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austenite-to-ausferrite transformation

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Series: ASM Handbook
Volume: 1A
Publisher: ASM International
Published: 31 August 2017
DOI: 10.31399/asm.hb.v01a.a0006319
EISBN: 978-1-62708-179-5
.... The article reviews several factors, such as presence of graphite and austenite grain size, which affect the transformation rate of austenite during austempering of free-graphite cast irons. austenite austenite grain size austenite-to-ausferrite transformation bainite cast iron graphite heat...
Series: ASM Handbook
Volume: 1A
Publisher: ASM International
Published: 31 August 2017
DOI: 10.31399/asm.hb.v01a.a0006339
EISBN: 978-1-62708-179-5
... the martensite formation temperature, at which it is held while austenite partially transforms to ferrite without forming pearlite. The resulting matrix is a very fine-grained mixture of austenite and ferrite that combines good strength with ductility ( Ref 1 , Ref 2 , 3 ). The ASTM A897/A897-16, ISO 17804...
Series: ASM Handbook
Volume: 1A
Publisher: ASM International
Published: 31 August 2017
DOI: 10.31399/asm.hb.v01a.a0006322
EISBN: 978-1-62708-179-5
... Characteristics The basic structural differences between the ferritic, pearlitic, martensitic, and ausferritic classes are explained in Fig. 1 to 3 . Figures 1 and 2 are schematics of time-temperature transformation diagrams for continuous cooling and isothermal conditions, respectively. Figure 1...
Series: ASM Handbook
Volume: 1A
Publisher: ASM International
Published: 31 August 2017
DOI: 10.31399/asm.hb.v01a.a0006300
EISBN: 978-1-62708-179-5
... ferrite and pearlite, and the article “The Austenite-to-Ausferrite Transformation” covers bainite and martensite. In case ferrite appears, there is also some additional graphite that precipitates. Stable and Metastable Three-Phase Fields In the Fe-C phase diagram presented in “Thermodynamics...
Series: ASM Handbook
Volume: 4D
Publisher: ASM International
Published: 01 October 2014
DOI: 10.31399/asm.hb.v04d.a0005937
EISBN: 978-1-62708-168-9
.... This deterioration in properties is likely caused by the segregation of Mo to cell boundaries and the formation of carbides. The level of Mo should be restricted to not more than 0.30% in heavy section castings. Source: Ref 4 Fig. 18 Time to 5% transformed for a low-alloy ductile iron austenitized...
Series: ASM Handbook
Volume: 1A
Publisher: ASM International
Published: 31 August 2017
DOI: 10.31399/asm.hb.v01a.a0006294
EISBN: 978-1-62708-179-5
... higher strength and wear resistance. The difference between ausferrite and bainite is further discussed in “The Austenite-to-Ausferrite Transformation” article in this Volume. Fig. 26 Austempering process for cast iron. Source: Ref 34 The advantage of austempering is that it results...
Series: ASM Handbook
Volume: 1A
Publisher: ASM International
Published: 31 August 2017
DOI: 10.31399/asm.hb.v01a.a0006296
EISBN: 978-1-62708-179-5
... not affect the composition of the carbide phase. The designations of ferrite (α), austenite (γ), and Fe 3 C, therefore, can be used in the ternary system to identify the same phases that occur in the Fe-Fe 3 C binary system. However, silicon raises the transformation temperature range, decreases carbon...
Series: ASM Handbook
Volume: 1A
Publisher: ASM International
Published: 31 August 2017
DOI: 10.31399/asm.hb.v01a.a0006350
EISBN: 978-1-62708-179-5
..., then isothermally transformed at 280 °C (535 °F) for 2 h and air cooled. This transformation is never allowed to go to completion. It is believed that carbon diffuses from the ausferrite to the austenite, making it stable. The hardness of this specimen was 525 HV and 54.8 HRC. This is usually the lowest isothermal...
Book: Casting
Series: ASM Handbook
Volume: 15
Publisher: ASM International
Published: 01 December 2008
DOI: 10.31399/asm.hb.v15.a0005322
EISBN: 978-1-62708-187-0
... principal structures that develop during this continuous cooling are (in order) ferrite, pearlite, bainite, and martensite. Other matrix structures such as ausferrite may be formed during specialized heat treatments. Increased cooling rates cause the transformation of austenite to occur at increasingly...
Series: ASM Handbook
Volume: 4B
Publisher: ASM International
Published: 30 September 2014
DOI: 10.31399/asm.hb.v04b.a0005929
EISBN: 978-1-62708-166-5
... of the metal from the austenitizing temperature to a point above the martensite start (M s ) temperature, where it is held for a specified period of time, followed by cooling in air. This helps reduce distortion caused by uneven or nonuniform quenching, thermal stresses, and phase-transformation stresses...
Series: ASM Handbook
Volume: 1A
Publisher: ASM International
Published: 31 August 2017
DOI: 10.31399/asm.hb.v01a.a0006327
EISBN: 978-1-62708-179-5
... the Liquid/Solid Transformation” in this Volume ( Ref 7 , 8 ). The austenite commonly nucleates on the mold wall, resulting in columnar growth. At higher undercooling, the columnar-to-equiaxed transition occurs as the austenite nucleates on heterogeneities in the bulk liquid metal. The primary austenite...
Series: ASM Handbook
Volume: 1A
Publisher: ASM International
Published: 31 August 2017
DOI: 10.31399/asm.hb.v01a.a0006325
EISBN: 978-1-62708-179-5
... strength and are more ductile than pearlitic irons. However, for standard-grade ductile cast iron, ferritic/pearlitic grades are also common. The pearlite content depends on the cooling rate during the austenite-to-ferrite phase transformation at approximately 700 °C (1290 °F). In casting processes...
Book Chapter

By J.R. Keough
Series: ASM Handbook
Volume: 4A
Publisher: ASM International
Published: 01 August 2013
DOI: 10.31399/asm.hb.v04a.a0005820
EISBN: 978-1-62708-165-8
... are isothermally quenched for up to 24 h to achieve maximum properties. Austempered ductile iron (ADI) quench processes can range from 30 min to over 4 h to transform the microstructure from austenite to the acicular ferrite and carbon-stabilized austenite structure known as ausferrite . Step quenching...
Book: Casting
Series: ASM Handbook
Volume: 15
Publisher: ASM International
Published: 01 December 2008
DOI: 10.31399/asm.hb.v15.a0005324
EISBN: 978-1-62708-187-0
... sections will have a lower hardness and strength, unless the analysis is adjusted to compensate for the slower cooling, or unless the cooling rate of the casting is increased through the transformation temperature range. Heavier castings are often alloyed and/or heat treated to overcome this effect...
Series: ASM Handbook
Volume: 1A
Publisher: ASM International
Published: 31 August 2017
DOI: 10.31399/asm.hb.v01a.a0006306
EISBN: 978-1-62708-179-5
... of producing thin-wall castings with complicated geometries. The properties of the five ADI grades are given in Table 5 . An ideal ADI consists of acicular ferrite and carbon-stabilized austenite, also known as ausferrite; however, its actual microstructure can be more complicated ( Fig. 22...
Series: ASM Handbook
Volume: 1A
Publisher: ASM International
Published: 31 August 2017
DOI: 10.31399/asm.hb.v01a.a0006345
EISBN: 978-1-62708-179-5
... hardness and strength, unless the analysis is adjusted to compensate for the slower cooling, or unless the cooling rate of the casting is increased through the transformation temperature range. Heavier castings are often alloyed and/or heat treated to overcome this effect and achieve a higher strength...
Series: ASM Handbook
Volume: 4D
Publisher: ASM International
Published: 01 October 2014
DOI: 10.31399/asm.hb.v04d.a0005945
EISBN: 978-1-62708-168-9
.... Variations in cooling rate, from point to point, also can exaggerate the production of residual stresses because, in some instances, it is possible for austenite transformation products to be different in sections with different cooling rates. For example, in rapidly cooled sections in moderately alloyed...
Series: ASM Handbook
Volume: 9
Publisher: ASM International
Published: 01 December 2004
DOI: 10.31399/asm.hb.v09.a0003752
EISBN: 978-1-62708-177-1
...), which caused martensite to form in areas where the austenite stability was low. When martensite forms, it does so by a shear transformation that produces surface movement at a free surface. The specimen was brought back to room temperature, cleaned off, dried, and viewed with Nomarski DIC, producing...
Series: ASM Handbook
Volume: 9
Publisher: ASM International
Published: 01 December 2004
DOI: 10.31399/asm.hb.v09.a0003765
EISBN: 978-1-62708-177-1
... occurs due to the change in size of the plate martensite as transformation progresses. However, this is not the only factor, because some of the larger plates are also brown. There is only a very small amount of austenite, which surrounds the acicular ferrite at the graphite nodules and in the matrix...
Series: ASM Handbook
Volume: 1A
Publisher: ASM International
Published: 31 August 2017
DOI: 10.31399/asm.hb.v01a.a0006307
EISBN: 978-1-62708-179-5
..., it was concluded that a pure diffusion model was not sufficient to describe the transformation rate of austenite into ferrite and graphite, as previously proposed in the literature. By introducing an interfacial mass-transfer resistance at the graphite/ferrite interface, to control the incorporation rate of carbon...