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1.
Uma Batra S. Ray S. R. Prabhakar 《Journal of Materials Engineering and Performance》2003,12(4):426-429
The variation in the austempered microstructure, the volume fraction of retained austenite, Xλ, the average carbon content of retained austenite, Cλ, their product XλCλ and the size of bainitic ferrite needles with austempering temperature for 0.6% Cu alloyed ductile iron have been investigated
for three austempering temperatures of 270, 330, and 380 °C for 60 min at each temperature after austenitization at 850 °C
for 120 min. The austempering temperature not only affects the morphology of bainitic ferrite but also that of retained austenite.
There is an increase in the amount of retained austenite, its carbon content, and size of bainitic ferrite needles with the
rise in austempering temperature. The influence of austempering time on the structure has been studied on the samples austempered
at 330 °C. The increase in the austempering time increases the amount of retained austenite and its carbon content, which
ultimately reaches a plateau. 相似文献
2.
1.IntFOdUction AustemPered Duetile Iron(ADI)15 a relatively newmaterial in east alloy family.Its mierostrueture eonsists ofaeieular ferrite in a high earbon austenite matrix ealledausferrite.This very fine mierostrueture offers 相似文献
3.
高性能球墨铸铁在汽车底盘轻量化中的应用 总被引:1,自引:0,他引:1
介绍了高性能球墨铸铁的发展现状及优异性能,并结合汽车轻量化需求,分析了等温淬火球墨铸铁材料在汽车底盘上的应用趋势,最后介绍了等温淬火球墨铸铁在实际生产中的应用。 相似文献
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6.
《中国铸造》2016,(5):361-367
Measurements of dry sliding wear are presented for ductile irons with composition Fe-3.56C-2.67Si-0.25Mo-0.5Cu and Ni contents of 0.8 and 1.5 in wt.% with applied loads of 50, 100 and 150 N for austempering temperatures of 270, 320, and 370 °C after austenitizing at 870 °C for 120 min. The mechanical property measurements show that the grades of the ASTM 897M: 1990 Standard can be satisfied for the selected austempering conditions. The results show that wear resistance is independent of austempering temperature with an applied load of 50 N, but there is a strong dependence at higher austempering temperatures with applied loads of 100 and 150 N. Observations indicate that wear is due to subsurface fatigue with cracks nucleated at deformed graphite nodules. 相似文献
7.
Shot peening is one of the most common surface treatments to improve the fatigue behavior of metallic parts. In this study the effect of shot peening process on the fatigue behavior of an alloyed austempered ductile iron (ADI) has been studied. Austempering heat treatment consisted of austenitizing at 875℃ for 90 min followed by austempering at three different temperatures of 320, 365 and 400℃. Rotating-bending fatigue test was carried out on samples after shot peening by 0.4-0.6 mm shots. XRD and SEM analysis, micro hardness and roughness tests were carried out to study the fatigue behavior of the samples. Results indicate that the fatigue strengths of samples austempered at 320, 365 and 400℃ are increased by 27.3%, 33.3% and 48.4%, respectively, after shot peening process. 相似文献
8.
O. Eric Cekic M. Dojcinovic D. Rajnovic L. Sidjanin S. Balos 《International Journal of Cast Metals Research》2018,31(5):279-287
In this paper, the study of cavitation behaviour of austempered ductile iron (ADI) alloyed with copper, as well as copper and nickel with a fully ausferritic microstructure, is presented. The ADI materials used were austenitized at 900 °C and austempered at 350 °C having an ausferrite microstructure with 16 and 19% of austenite, respectively. The experimental investigations were conducted using the ultrasonically induced cavitation test method. The results show that the cavitation damage was initiated at graphite nodules, as well as in the interface between a graphite nodule and an ausferrite matrix. The cavitation rate revealed that the ADI material alloyed with Cu + Ni austempered at 350 °C/3 h has a higher cavitation resistance in water than ADI alloyed with Cu. An increased cavitation resistance of the ADI material alloyed with Cu and Ni is due to the matrix hardening by stress assisted phase transformation of austenite into the martensite (SATRAM) phenomenon. 相似文献
9.
L. Bartosiewicz I. Singh F. A. Alberts A. R. Krause S. K. Putatunda 《Journal of Materials Engineering and Performance》1995,4(1):90-101
An investigation was carried out to examine the influence of microstructure and chromium on the tensile properties and plane
strain fracture toughness of austempered ductile cast iron (ADI). The investigation also examined the growth kinetics of ferrite
in these alloys. Compact tension and round cylindrical tensile specimens were prepared from ductile cast iron with Cr as well
as without Cr. These specimens were then given four different heat treatments to produce four different microstructures. Tensile
tests and fracture toughness tests were carried out as per ASTM standards E-8 and E-399. The crack growth mechanism during
fracture toughness tests was also determined.
The test results indicate that yield strength, tensile strength, and fracture toughness of ADI increases with an increase
in the volume fractions of ferrite, and the fracture toughness reaches a peak when the volume fractions of the ferrite are
approximately 60% in these alloys. The Cr addition was found to reduce the fracture toughness of ADI at lower hardness levels
(<40 HRC); at higher hardness levels (≥40 HRC), the effect of chromium on the fracture toughness was negligible. The crack
growth mechanism was found to be a combination of quasi-cleavage and microvoid coalescences, and the crack trajectories connect
the graphite nodules along the way. 相似文献
10.
关于奥贝球铁及其微观组织术语的探讨—对ADI(AustemperedDuctileIron)我们需要一个正确的中文术语 总被引:13,自引:2,他引:13
论述了等温淬火球铁的工艺及其微观组织。分析了其微观组织与钢中贝氏体的区别。指出ADI(Austempered Ductile Iron)奥贝球铁是一个恰当的术语。对这种新铸铁,我们需要一个正确的中文术语:奥铁球铁或者称奥氏体等温淬火球铁。 相似文献
11.
The effect of sub-zero cooling on microstructure and mechanical properties of a low alloyed austempered ductile iron has been investigated. Austempering of samples was performed at 325℃and 400℃after austenitizing at 875℃and 950℃. The sub-zero treatments were carried out by cooling down the samples to -30℃, -70℃and -196℃. The changes in volume fraction of austenite and mechanical properties were determined after cooling to each temperature. The austenite volume fraction of samples which were austenitized at 875℃and austempered at 325℃remained unchanged, whilst it reduced in samples austenitized at 950℃and 875℃for austempering temperature of 400℃. In these specimens, some austenite transformed to martensite after subzero cooling. Mechanical property measurements showed a slight increase in strength and hardness and decrease in elongation and toughness due to this transformation behavior. 相似文献
12.
Mikhail V. Riabov Yury S. Lerner Mohammed F. Fahmy 《Journal of Materials Engineering and Performance》2002,11(5):496-503
Impact properties of standard American Society for Testing Materials (ASTM) grades of austempered ductile iron (ADI) were
evaluated at subzero temperatures in unnotched and V-notched conditions and compared with ferritic and pearlitic grades of
ductile irons (DIs). It was determined that there is a decrease in impact toughness for all ADI grades when there is a decrease
in content of retained austenite and a decrease in test temperature, from room temperature (RT) to −60 °C. However, the difference
in impact toughness values was not so noticeable for low retained austenite containing grade 5 ADI at both room and subzero
temperatures as it was for ADI grade 1. Furthermore, the difference in impact toughness values of V-notched specimens of ADI
grades 1 and 5 tested at −40 °C was minimal. The impact behaviors of ADI grade 5 and ferritic DI were found to be more stable
than those of ADI grades 1, 2, 3, and 4 and pearlitic DI when the testing temperature was decreased. The impact toughness
of ferritic DI was higher than that of ADI grades 1 and 2 at both −40 °C and −60 °C. The impact properties of ADI grades 4
and 5 were found to be higher than that of pearlitic DI at both −40 °C and −60 °C. The scanning electron microscopy (SEM)
study of fracture surfaces revealed mixed ductile and quasicleavage rupture morphology types in all ADI samples tested at
both −40 °C and −60 °C. With decreasing content of retained austenite and ductility, the number of quasicleavage facets increased
from ADI grade 1–5. It was also found that fracture morphology of ADI did not experience significant changes when the testing
temperature decreased. Evaluation of the bending angle was used to support impact-testing data. Designers and users of ADI
castings may use the data developed in this research as a reference. 相似文献
13.
A detailed review of wear resistance properties of austempered ductile iron (ADI) was undertaken to examine the potential
applications of this material for wear parts, as an alternative to steels, alloyed and white irons, bronzes, and other competitive
materials. Two modes of wear were studied: adhesive (frictional) dry sliding and abrasive wear. In the rotating dry sliding
tests, wear behavior of the base material (a stationary block) was considered in relationship to countersurface (steel shaft)
wear. In this wear mode, the wear rate of ADI was only one-fourth that of pearlitic ductile iron (DI) grade 100-70-03; the
wear rates of aluminum bronze and leaded-tin bronze, respectively, were 3.7 and 3.3 times greater than that of ADI. Only quenched
DI with a fully martensitic matrix slightly outperformed ADI. No significant difference was observed in the wear of steel
shafts running against ADI and quenched DI. The excellent wear performance of ADI and its countersurface, combined with their
relatively low friction coefficient, indicate potential for dry sliding wear applications. In the abrasive wear mode, the
wear rate of ADI was comparable to that of alloyed hardened AISI 4340 steel, and approximately one-half that of hardened medium-carbon
AISI 1050 steel and of white and alloyed cast irons. The excellent wear resistance of ADI may be attributed to the strain-affected
transformation of high-carbon austenite to martensite that takes place in the surface layer during the wear tests. 相似文献
14.
The effect of austenitizing conditions on the microstructure and impact properties of an austempered ductile iron (ADI) containing
1.6% Cu and 1.6% Ni as the main alloying elements was investigated. Impact tests were carried out on samples of initially
ferritic matrix structure and which had been first austenitized at 850,900, 950, and 1000°C for 15 to 360 min and austempered
at 360°C for 180 min.
Results showed that the austenitizing temperature, Tγ, and time, tγ, have a significant effect on the impact properties of the alloy. This has been attributed to the influence of these variables
on the carbon kinetics.
The impact energy is generally high after short tγ, and it falls with further soaking. In samples austenitized at 850 and 900°C, these trends correspond to the gradual disappearance
of the pro-eutectoid ferrite and the attainment of fully developed ausferritic structures. In initially ferritic structures,
the carbon diffusion distances involved during austenitization are large compared to those in pearlitic structures. This explains
the relatively long soaking periods required to attain fully ausferritic structures, which in spite of the lower impact energy
values, have a better combination of mechanical properties.
Microstructures of samples austenitized at 950 and 1000°C contain no pro-eutectoid ferrite. The impact properties of the former
structures are independent of tγ, while those solution treated at 1000°C are generally low and show wide variation over the range of soaking time investigated.
For fully ausferritic structures, impact properties fall with an increase in Tγ. This is particularly evident at 1000°C. As the Tγ increases, the amount of carbon dissolved in the original austenite increases. This slows down the rate of austenite transformation
and results in coarser structures with lower mechanical properties. Optimum impact properties are obtained following austenitizing
between 900 and 950°C for 120 to 180 min. 相似文献
15.
Jincheng Liu 《International Journal of Cast Metals Research》2013,26(3):189-195
Austempering kinetic measurements and mechanical property measurements are reported for irons with different Mn contents and different nodule counts after austenitising at 870 °C and austempering at 375 °C. It is shown that increasing nodule count, which reduces segregation and changes the size and distribution of intercellular boundaries, increases the interphase boundary area between graphite and matrix and decreases the continuity of the unreacted austenite in the intercellular boundary. This accelerates the stage I reaction which broadens the heat treatment window and moves it to earlier austempering times. A high nodule count can be used to counter the delay of the stage I reaction caused by Mn additions used to increase the hardenability of the iron. A high nodule count produces a finer, more uniform ausferrite structure that increases the strength, ductility and impact energy of the austempered iron. 相似文献
16.
J. Achary 《Journal of Materials Engineering and Performance》2000,9(1):56-61
A new processing method was investigated for improving the strength and elongation of austempered ductile iron (ADI) by grain
refinement of parent austenite using thermomechanical treatment. The material was deformed at the austenitization temperature
by single and multipass rolling before the austempering treatment. The effects of the amount of deformation, austenitization
temperature, austempering temperatures, reaustenitization, and secondary deformation on the tensile properties were studied.
The properties obtained using the method were compared with those of the ASTM standards. The effect of deformation on the
graphite shape was also studied. Tensile strength/yield strength/elongation values were found to increase with increasing
austenite deformation up to 40% and then to start decreasing. Tensile strength/yield strength and elongation values of 1700
MPa/1300 MPa/5% and 1350 MPa/920 MPa/15% can be achieved with this method in the ranges of variables studied. 相似文献
17.
The effects the leading factors bearing on fatigue limits were investigated with three kinds of ductile iron specimens various
microstructures. As a result of examination, the fatigue limits in relationship to hardness and tensile strength, the expected
higher improvement for fatigue limits in the case of the high strength specimens that experienced austempering treatment are
not observed in comparison with the specimens treated with stress relief treatment. The estimated maximum defect size is one
of the important parameters in predicting and evaluating fatigue limits for three different heat-treated ductile cast irons.
Also, a quantitative relationship can be established between the fatigue limit and maximum defect size. Moreover, it is possible
to explain the difference in fatigue limits in the three ductile cast irons by application of the rates of non-propagating
crack which connects the adjacent graphite nodules before it stops. 相似文献
18.
Effect of austempering time on mechanical properties of a low manganese austempered ductile iron 总被引:1,自引:0,他引:1
Susil K. Putatunda Pavan K. Gadicherla 《Journal of Materials Engineering and Performance》2000,9(2):193-203
An investigation was carried out to examine the influence of austempering time on the resultant microstructure and the room-temperature
mechanical properties of an unalloyed and low manganese ductile cast iron with initially ferritic as-cast structure. The effect
of austempering time on the plane strain fracture toughness of this material was also studied. Compact tension and round cylindrical
tensile specimens were prepared from unalloyed ductile cast iron with low manganese content and with a ferritic as-cast (solidified)
structure. These specimens were then austempered in the upper (371 °C) and lower (260 °C) bainitic temperature ranges for
different time periods, ranging from 30 min. to 4 h. Microstructural features such as type of bainite and the volume fraction
of ferrite and austenite and its carbon content were evaluated by X-ray diffraction to examine the influence of microstructure
on the mechanical properties and fracture toughness of this material.
The results of the present investigation indicate that for this low manganese austempered ductile iron (ADI), upper ausferritic
microstructures exhibit higher fracture toughness than lower ausferritic microstructures. Yield and tensile strength of the
material was found to increase with an increase in austempering time in a lower bainitic temperature range, whereas in the
upper bainitic temperature range, time has no significant effect on the mechanical properties. A retained austenite content
between 30 to 35% was found to provide optimum fracture toughness. Fracture toughness was found to increase with the parameter
(XγCγ/d)1/2, where Xγ is the volume fraction of austenite, Cγ is the carbon content of the austenite, and d is the mean free path of dislocation motion in ferrite. 相似文献
19.
A numerical, non steady state microsegregation model is used to predict the extent of solute segregation in a ductile cast iron. The microsegregation of Mn and Mo to intercellular boundaries is shown to depend on the nodule count and the local solidification time. It is suggested that increased nodule count is the most effective way of reducing intercellular segregation in thicker components. 相似文献
20.
Effects of nickel and processing variables on the mechanical properties of austempered ductile irons
This study investigates the effects of inoculation techniques, ingate numbers and raw materials on the mechanical properties of ADIs. Five batches of base ductile irons (DI1-DI5) were poured to produce stepped plate castings following designated processing variables. DI1 and DI2 were used to compare the effect of raw materials on the sulphur content of irons and the resulting properties. DI1 and DI4 were produced in order to study the effect of nickel; DI3 and DI5 were poured to evaluate the effect of ingate numbers; DI4 and DI5 were poured to study the effect of inoculation techniques. Effects of these variables on the mechanical properties and microstructures of as-cast and austempered ductile irons (ADIs) were evaluated respectively.Using a given magnesium content (0.033–0.047 wt%), ADIs with a high percentage of sulphur, in the range of 0.004–0.02 wt%, developed a higher percentage elongation. ADIs alloyed with 0.48 wt% Cu, 0.46 wt% Ni and a minimum level of sulphur (0.004 wt%) produced a lower degree of deviation in strength, elongation and impact energy but showed the greatest deviation in the tested hardness of the stepped plate castings. Stream inoculation improved the nodule counts and nodularity of base ductile irons but also introduced dross and/or unreacted inoculant within the stepped plate casting. This was detrimental to the tested elongation of ADIs taken from the stepped plate casting. Two-step austempering treatment could significantly improve the tested elongation of ADIs without significantly affecting the developed strength. 相似文献