高碳珠光体钢在温变形过程中的组织变化

用SEM、TEM等方法研究了一种原始组织为层片状珠光体的高碳钢在多向温变形(楔横轧)和单向温变形(压缩)条件下试样心部与表层显微组织的演变情况.结果表明,在多向温变形条件下,试样表层可获得铁素体晶粒与渗碳体颗粒尺寸均在0.3 μm以下的超微细(α θ)复相组织,心部渗碳体片虽已碎断并部分球化,但其排布形态与变形珠光体基本保持一致,而单向温变形条件下的情况则恰好相反;变形过程中试样所受应力、应变状态的不同是引起组织差异的根本原因.     

Influence of Lamellar Direction in Pearlitic Steel Wire on Mechanical Properties and Microstructure Evolution

During cold drawing of pearlitic steel wire,the lamellar structure becomes gradually aligned with the draw-ing axis,which contributes to the ultra-high strength.A direct simulation about the mechanical behaviors and micro-structural evolution of pearlitic lamellae was presented.A representative volume element (RVE)containing one pearlitic colony was established based on the real transmission electron microscope (TEM)observation.The deform-ation of pearlitic colony during tension,shear and wire drawing were successfully simulated.The numerical results show that this metallographic texture leads to a strong anisotropy.The colony has higher yielding stress when the la-mellar direction is parallel and perpendicular to the tensile direction.The lamellar evolution is strongly dependent on the initial direction and deformation mode.The formation of typical period shear bands is analyzed.In the wire draw-ing,the pearlitic colony at the sub-surface experiences a complex strain path:rotation,stretching along the die sur-face,and rotation back.     

Fracture Characteristics of Fully Pearlitic Steel Wire in Tension and Torsion

The fracture characteristics of fully pearlitic steel wires with fine and randomly oriented lamellae have been investigated after tension and torsion,respectively.It is found that the predominant fracture mode under small predeformation is dimple.The analysis of the colony size and the lamellar structure near the fracture surface indicates that each dimple roots from one colony.A simulation of tensile deformation with several pearlitic colonies based on the real scanning electron microscopy(SEM)observation shows that the plastic deformation concentrates and the stress traxiality is larger at the boundaries of colonies.It demonstrates the microcracks initialize at colony boundaries.Thus,the colony size is a significant factor for fracture behaviors under small pre-deformation.On the other hand,the fracture surface is investigated after large pre-deformation via torsion.The results show that fracture characteristics vary with radius from dimples,elongated dimples to the fibrous structure.It indicates that the fracture characteristics are dependent on the pre-deformation.The fracture mode under large pre-deformation becomes an anisotropic fibrous structure instead of dimples.     

超细晶钢在不同温度下塑性变形机制的研究

将晶粒尺寸分别为2、7、80μm的微合金钢在295～973K温度范围内进行单轴拉伸试验，通过对比分析3种不同晶粒尺寸微合金钢的工程应力一应变曲线及微观组织，讨论了超细晶粒钢在不同温度下的塑性变形机制。在295～473K范围内，3种不同晶粒尺寸微合金钢的塑性变形机制以位错运动为主；在573K，晶界滑动开始在超细晶粒钢中出现，在973K，成为塑性变形的主导机制；粗晶粒钢在573～973K范围内以位错运动为塑性变形的主要机制。     

结构钢的形变位错结构和强度

 介绍了各种合金结构钢(铁素体钢、铁素体 珠光体钢和淬火回火钢)的形变位错结构及循环形变位错结构的研究情况,阐述了沉淀硬化合金强化过程的位错缠结机制、静载和动载竞争机制以及循环微裂纹的萌生机制。     

Evolution of the Defect Structure of Pearlitic Steel in Cold Deformation

A method of microdiffraction analysis is developed in order to determine the defect structure of pearlitic steels during cold plastic deformation. The total reduction in the drawing of C86D steel coil is shown to affect the azimuthal blurring of the subreflexes in the microdiffraction pattern and the distortion of the plates in the pearlite colony.     

无取向电工钢的高温塑性变形流动应力

 以指导无取向电工钢热轧工艺为目的,采用Gleeble 1500热模拟试验机进行高温等温压缩,在应变速率为0.01~10s-1和变形温度500~1200℃条件下,对试样进行试验研究。结果表明：随着变形温度的升高,在回复与再结晶过程中发生α-Fe向γ-Fe相的?洌贾挛忍鞅溆αΤ氏帧耙斐！北浠２捎肁rrhenius关系模型,模型参数能很好的与试验结果相吻合。利用模型分别计算得500~800℃时,应力水平因子α=0.0390MPa-1,应力指数n=7.93,结构因子A=1.9×1018 s-1,热变形激活能Q=334.8kJ/mol;1050~1200℃时,应力水平因子α=0.1258MPa-1,应力指数n=5.29,结构因子A=1.0×1028 s-1,热变形激活能Q=769.9kJ/mol。     

陕西省自然科学研究计划项目

 钢和铁基合金通过等径弯曲通道变形(ECAP)可获得超细晶组织，从而改善材料的性能。成功实现了C方式650 ℃时珠光体65Mn钢的等径弯曲通道变形，累积等效真应变约为5。片层状珠光体组织演变成超细的渗碳体颗粒均匀分布于铁素体基体的组织，而且铁素体基体为均匀等轴晶粒，平均晶粒尺寸约为0 3 μm。     

马氏体体积分数对热轧双相钢形变位错结构和断裂的影响

  利用SEM、TEM研究了同一成分的热轧双相钢的马氏体体积分数对形变位错结构和断口组织特征的影响。结果表明,马氏体体积分数为20%～30%时,体积分数增加对双相钢形变位错结构的演变影响较小。且马氏体在变形的后期中将出现伴生的高位错密度区和低位错密度区。断裂时当马氏体体积分数增加到30%,颈缩提前,且微孔有向微裂纹转变的趋势。因此,马氏体体积分数为20%的双相钢的成形性能优于马氏体体积分数为30%的双相钢。     

Microscopic Response of TRIP Steels to Prestrain During Plastic Deformation

In order to uncover the mechanism of elastic modulus degradation during plastic deformation, uniaxial tensile test of transformation-induced plasticity (TRIP) steels under different prestrain levels was carried out. The real elastic modulus unloaded at each prestrain was calculated by linearly fitting. The microstructure evolution with plastic strain and the fracture morphology were monitored by using a scanning electron microscope (SEM). Dislocation density and its distribution were detected under a transmission electron microscope (TEM). Microscopic mechanism of the elastic modulus degradation of TRIP steels was discussed in detail. Experimental results indicated that the investigated TRIP600 steel was of severe elastic modulus degradation during plastic deformation. The new-born martensite distributed among the retained austenite, resulting in the combination of good ductility and high strength for TRIP steels. It was the change of dislocation movement that induced the variation of atomic binding force and finally led to the variation of elastic modulus.     

强变形过程中铁镍合金的微观结构演化机制

 采用透射电镜观察了铁镍(Fe 32%Ni)合金在形变温度500 ℃(＜05Tm)、形变速率10-2 s-1的变形条件下多轴锻造变形过程中的微观结构演变。结果表明,低温多轴锻造强变形可明显细化晶粒,细化过程为：首先,位错墙、位错缠绕等结构通过大量位错滑移运动在原始晶粒内形成;其次,不同方向的变形导致不同方向的滑移系开动,从而致使不同方向的位错墙互相交叉,将原始粗晶粒细分成小尺寸的胞块结构,当变形量达到一定程度时,位错墙和位错缠绕结构内的位错开始重新排列,形成小角度晶界,导致亚晶粒形成;由于变形量不断增加强迫大量的位错在亚晶界处积聚、重排,同时不同方向的变形造成亚晶发生转动,位错重新规则排列及亚晶转动使小角度的亚晶界转变为大角度晶界,从而形成细小的新晶粒。     

金属塑性变形抗力数据库接口软件

编制金属塑性变形抗力数据库时,接口软件具有如下特点:(1)使用系统建立的FOXBASE数据库文件直接作为数据缓冲区;(2)语言系统间接口应用C与FOXBASE的连接,在C系统下操作,可访问任何FOXBASE数据库文件.     

塑料模具钢P20的开发与研制

为开发研制塑料模具钢P20,主要对化学成份设计,P20钢冶炼、轧制、退火工艺和性能进行了研究分析。     

板条马氏体钢变形与断裂过程的原位观察

 在备有拉伸装置的扫描电镜上,原位观察了低碳板条马氏体钢的变形和断裂过程。结果表明,板条马氏体的变形是以滑移方式进行的,位错沿滑移面的滑移受阻,在试样表面留下呈波纹状的变形带。在应力峰值前后,主裂纹开始起裂;在主裂纹扩展过程中,在主裂纹前面的薄弱区域如夹杂等会先起裂形成小裂纹或空洞,随应力加大相邻的微孔聚合、连接长大成新裂纹;在断裂过程中,裂纹在板条束界发生转折。尽管原奥氏体晶粒尺寸小的试样起裂载荷大,不同晶粒尺寸马氏体组织的变形和断裂过程没有本质差别。     

中碳钢形变及冷却过程中的组织演变

热模拟单向压缩下,中碳钢形变温度低于Ad3（786℃）点时,析出形变诱导铁素体（DIF）,DIF量随形变温度降低而提高;在低于750℃形变时,DIF量远高于平衡态铁素体含量54％。DIF析出时碳原子高度富集在铁素体晶界和铁素体／奥氏体界面。形变后在低于A1（719℃）温度等温或控冷过程中。过冷奥氏体将发生不同类型的转变：高于Ad3形变试样中,奥氏体转变为铁素体＋片层状珠光体;低于Ad3点但高于Ar3（645℃）点形变时,未转变奥氏体转变为铁素体＋片层状珠光体＋晶界渗碳体;稍高于Ar3点形变时,将获得铁素体＋弥散渗碳体的球化组织。     

W9Mo3Cr4V钢的超细化处理

采用不同的工艺参数,对Ｗ９Ｍｏ３Ｃｒ４Ｖ钢进行高温变形,获得了一种超细的再结晶组织。进一步分析了产生这种超细组织的原因和条件,为高合金钢的超细化处理提出了一种有效的方法。     

Influence of Plastic Deformation on Thermal Stability of Low Carbon Bainitic Steel

Bainite is metastable due to its high dislocation density,and consequently bainitic steel structures have the problem of thermal stability.Plastic deformation of bainite can further increase dislocation density and change dislocation configuration at the same time.The influence of plastic deformation on thermal stability of low carbon bainitic steel during isothermal holding at 650 ℃ was investigated with hardness analysis,in-situ tracing metallographic analysis and transmission electron microscopy.Bainite in the low carbon steel evolves into polygonal ferrite via recovery and recrystallization during isothermal holding at 650 ℃.There is a considerably long period(about 20h)between end of recovery and commencement of recrystallization of undeformed bainite,in which the hardness of the sample maintains a constant value slightly lower than that before reheating.Slight plastic deformation of bainite induces rearrangement of pre-existing dislocations and forming of low-energy dislocation cells inside bainite laths,which has little influence on thermal stability of bainite,whereas heavy plastic deformation results in obvious dislocation multiplication and accelerates recrystallization of bainite.Recrystallization of heavily-deformed bainite occurs preferentially at prior austenite grains boundaries.The samples subjected to heavy torsion exhibit obviously higher thermal stability than the samples subjected to heavy compression despite their same initial hardness,which can be attributed to different influences of torsion and compression on dislocations and boundaries of bainite.     

镁合金塑性加工新工艺

介绍了镁合金的性能及现状。综述了难变形镁合金的塑性加工新技术,包括氢化处理技术、电塑性加工技术及大塑性变形加工技术。对这几种新加工技术的特点及发展现状进行了详细介绍,最后,总结了这些技术针对镁合金加工的应用前景。     

提高GCr15轴承钢线材预精轧温度的研究

 通过提高GCr15轴承钢φ10mm线材预精轧温度的工业试验,得到了网状碳化物少的细片状珠光体组织,利用实验室热模拟的方法对工业试验现象做了进一步分析。结果表明：当预精轧温度为944℃时,试验钢网状碳化物的析出时刻全部处于快速冷却阶段,球化退火后渗碳体颗粒均匀细小,网状级别可降低至1.5级,布氏硬度为202.72,强韧性能均较高,满足GB/T18254－2002《高碳铬轴承钢》和实际生产对GCr15轴承钢退火材的要求。     

稀土钼塑性加工力学分析

在TTS-820热模拟试验机上,分析稀土钼的高温变形特征,其变形温度为1100—1400℃,变形速度为1-50s^-1,变形程度为0—0．6,并对其进行塑性变形抗力的研究,采用非线性回归方法建立稀土钼的变形抗力模型,获得了稀土钼的变形抗力曲线图,对不同的数学模型结构进行回归比较,提出拟合精度高的变形抗力的数学模型,该模型具有较高的精度及良好的数值稳定性。