Nunghee RYU
,
Sunggoon KANG
材料科学技术（英）
The effects of laser hardening parameters such as beam power, beam diameter and scanning rate on microstructure and hardness of 9CrSi steel were investigated. The microstructure of the surface layer of 9CrSi steel was changed from pearlite to martensite, retained austenite and carbide by laser hardening. The depth of the hardened layer increased with increasing laser energy density and the surface hardeness increased by 3~5 times as high as the untreated steel. The laser hardened surface had good wear resistance due to martensite and carbide in the surface layer. The wear mode at low speed was abrasive, while the wear mode at high speed was adhesive.
关键词:
Laser hardening
,
null
,
null
,
null
A.Fallahi
材料科学技术（英）
The purpose of this research is to quantify the effects of compositional and processing parameters on the microstructure and properties of dual phase steel produced directly by hot rolling and rapid cooling.Steels with the base composition of 0.1%C, 1.4%Si, and 1.0%Mn with additions of 0.5%Cr to influence hardenability, 0.04%Nb to retard recrystallization in the latter stages of rolling, or 0.02%Ti to inhibit grain growth during and after reheating were investigated. Investigation was made to predict microstructure evolution and to correlate microstructure with processing parameters. The effects of the important microstructure parameters such as ferrite grain size, martensite volume fraction (VM) and morphology (polygonal or fibrous) on the tensile and impact properties are discussed. Multiple linear regression analysis of the ultimate tensile strength has shown that, increasing VM and martensite microhardness and grain refinement of ferrite are the major contributions to increase the strength of the steel. It was found that the dual-phase steel produced by controlled rolling process, with a microstructure which consisted of fine grained ferrite (4 mm) and 35%´40% fibrous martensite, presented optimum tensile and impact properties because of enhanced resistance to crack propagation.
关键词:
Dual-phase steel
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null
,
null
Baoqun NING
,
Yongchang LIU
,
Qingzhi SHI
材料科学技术（英）
The influences of thermal stabilization of austenitic on the onset temperature for a martensite transformation in T91 ferritic heat-resistant steel were studied by high-resolution differential dilatometer. The phase transformation kinetic information was obtained by adopting lever rule from the recorded dilatometric curves. The results show that an inverse stabilization, featured by the damage of “the atmosphere of carbon atoms” and the increase of the starting temperature for martensite transformation takes place when the T91 ferritic steel is isothermally treated above the Ms point, and it becomes strong with increasing the holding time. While the continued temperature for martensite transformation decreases gradually when isothermally holding at a temperature below Ms point. The observed inverse stabilization behavior could be attributed to the relatively high temperature of Ms point in the explored T91 ferritic heat-resistant steel.
关键词:
T91 ferritic heat-resistant steel
,
奥氏体热稳定化
,
碳原子气
沈贇靓
,
闵娜
,
谢尘
,
吴晓春
上海金属
利用XRD、高分辨透射电镜等试验方法,结合内耗法研究深冷处理对80Cr9Mo2钢回火特性影响.结果表明:深冷处理前低温回火将导致部分碳原子由马氏体相扩散至残留奥氏体相中,提高残留奥氏体稳定性.而回火前深冷处理将导致更多残留奥氏体相变为低温马氏体,马氏体相(包括低温马氏体相)含量增加,可动位错密度提高,位错处偏聚间隙碳原子含量提高.有利于回火过程中析出更多数量的细小碳化物,这是深冷处理提高耐磨性能的主要原因.
关键词:
80Cr9Mo2钢
,
深冷处理
,
残留奥氏体
,
马氏体
,
位错
,
内耗
栾佰峰
,
薛姣姣
,
柴林江
,
周军
稀有金属材料与工程
锆合金β相冷却组织对于发展高性能燃料包壳具有至关重要的作用.本工作从冷却速率和杂质元素两个影响因素出发,对核反应堆用锆合金β→α转变组织的相关研究进行了综述.锆合金的马氏体转变为无扩散的切变过程,不产生表面浮凸,Ms不随冷却速率变化.成分相同时,随着β冷却速率的增加,锆合金微观结构按如下次序变化:Lenticular组织→Parallel-plate魏氏组织→Basketweave魏氏组织→马氏体.相同冷却速率下,当杂质元素参与形成难溶的第二相时,会促进Basketweave组织的形成,而当这些元素提高β转变温度时,则倾向于促进Parallel-plate组织的形成.
关键词:
锆合金
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冷却速率
,
马氏体
,
魏氏组织
,
杂质元素
