Evaluation of the Role of Metallic Matrix on Environmentally Assisted Embrittlement of Austempered Ductile Iron (ADI) Using High Si Steel

In the present work, an evaluation of the volume fraction of austenite in austempered ductile iron (ADI) is presented by means of three different methods. Experimental tests were conducted on ADI samples after different austempering conditions and contained different volume fractions of the phase components in the metallic matrix (ferrite plates + austenite). A comparison of the volume fraction of austenite was carried out by metallographic magnetic methods using a variable field, as well as X-ray quantitative phase analysis. The main purpose of this work is to show the effectiveness of the proposed magnetic method for estimating the volume fraction of austenite in ADI cast iron. It is evident that the new method in which variable magnetic fields are used to quantify the phase composition exhibits very high accuracy within the second stage of the austempering transformation, in which the metallic matrix consists of ferrite plates and high-carbon austenite. Finally, this research shows that within the first and third stages the estimation of the volume fraction of the austenite is hampered by errors resulting from the presence of martensite (first stage) and carbide phases (third stage).

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The Influence of the Residual Mg Content in the Ductile Cast Iron on the Formation Law of Spherodial Graphite

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.415-417.907 ◽

2011 ◽

Vol 415-417 ◽

pp. 907-914 ◽

Cited By ~ 1

Author(s):

Zhi Qing Shen ◽

Hong Liang Zheng ◽

Tong Tong Li ◽

Yan Xu ◽

Rong Fu Xu ◽

...

Keyword(s):

Cast Iron ◽

Ductile Iron ◽

Metallic Matrix ◽

Ductile Cast Iron ◽

Holding Time ◽

Simple Substance ◽

Similar Composition ◽

Ratio Change ◽

Mg Content

The residual Mg content ,spherodize ratio and nuclei of spherodial graphites(abbreviated SG) were studied by casting a series of similar composition ductile iron rods and white samples with different holding time of spheroidizing. The results indicate that the residual Mg content in the ductile iron was less and less as the holding time grows ,which causing the morphology of graphites transfer from spherodial to oval. Spherodize ratio change law is not continuous as increasing the residual Mg content which is divided at the 0.02%. The morphologies of nuclei of SGs core are typical examples of the highly magnified structure of spherical and irregular polygons; the diameters are about 0.5~2μm, consisting of (Mg, Ca)S along with CeO2and MgO. Disregistry δ between the nucleus compounds and graphite are low,which indicates that nucleus compounds are good nucleating site for SGs.The Mg element in nuclei of SG just act as nucleation substrates.it is the Mg which maybe simple substance in the metallic matrix that act as the role of spherodizer determines the graphite shape.

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Role of austenite in promoting ductility in an austempered ductile iron

Materials Science and Technology ◽

10.1179/mst.1997.13.4.319 ◽

1997 ◽

Vol 13 (4) ◽

pp. 319-326 ◽

Cited By ~ 10

Author(s):

H. Bayati ◽

R. Elliott

Keyword(s):

Ductile Iron ◽

Austempered Ductile Iron

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Role of Bulky Retained Austenite in Austempered Ductile Iron

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1142.19 ◽

2017 ◽

Vol 1142 ◽

pp. 19-22 ◽

Cited By ~ 3

Author(s):

Chen Yang ◽

Xi Xi Cui ◽

Zhen Bo Zhao ◽

Gao Hua ◽

Cheng Liu

Keyword(s):

Fatigue Resistance ◽

Ductile Iron ◽

Retained Austenite ◽

Room Temperature ◽

Austempered Ductile Iron ◽

The Poor

In this investigation, the characteristics of bulky retained austenite in an austempered ductile iron are evaluated in two tempered conditions. which were intially tempered at 200oC for 1h before cooling to room temperature, and then tempered at 350oC for 1h. The result shows that the hardness within retained austenite areas is distributed unevenly with a range from 423 HV to 897 HV, which is attributed to the transformation from austenite to martensite during austempering. Also, the mechanism regarding the quenched marteniste formation is discussed. The poor fatigue resistance of ADI is hypothesized to be due to the amount of austenite transformed to martensite.

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AUSTEMPERING HEAT TREATMENT STUDY OF CAST DUCTILE IRON: ANALYSIS OF MECHANICAL AND MICROSTRUCTURAL PROPERTIES, ACCORDING TO THE A897M STANDARD SPECIFICATIONS FOR AUSTEMPERED DUCTILE IRON CASTINGS

Periódico Tchê Química ◽

10.52571/ptq.v15.n29.2018.64_periodico29_pgs_64_74.pdf ◽

2018 ◽

Vol 15 (29) ◽

pp. 64-74

Author(s):

A. R. M. SCHIFINO ◽

F. R. SANTANNA ◽

A. P. TRINDADE

Keyword(s):

Mechanical Properties ◽

Heat Treatment ◽

Cast Iron ◽

Ductile Iron ◽

Great Influence ◽

Metallic Matrix ◽

Nodular Cast Iron ◽

Austempered Ductile Iron ◽

Mechanical Resistance ◽

Spring Support

The objective of this work was to develop heat treatment parameters of an austempered cast iron alloy ASTM 897 / A 897M - 1400/1100/1, aiming at the production of a truck spring support. The austempered nodular cast iron, known by the acronym ADI - Austempered Ductile Iron - is a class of nodular cast iron that, after austempered thermal treatment, increases significantly its mechanical properties and tenacity (Machado, 2007). Mechanical and metallographic tests demonstrated the great influence that the level of microshrinkage has on the elongation and mechanical resistance of the material. Generally, tensile tests demonstrate high elongation due to minimal presence of microshrinkage and segregations in the metallic matrix of the material, as well as to the presence of austenite with high carbon retained in the ADI matrix. Analyzes were performed to determine if the mechanical properties required by ASTM 897 / A897M were achieved. Within this standard, four degrees can be obtained. The degree of interest in this study was 1400/1100/1, which is the grade requested by the company, so that the truck spring support can be put into service. Tensile, Charpy and optical microscopy tests were carried out.

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