中锰TRIP的微观组织,利用XRD法测量了残留奥氏体量,实验测量其力学性能.结果表明:试验钢在650℃保温3 min时,随着锰质量分数(4.8%≤w(Mn)≤8%)的增加,屈服强度先增加后降低,抗拉强度持续升高,断后延伸率则基本不变,维持在20%左右,残余奥氏体含量也随着锰含量的增加而增加;当锰质量分数超过6%(含6%)时,真实应力-应变曲线由于动态应变时效而呈锯齿状,且加工硬化指数远大于5Mn钢.试验钢的高塑性由亚稳奥氏体的TRIP效应和超细晶铁素体或马氏体共同提供.