Ductile Iron Castings

The accurate prediction of scientific and statistical parameters depends, largely, on the functional correlation between the variables involved, as well as their definite and predictable behaviour around the line of best fit (the regression line). Hence, an accurate and reliable prediction of the fracture toughness and mechanical properties of glass fibre reinforced polypropylene (GFPP) composites is very important in order to prevent sudden failure of components fabricated from them. It also gives the opportunity to save cost on experimentation. Three grades of polypropylene (PP) of different molecular weights (MW) had glass fibre reinforcements each. The incorporation of maleic anhydride grafted PP (MA-g-PP) into the composites was for compatibilisation between the matrix and reinforcements. There was tensile testing on both the un-notched and notched dumbbell samples. The use of J-Integral analysis was to investigate the fracture toughness of the composites. There was an evaluation of the effect of different MW of PP on the fracture toughness and impact properties of the composites. The examination of the morphology of the materials was by (SEM), while charge coupled device (CCD) camera monitored crack propagation behaviour under tensile loading. There was further morphology study to analyse the fibre length distribution and interfacial shear strength of the composites. Investigations revealed that the composite with the lowest MW PP consistently showed better mechanical, impact and fracture toughness properties than those with higher MW PP. It was also observed that incorporating MA-g-PP as compatibilisers had greater interfacial bonding effects, resulting in higher interfacial shear strength in GFPP of lower MW and high melt flow rates than those of higher MW and low melt flow rate. The investigation further revealed that as the MW of PP decreased, the fracture toughness and other mechanical properties increased in a linear correlation. Crack propagation trailed the interface between PP matrix and GF because of weak bonding in the composite with higher MW PP. This study revealed that incorporating MA-g-PP into GFPP composites achieved better properties with PP of lower MW and higher melt flow rate. Hence the mechanical and fracture properties of GFPP depend largely on the MW of the polymer PP matrix. There was a strong linear correlation observed between the MW of PP, fracture toughness and other impact properties thereby making it possible to make a reliable prediction of any property of the composites from another.

<div class="htmlview paragraph">The objective of this work is to test and develop monotonic tensile properties and strain controlled fatigue properties of a cast ductile iron. The test data and the related material constants will be used in conjunction with vehicle loading data to perform finite element stress-strain analysis and fatigue life prediction analysis to aid in the design of automotive components made from ductile iron. Currently, such material property data does not exist in the literature for this particular grade of ductile iron.</div> <div class="htmlview paragraph">Monotonic tension and fully reversed strain controlled fatigue tests were conducted by following ASTM E-8, ASTM E-606, and SAE J-1099 on samples machined from the cast ductile iron. Monotonic tensile properties were obtained, including Young's modulus, yield strength, ultimate tensile strength, elongation, reduction in area, strength coefficient K, and strain hardening exponent n. Fully reversed strain controlled fatigue properties were also obtained, including cyclic strength coefficient K′, cyclic strain hardening exponent n′, Young's Modulus as a function of fatigue cycles, mean stress as a function of cycles, fatigue strength coefficient, fatigue strength exponent, fatigue ductility coefficient, and fatigue ductility exponent. Four repetitive tests were conducted at each strain level. The ductile iron showed cyclic hardening behavior. Fatigue life scatter was about a factor of two for the five strain amplitude levels tested.</div> <div class="htmlview paragraph">Chemistry, microstructure, hardness, nodularity and nodule count was characterized for the ductile iron. Finally fractography analysis was done using a scanning electron microscope which revealed the fatigue region and transgranular cleavage fracture region on the fracture surface of tested samples. Fracture toughness of the ductile iron was estimated using the stress intensity factor equation of a surface crack in a solid round bar under tension and based on the fatigue crack depth at fast fracture and the maximum stress applied.</div> <div class="htmlview paragraph">In conclusion, monotonic tension and strain controlled fatigue tests were successfully performed. The fatigue performance of the material was characterized, and the material's fatigue properties will be used in durability design and fatigue life prediction.</div>

Influence of the microstructure on fatigue and fracture toughness properties of large heat-treated mold steels

Characterization and modeling of the mechanical behavior of high silicon ductile iron

This research is directed towards studying the effect of semi-solid processing (using cooling plate tech- nique) on the microstructure, fluidity, and mechanical properties of ductile iron (DI). Sand mold castings with constant width of 25 mm and length of 150 mm with the thicknesses of 6, 12, 18, and 25 mm were used in this study. Microstructure, fluidity, and tensile strength prop- erties were investigated as a function of fraction of solid. The results indicated that by increasing fraction of solid microstructure becomes finer and more globular. However, increasing primary fraction of solid increases the cementite content in the matrix. Above a certain fraction of solid (fs = 0.28, fs = 0.1, and fs = 0.05 for 25, 18, and 12 mm wall thickness, respectively), the fluidity of semi-solid processed DI decreases steeply. For low fraction of solid (fs B 0.15), increasing the fraction of solid results in an increment in the tensile strength, comparing with the ordinary DI due to the fine and globular structure forma- tion. Any further increment of fraction of solid (fs ( 0.15) leads to the cementite increment and gas porosity forma- tion, consequently the tensile strength decreased. The fraction of solid of DI and casting wall thickness should be considered in order to obtain the best combination of microstructure, fluidity, and mechanical properties of semi- solid processed DI.

The mechanical properties of ductile iron (DI) and compacted graphite iron (CGI) are measured and reported on standard machined specimens (as per ASTM). However, most castings retain most of the as-cast surface. This surface layer (the casting skin) includes both surface and subsurface features. Because of the casting skin, the mechanical properties of the part are typically significantly lower than those found on standard ASTM machined specimens.

Tensile, fracture toughness and crack growth properties of a roll-extruded HP 9Ni-4Co-25C steel alloy

Influence of matrix structure on the fatigue properties of an alloyed ductile iron

There is continuous demand for local production of quality automobile spare parts in the country nowadays. The current economic condition of the nation has placed more challenges on the indigenous foundry to improve on their technology to make automobile spare components accessible and affordable to the nation. This study examined the possibility of converting the indiscriminately dumped sleeve scraps from state of waste to ductile iron useful products thereby adding value to it. The mechanical properties of ductile iron produced from the sleeve scraps using local technology were determined and found comparable to that of international standard (ISO). Sleeve scraps were charged with graphite and FeSi into a rotary furnace and melted. Nodularization was achieved ising MgFeSi as an indigenous technology of the production process. The hypotheses of the study were tested and compared with the ISO standard of the grade of ductile iron and the findings revealed that Ductile iron that corresponds with the standard was successfully produced from solid waste (automobile sleeves scraps). It was recommended among others that the effort be made towards the conversion of sleeve scraps to ductile iron automobile components, in order to minimize the menace of environmental pollution which leads to numerous health hazards and mortality. Also, making automobile spare parts available to the end users and reduce its importation

: The report provides a vital portion of the basic engineering data necessary for the design of reliable and efficient airframe structures involving electron-beam weldments in titanium alloys. Tensile, fracture toughness, and subcritical crack growth properties of both base metal and weldments have been obtained for 1- and 2-in. Ti-6Al-4V and 1-in. Beta III plate. Test temperatures ranged from -65F to 175F and the test environments included laboratory air, water, salt water and JP-4 jet fuel. The concept of stress intensity factors from linear elastic fracture mechanics is used to quantitatively assess the load carrying capacity and crack growth resistance of the test materials. Fracture toughness and tensile properties are tabulated while the fatigue crack propagation and stress corrosion cracking rates are presented in a graphic format.

Extended finite element simulation on Tensile, fracture toughness and fatigue crack growth behaviour of additively manufactured Ti6Al4V alloy

The effect of aluminum (0, 2, 4, and 6 wt. %) and copper (0, 2, 4, and 6 wt. %) on graphite morphology, microstructure and compressive behavior of ductile iron specimens manufactured by sand casting technique were investigated. The graphite morphology and microstructure were evaluated using optical microscopy (OM) and scanning electron microscopy (SEM) equipped image processing software. To study the mechanical properties, the compression test was conducted on the ductile iron specimens. The results indicated that the surface fraction and nodule count of graphite decreased when the amount of aluminum increased from 0 to 2 wt. % and after that from 2 to 6 wt. %. In addition, the nodularity of graphite increased with the increment of the aluminum amounts. By adding the amount of copper, the surface fraction and nodule count of graphite increased and nodularity of graphite decreased. The addition of aluminum and copper decreased the surface fraction of ferrite and increased the surface fraction of pearlite in the microstructure. By increasing the amounts of aluminum and copper, compressive stress vs. strain curves were shifted upwards, and modulus of elasticity, yield strength, maximum compressive stress, and fracture strain improved. In comparison with copper, aluminum had a greater influence on the mechanical properties of ductile iron.

This paper investigates the effects of silicon content above 3 wt% and different cooling rates on the graphite morphology and the mechanical properties of ductile cast iron. To research and determine these effects, three grades of high-silicon ductile iron were cast with silicon content of 3 wt%, 3.5 wt% and 4.5 wt%. In order to investigate the effect of different cooling rates during solidification, four sections with different thicknesses were cast in the same mold, i.e., cube with wall thickness 180 mm and standard Y2, Y3 and Y4 keel blocks. Microstructure analysis and tensile test were performed on the as-cast samples. In the second step of analysis, detailed metallographic observations on specially prepared samples were performed in order to investigate the risk of graphite degeneracy appearance, especially chunky graphite formation due to high silicon content and its effect on mechanical properties. The results showed that graphite content, ferrite fraction, yield strength and tensile strength were increased by increasing the silicon content. On the other hand, elongation decreases with increasing silicon content. Also, based on the metallographic observations of the present work, the risk of chunky graphite formation increases with increase in silicon content and with decrease in the cooling rate. Chunky graphite formation affects negatively mechanical properties, especially elongation in ductile cast irons with silicon content higher than 3.5 wt%.

The reactor vessels of the nuclear production reactors at the Savannah River Site (SRS) were constructed in the 1950's from Type 304 stainless steel plates welded with Type 308 stainless steel filler using a multipass metal-inert-gas process. A mechanical properties database for irradiated material has been developed for the vessel with materials from archival primary coolant system piping irradiated at low temperatures (75 to 150°C) in the State University of New York at Buffalo reactor (UBR) and the High Flux Isotope Reactor (HFIR) to doses of 0.065 to 2.1 dpa. Fracture toughness, tensile, and Charpy-V impact properties of the weldment components (base, weld, and weld heat-affected-zone (HAZ)) have been measured at temperatures of 25°C and 125°C in the L-C and C-L orientations for materials in both the irradiated and unirradiated conditions for companion specimens. Fracture toughness and tensile properties of specimens cut from an SRS reactor vessel sidewall with doses of 0.1 and 0.5 dpa were also measured at temperatures of 25 and 125°C. The irradiated materials exhibit hardening with loss of work hardenability and a reduction in toughness relative to the unirradiated materials with a slight sensitivity to exposure. Irradiation increased the yield strength between 22% to 187% with a concomitant tensile strength increase between-9% to 29%. The irradiation-induced decrease in the elastic-plastic fracture toughness (JD at 1 mm crack extension) is between 26% to 64%; the range of JICvalues are 72.8 to 366 kJ/m2 for the irradiated materials. Similarly, Charpy V-notch results show a 38% to 59% decrease in impact absorbed energies. The C-L orientation shows significantly lower absorbed energies and fracture toughness parameters than the L-C orientation for both the base and HAZ components in both the unirradiated and irradiated conditions.

The influence of prior cold work on tensile properties, fatigue crack growth rates and fracture toughness of Incoloy 908 was examined at 293°K and 4.2°K. Fatigue crack growth rates were measured using a constant AK technique. Crack length was determined using compliance. Fracture toughness was determined by the J-integral technique. Properties following heat treatment were compared for two starting conditions: (1) solution annealed at 980°C for 1, hour and (2) solution annealed followed by 20% cold work. Three heat treatments were studied: (1) aging at 650°C for 200 hours, (2) aging at 700°C for 100 hours, and (3) aging at 750°C for 50 hours.