scholarly journals Effect of Thermal Cycle on Microstructure Evolution and Mechanical Properties of Selective Laser Melted Low-Alloy Steel

Materials ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 3625
Author(s):  
Xueliang Kang ◽  
Shiyun Dong ◽  
Hongbin Wang ◽  
Shixing Yan ◽  
Xiaoting Liu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Brittle Fracture ◽  
Alloy Steel ◽  
Lower Bainite ◽  
Granular Bainite ◽  
Low Alloy Steel ◽  
Traditional Methods ◽  
Average Grain Size ◽  
Solidification Microstructures

Low-alloy steel samples were successfully fabricated by selective laser melting (SLM). The evolution of the microstructure and the mechanical properties were investigated with different values of the energy area density (EAD). The results revealed that the initial solidification microstructures of the single tracks with different EADs were all martensite. However, the microstructures of bulk samples under different EADs were not martensite and differed significantly even from one another. When EAD increased from 47 to 142 J/mm2, the mixed lower bainite and martensite austenite microstructure changed to granular bainite; further, the morphology of bainite ferrite gradually changed from lath to multilateral. Moreover, with the increase of EAD, the grain size was remarkably reduced because of the increasing austenitizing periods and temperature during thermal cycling. The average grain size was 1.56 µm, 3.98 µm, and 6.31 µm with EADs of 142 J/mm2, 71 J/mm2, and 47 J/mm2, respectively. Yield strength and tensile strength of the SLM low-alloy steel increased with the increase in EAD; these values were significantly more than those of the alloys prepared by traditional methods. The microstructure of the SLM low-alloy steel samples is not uniform, and the inhomogeneity becomes more significant as EAD decreases. Simultaneously, when EAD decreases, the fracture mechanism changes from ductile to a mixture of ductile and brittle fracture; this is in contrast to the samples prepared by traditional methods. This study also found a stress concentration mechanism around large pores during plastic deformation that resulted in a brittle fracture. This indicates that large-sized pores significantly degrade the mechanical properties of the specimens.

Comparison of the strengthening effects of Nb, V, and Ti on the mechanical properties of 20MnSi low-alloy steel

2020 ◽  
Vol 111 (6) ◽  
pp. 504-510
Author(s):  
Qingxiao Zhang ◽  
Qing Yuan ◽  
Wenwei Qiao ◽  
Guanghui Chen ◽  
Guang Xu
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Grain Refinement ◽  
Alloy Steel ◽  
Precipitation Strengthening ◽  
Strengthening Effect ◽  
Strengthening Mechanisms ◽  
Low Alloy Steel ◽  
Average Grain Size ◽  
Base Steel

Abstract Three alloys, containing niobium, vanadium and titanium, respectively, were refined and the strengthening effect attained after adding them individually in a 20MnSi low-alloy rebar steel was investigated. The results show that the strengthening effect attained due to the addition of niobium is the best, whereas that due to the addition of titanium is the poorest. Grain refinement and precipitation strengthening are the main strengthening mechanisms observed in niobium-steel and vanadium-steel, whereas only precipitation strengthening is observed in titanium-steel. Moreover, the average grain size of niobium-steel is the smallest among the four types of steels, while the size of ferrite and pearlite microstructures show almost no obvious change as compared to the base steel in the case of titanium-steel. Furthermore, the volume fractions of ferrite and pearlite in the four tested steels have no noticeable change.

Investigation of Microstructure and Mechanical Properties of Ultra High Strength Bainitic Steel

2013 ◽  
Vol 313-314 ◽  
pp. 77-81
Author(s):  
M.H. Sheikh Ansari ◽  
M. Aghaie-Khafri
Keyword(s):  
Mechanical Properties ◽  
Alloy Steel ◽  
High Strength ◽  
Lower Bainite ◽  
Good Combination ◽  
Bainitic Steel ◽  
Low Alloy Steel ◽  
Tempered Martensite ◽  
Medium Carbon ◽  
Bainitic Steels

In this study, medium carbon low alloy steel was used to obtain bainitic structures. The lower bainite and tempered martensite-lower bainite structures were achieved by isothermal austempering and up quenching treatment, respectively. Based on the results obtained these structures showed a very good combination of strength and toughness. Furthermore, it has been shown that austenitization time and temperature, as well as austempering time and temperature play a major role in achieving ultra-high strength bainitic steels.

The Development of Processing to Mechanical Property Relationships via Quantitative Microstructure Assessment in Low Alloy Steel Heavy Section Forging Materials

2011 ◽  
Author(s):  
Daniel J. Cogswell
Keyword(s):  
Mechanical Properties ◽  
Mechanical Property ◽  
Alloy Steel ◽  
Phase Particle ◽  
Secondary Phase ◽  
Visual Assessment ◽  
Numerical Comparison ◽  
Low Alloy Steel ◽  
Heavy Section ◽  
Average Grain Size

This paper provides details of an ongoing effort to characterise the microstructure of heavy section low alloy steel forgings used in high integrity applications and correlate these data to the mechanical properties of these materials. Current industry practice is to use chemical etching and visual assessment in acceptance standards to determine nominal averages for microstructure parameters. This work uses electron microscope techniques to provide information on a variety of grain and secondary-phase particle information allowing numerical comparison of key microstructure variables to mechanical properties. For instance, the transition toughness behaviour of low alloys steels is controlled by the combination of the largest grain and particle in the material, i.e. the most potent initiator for cleavage failure. Knowledge of only the average grain size is insufficient to correlate microstructure and transition toughness performance. The programme consists of three main stages: modelling key variables in the manufacturing process to predict microstructure from thermodynamic predictions, developing quantitative microstructure data on archive materials for which mechanical property data are known to allow empirical relationships to be constructed and, a final validation exercise of a complete model by production and assessment of trial forgings.

Characteristics of Deformation-Induced Transformation in Steel 2.25Cr1Mo

2008 ◽  
Vol 385-387 ◽  
pp. 509-512
Author(s):  
Qing Fen Li ◽  
Hong Bin Chen
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Alloy Steel ◽  
Volume Fraction ◽  
Controlled Rolling ◽  
Low Alloy Steel ◽  
Cooling Process ◽  
Controlled Cooling ◽  
Steel Microstructure ◽  
Steel Strength

Characteristics of deformation-induced transformation (DIT) in the refractory low alloy steel 2.25Cr1Mo were experimentally studied. Effect of different controlled-rolling and controlled-cooling process on the steel microstructure and mechanical properties were investigated and the mechanism was discussed. Results show that the grain size and the ferrite volume fraction were obviously affected by the rolling and cooling processes. Proper DIT technique may significantly accelerate the transformation of austenite to ferrite in the steel and improve the steel strength.

scholarly journals Wear-Resistance Improvement of 65Mn Low-Alloy Steel through Adjusting Grain Refinement by Cyclic Heat Treatment

Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7636
Author(s):  
Ying Tong ◽  
Yu-Qing Zhang ◽  
Jiang Zhao ◽  
Guo-Zheng Quan ◽  
Wei Xiong
Keyword(s):  
Heat Treatment ◽  
Grain Size ◽  
Wear Resistance ◽  
Grain Refinement ◽  
Alloy Steel ◽  
Low Alloy Steel ◽  
Cyclic Heat Treatment ◽  
Average Grain Size ◽  
Cyclic Heat ◽  
Cyclic Quenching

Refined microstructures achieved by cyclic heat treatment significantly contribute to improving the wear resistance of steels. To acquire the refined microstructures of 65Mn low-alloy steel, first, the specimens were solid solution-treated; then, they were subjected to cyclic heat treatment at cyclic quenching temperatures of 790–870 °C and quenching times of 1–4 with a fixed holding time of 5 min. The mechanical properties of 65Mn low-alloy steel in terms of hardness, tensile strength, elongation and wear resistance were characterized. Afterwards, the effect of cyclic heat treatment on microstructure evolution and the relationships between grain refinement and mechanical properties’ improvement were discussed. The results show that the average grain size firstly decreased and then increased with the increase in the quenching temperature. Hardness increased with grain refinement when the temperature was lower than 830 °C. Once the temperature exceeded 830 °C, hardness increased with the temperature increase owing to the enrichment of carbon content in the martensite. With the increase in cyclic quenching times, hardness continuously increased with grain refinement strengthening. In addition, both tensile strength and elongation could be significantly improved through grain refinement. The relationships among wear loss, hardness and average grain size showed that wear resistance was affected by the synthesis reaction of grain refinement and hardness. Higher hardness and refined grain size contributed to improving the wear resistance of 65Mn low-alloy steel.

scholarly journals The Influence of Austenite Grain Size on the Mechanical Properties of Low-Alloy Steel with Boron

Metals ◽  
2017 ◽  
Vol 7 (1) ◽  
pp. 26 ◽  
Author(s):  
Beata Białobrzeska ◽  
Łukasz Konat ◽  
Robert Jasiński
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Alloy Steel ◽  
Low Alloy Steel ◽  
Austenite Grain Size ◽  
Austenite Grain

Effect of the Strain Rate on Mechanical Properties and Microstructure of High Strength Low Alloy Steel HC340LA

2012 ◽  
Vol 217-219 ◽  
pp. 467-470
Author(s):  
Xiao Hang Liu ◽  
Wen Jing Yuan ◽  
Hao Bin Tian ◽  
Fa Xi Diao
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Tensile Strength ◽  
Strain Rate ◽  
Alloy Steel ◽  
High Speed ◽  
Hsla Steel ◽  
High Strength ◽  
Static Tension ◽  
Low Alloy Steel

The mechanical properties and microstructure of the high strength low alloy HC340LA were obtained with different strain rate. The research shows that the better plasticity, higher tensile strength and yield ratio can be found in high speed tensile state than in quasi-static tension. The plasticity and tensile strength decrease with the increasing of the strain rate during the high speed tension. With the increasing of the strain rate, the grain size of the ferrite decreases and its distribution is uneven, and the grain boundaries increases. The HSLA steel HC340LA submit to obvious Ductile Frecture mechanism. The size of the dimples is more uniform, bigger and deeper with the strain rate 50 s-1 than with the strain rate 200 s-1. Therefore, the higher strain rate with over strain rate 50 s-1 has less Superscript textcontribution to the improvement of plasticity of the HSLA steel HC340LA.

Surface Modification and its Influence on the Microstructure and Creep Resistance of Nickel Based Superalloy René 77 / Modyfikacja Powierzchniowa Oraz Jej Wpływ Na Mikrostrukture I Wytrzymałosc Na Pełzanie Odlewów Z Nadstopu Niklu Ren´E 77

2013 ◽  
Vol 58 (1) ◽  
pp. 95-98 ◽  
Author(s):  
M. Zielinska ◽  
J. Sieniawski
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Surface Modification ◽  
Turbine Blades ◽  
Processing Parameters ◽  
Grain Structure ◽  
Creep Tests ◽  
Cobalt Aluminate ◽  
Nickel Based Superalloy ◽  
Average Grain Size

Superalloy René 77 is very wide used for turbine blades, turbine disks of aircraft engines which work up to 1050°C. These elements are generally produced by the investment casting method. Turbine blades produced by conventional precision casting methods have coarse and inhomogeneous grain structure. Such a material often does not fulfil basic requirements, which concern mechanical properties for the stuff used in aeronautical engineering. The incorporation of controlled grain size improved mechanical properties. This control of grain size in the casting operation was accomplished by the control of processing parameters such as casting temperature, mould preheating temperature, and the use of grain nucleates in the face of the mould. For nickel and cobalt based superalloys, it was found that cobalt aluminate (CoAl2O4) has the best nucleating effect. The objective of this work was to determine the influence of the inoculant’s content (cobalt aluminate) in the surface layer of the ceramic mould on the microstructure and mechanical properties at high temperature of nickel based superalloy René 77. For this purpose, the ceramic moulds were made with different concentration of cobalt aluminate in the primary slurry was from 0 to 10% mass. in zirconium flour. Stepped and cylindrical samples were casted for microstructure and mechanical examinations. The average grain size of the matrix ( phase), was determined on the stepped samples. The influence of surface modification on the grain size of up to section thickness was considered. The microstructure investigations with the use of light microscopy and scanning electron microscopy (SEM) enable to examine the influence of the surface modification on the morphology of ’ phase and carbides precipitations. Verification of the influence of CoAl2O4 on the mechanical properties of castings were investigated on the basis of results obtained form creep tests.

Sign in / Sign up

Export Citation Format

Share Document