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1.
Y. Qu X. He X. Zhang H. Fu X. Cheng X. Liu 《Materialwissenschaft und Werkstofftechnik》2020,51(7):930-937
Heat treatment is of great significance to the performance improvement of high speed steel. Via heat treatment, the microstructure of high speed steel can be improved, thus greatly improving the material performance. The effect of tempering temperature on the microstructure of aluminium-bearing high boron high speed steel (AB-HSS) was investigated by optical microscope (OM), scanning electron microscope (SEM) and x-ray diffraction (XRD). The hardness and wear resistance of the alloy at different tempering temperatures were tested by Rockwell hardness tester, micro-hardness tester and wear tester. The experimental results indicate that the tempering microstructure of aluminium-bearing high boron high speed steel consists of α-Fe, M2B and a few of M23(C, B)6. Tempering temperature could greatly affect the wear resistance of materials. With the increase of tempering temperature, the wear resistance of aluminium-bearing high boron high speed steel firstly increase and then decrease. The alloy tempered at 450 °C has the best wear resistance and minimum wear weight loss. This study provides a reference for the formulation of heat treatment process of aluminium-bearing high boron high speed steel. 相似文献
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针对一种以Al作为主要强化元素的新型马氏体时效不锈钢,通过力学性能测试、光学显微镜观察和透射电子显微分析方法,研究不同的热处理温度对实验钢力学性能和微观组织的影响。结果表明:该实验钢的抗拉强度最高可达1876MPa,屈服强度可达1762MPa,具有良好的强韧性配合。固溶处理后形成了具有高密度位错的细小板条马氏体组织,在时效过程中,马氏体基体上弥散析出的NiAl相使其强度得到大幅度的提升。随着时效温度的提高,NiAl析出相颗粒逐渐长大粗化,从而使强度在到达峰值后迅速下降,出现了过时效现象。实验钢经过820℃固溶+(-70℃)冷处理+540℃时效处理后可获得良好的综合力学性能。 相似文献
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Nb–V additions clearly affected the precipitation state, respective phase transformations and final microstructure, and in turn, resulting mechanical properties of an intercritically annealed transformation induced plasticity sheet steel. As the precipitation hardening played a limited role in the overall strengthening, the grain refinement was the prevailing strengthening mechanism associated with the addition of the Nb–V microalloying to a basic TRIP780 composition. In addition to this, the microstructural changes, resulting from the addition of microalloying, lowered the stability of retained austenite, which decreased the elongation of the steel. Nevertheless, using this microalloying concept, an exceptional product of RmxA80 exceeding 16?000 MPa % could be achieved. 相似文献
4.
Yuanyuan Song Xiuyan Li Lijian RongYiyi Li 《Materials Science and Engineering: A》2011,528(12):4075-4079
The influence of tempering temperature on the reversed austenite formation and tensile properties are investigated in Fe-13%Cr-4%Ni-Mo low carbon martensite stainless steel in the temperature range of 550-950 °C. It is found that at the temperatures below 680 °C, the reversed austenite formation occurs by diffusion. Amount of the reversed austenite is determined by the tempering temperature and the holding time. The segregation of Ni is the main reason for the stability of the reversed austenite. When the temperatures are above 680 °C, the reversed austenite formation proceeds by diffusionless. The reversed austenite will transform back to martensite after cooled to room temperature. The tensile properties are most strongly influenced by the amount of the reversed austenite obtained at room temperature. The excellent combination of good strength and ductility is at 610 °C. 相似文献
5.
Mg-12Li, Mg-12Li-3(Al-Si), Mg-12Li-7(Al-Si) and Mg-12Li-9(Al-Si) alloys (all in wt%) were fabricated by high frequency vacuum induction melting in a water cooled copper crucible. After subsequently hot-rolling and annealing, their microstructure and mechanical properties were investigated. Experimental results show that mechanical properties of Mg-12Li alloy were significantly improved by the addition of Al-Si eutectic alloy. Mg-12Li-7(Al-Si) alloy shows the highest strength of 196 MPa of the investigated alloys, which is about 1.8 times of the strength of Mg-12Li alloy, and maintains high elongation of 27%. The improved mechanical property with addition of Al and Si in the eutectic proportion into Mg-12Li alloy was attributed to the solution strengthening effect of Al and precipitation hardening effect from AlLi and Mg2Si precipitates. 相似文献
6.
《Materials Science & Technology》2013,29(10):1273-1279
AbstractThe effect of tempering on nitrided austenitic stainless steel AISI 316 has been studied. Nitrided specimens (with 0.4 wt-%N) were tempered for short times at temperatures up to 900°C and the results show a small effect on the microstructures and mechanical properties. The strength is consistent with a Hall–Petch relationship dependent on nitrogen content in solution. The effect of tempering has also been studied on cold and hot deformed nitrided specimens. In these cases, tempering had a range of different effects on the microstructures and mechanical properties. Specimens that are tempered before cold rolling showed a continuous decrease in strength as the tempering temperature increased, while specimens cold rolled and then tempered had a maximum strength at 550°C. Specimens with 0.4 wt-%N subjected to tempering followed by hot deformation also showed a maximum strength at similar tempering temperatures. The nature of these changes has been analysed and mechanisms have been proposed that relate microstructural effects and properties. 相似文献
7.
In this paper, the precipitates formed during the tempering after quenching from temperature 1150 °C for 7.90Cr–1.65Mo–1.25Si–1.2V steels are investigated using an analytical transmission electron microscope (A-TEM).The study of this tempering is carried out in isothermal and anisothermal conditions, by comparing the results given by dilatometry and hot hardness.Tempering is performed in the range of 300–700 °C. Coarse primary carbides retained after heat treatment are V-rich MC and Cr–Mo-rich M7C3 types. In turn, it gives a significant influence on the precipitation of fine secondary carbides, that is, secondary hardening during tempering. The major secondary carbides are Cr–Mo–V-rich M′C (and/or) Cr–Mo-rich M2C type. The peak hardness is observed in the tempering range of 450–500 °C. In the end, we observe between 600 and 700 °C, that this impoverished changes the phase. At these high temperatures of tempering, we observe that there is a carbide formation of the types M6C developing at the expense of the fine M7C3 carbides previously formed. 相似文献
8.
The alloy AISI 630 (ASTM A564‐89 17‐4 PH) is a precipitation hardening stainless steel with good mechanical and corrosion properties. Mechanical properties strongly depend on the microstructure. Namely, the formation of the reversed austenite and coarsening of copper rich precipitates cause a substantial drop of hardness. Thus, the evolution of the microstructure during ageing was thoroughly investigated in order to explain the processes that have effect on formation of the reversed autenite. The reaustenitization was analyzed with a dilatometer, while the coarsening of copper rich precipitates was observed by transmission electron microscope. The amount of austenite was measured with x‐ray diffraction and the impact of austenite on the fracture appearance transition temperature was observed. It was found that the amount of the so called reverse austenite does not only depend on the amount of transformed austenite but also on its chemistry, as it dictates its ability to transform into martensite during cooling. 相似文献
9.
The effect of tempering temperature on mechanical properties and microstructure of low alloy Cr and CrMo steel 总被引:1,自引:0,他引:1
Two low alloy Cr and CrMo steels with similar levels of carbon, manganese and chromium have been studied to determine the effect of tempering temperature on the mechanical properties and microstructure. The quenching and tempering of steels were carried out using a high-speed dilatometer. The steels were quenched at the average cooling rate of 30 K s-1 in the temperature range from 1123 to 573 K by flowing argon and tempered at 673, 823 and 973 K. The martensite of steels formed during quenching was of entire lath morphology with 2 vol% retained austenite. It was found that after tempering at 973 K the Cr steel contained only orthorhombic cementite, while the CrMo steel contained the cementite and hexagonal Mo2C particles in the ferrite matrix. At the same tempering conditions, the CrMo steel shows higher strength but lower ductility as compared to those of Cr steel. It is shown that this difference results from finer prior austenite grain, substructure within matrix and precipitate dispersion strengthening, primarily by Mo2C. Transmission electron microscopy (TEM) bright- and dark-field micrographs as well as selected area diffraction pattern analysis of orientation relationship showed that the cementite precipitated from the ferrite matrix. Fractography analysis showed that the morphology fracture surface was changed by increasing tempering temperature. Tempering at 973 K obtained ductile fracture by the microvoid coalescence mechanism. 相似文献
10.
The present study aims to investigate the effect of grain refinement on strain hardening behaviour and fracture surface characteristics in 316LN austenitic stainless steel (ASS). The ASSs with varying grain sizes were obtained through 90% cold rolled reduction and subsequently phase reversion annealing treatment. The results showed that the grain refinement from coarse-grained (CG) structure to ultrafine-grained (UFG) structure increased the yield strength whilst maintaining a reasonable ductility. The strain hardening curves in all the samples were divided into three stages. The fractures in all the samples were ductile fracture with dimples. The subtle differences in the strain hardening behaviour and fracture surface characteristics among the samples with various grain sizes from CG structure to UFG structure were influenced by the deformation mechanisms of austenite. 相似文献
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This paper presents the results of an investigation on autogeneous laser welding of AISI 420 stainless steel to kovar alloy using a 100 W pulsed Nd:YAG laser. The joints had a circular geometry and butt welded. The joints were examined by optical microscope for cracks, pores and for determining the weld geometry. The microstructure of the weld and the heat affected zones were investigatedby scanning electron microscope. The austenitic microstructure was achieved in the weld. The morphology of weld zone solidification was basically cellural, being influenced by the temperature gradient. It was found that the start of solidification in the kovar side of weld zone occurred by means of epitaxial growth. When the temperature gradient was high, the columnar grains were created in the fusion boundary of 420 stainless steel side toward weld zone. Measurements taken by X-ray spectrometry for dispersion of the energy in the weld zone indicated a significantly heterogeneous distribution of chromium element. The variations in chemical compositions and grains morphologies significantly alter the Vickers microhardness values in the weld zone. 相似文献
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Hot compression tests were carried out in the semi-solid state of 9Cr18 stainless steel on Gleeble-1500 thermal simulation testing machine to investigate the effects of thixoforming parameters on its microstructure and mechanical properties. In this paper, microstructure was observed by scanning electron microscopy (SEM) and analyzed using energy dispersive spectrometer (EDS), and true stress–stain curves of the specimens with different initial microstructures after thixoforming were obtained to study the deformation mechanism. The results showed that thixoforming parameters such as reheating temperature and the strain rate had a significant influence on microstructure and mechanical properties evolution of 9Cr18 semi-solid billet. With increasing reheating temperature or decreasing strain rate, average size of carbides decreased from 2 μm to 0.5 μm, and the phenomenon of liquid extrusion during thixoforming became more obvious. During thixoforming, carbon atoms diffused to molten metal from austenite in the centre of specimens. When thixoforming temperature reached 1300 °C, martensitic transformation occurred after rapid cooling. Flow stress of semi-solid billet was lower than traditional ingot casting and hot rolled state steel, when reheated to the semi-solid range, due to their different original microstructure. 相似文献
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W.F. Cui S.X. Zhang Y. JiangJ. Dong C.M. Liu 《Materials Science and Engineering: A》2011,528(21):6401-6406
A low carbon bainitic steel with Cu-P alloying was developed. The new steel aims to meet the demand of high strength, high toughness and resistance to chloride ion corrosion for the components used in the environment of sea water and oceanic atmosphere. Mechanical properties of the steel were tested and strengthening and toughening mechanisms were analyzed by comparing hot-rolled microstructures of the low carbon bainitic steels with and without Cu-P alloying. The results show that Cu-P alloying provided strong solution strengthening with weak effect on ductility. The toughness loss caused by Cu-P alloying could be balanced by increasing the amount of martensite/remained austenite (M/A island) at lower finishing temperature. The static recovery process during rolling interval was delayed by the interaction of phosphorous, copper atoms with dislocations, which was favorable to the formation of bainitic plates. Super-fine Nb(C, N) particles precipitated on dislocations had coherency with bainite ferrite at 830 °C finishing temperature. Raising finishing temperature to 880 °C, Nb(C, N) particles were prone to coarsening and losing coherency. It was also found that no accurate lattice match relationship among retained austenite, martensite and bainite in granular bainitic microstructure. 相似文献
18.
Effect of brazing temperature on tensile strength and microstructure for a stainless steel plate-fin structure 总被引:1,自引:0,他引:1
This paper presented a vacuum brazing technology for 304 stainless steel plate-fin structures with BNi2 filler metal. The effect of brazing temperature on tensile strength and microstructure has been investigated. The tensile strength is increased along with the increasing of brazing temperature. The microstructure is very complex and some Boride compounds are generated in the brazed joint. Full solid solution can be generated in the middle zone of joint when the brazing temperature is increased to 1100 °C. The brittle phases always exist in the fillet no matter how the brazing temperature changes, but the microstructure in fillet becomes more uniform and the tensile strength is increased with the brazing temperature increasing. In total, the brittle Boride compounds are decreased with the brazing temperature increase. Brazing with a filler metal thickness 105 μm and 25 min holding time, 1100 °C is the best suitable brazing temperature and a tensile strength of 82.1 MPa has been achieved for 304 stainless steel plate-fin structure. 相似文献
19.
Effect of Ni content on the tensile properties and strain-induced martensite transformation for 304 stainless steel 总被引:1,自引:0,他引:1
The effect of Ni content (8.3-12 wt.%) on the tensile properties and strain hardening behavior was studied on type 304 stainless steels (STS) used for the membrane of LNG storage tanks. The tensile test temperature was varied from 25 °C to −196 °C. At room temperature, the hardening and ductility indices (tensile strength, strain hardening exponent and elongation) increased with decreasing Ni content. For the 8.3-9.0 wt.% Ni STS, a lower yield point was observed at temperatures below −60 °C. It was due to the dynamic strain softening and/or transformation-induced plasticity (TRIP) that accompanied the rapid increase in the amount of strain-induced martensite (α′) at low strains. Neither dynamic strain softening nor TRIP was observed for the 12 wt.% Ni STS because only the ?-martensite transformation was produced at the low strains. 相似文献
20.
H.F.G. de Abreu A.D.S. Bruno S.S.M Tavares R.P. Santos S.S. Carvalho 《Materials Characterization》2006,57(4-5):342-347
AISI 444 is a Mo-alloyed ferritic stainless steel which presents good naphthenic corrosion resistance, making it attractive for applications in petroleum refining plants; however, good formability is also important. To achieve good formability with this alloy the annealing process is crucial. The annealing temperature in ferritic stainless steel is usually around 850 °C, which falls in the range of sigma phase precipitation. A means to avoid this precipitation is to anneal at temperatures around 1000 °C followed by rapid cooling. Annealing at high temperatures can cause grain growth and carbide or nitride precipitation which can result in a reduction of room temperature toughness. In this paper, the rolling and recrystallization textures of AISI 444 steel were studied in samples cold rolled with different thickness reductions (30%, 60%, 80% and 90%) followed by annealing at 955, 980 and 1010 °C. Aspects of grain size and carbide precipitation after annealing were characterized using EBSD and AFM. The material drawability was analyzed through strain rate or Lankford (r) coefficients calculated from texture results. 相似文献