Crack initiation mechanism in lanthanum-doped titanium-zirconium-molybdenum alloy during sintering and rolling

In the present study, a series of in situ TiB/Ti6Al4V composites were fabricated using selective laser melting. The formability, microstructure evolution and mechanical properties of the as-built samples added with different contents of TiB 2 were studied. It is found that the densification level is related to both the content of TiB 2 and laser energy density. The added TiB 2 reinforcement particle can spontaneously react with titanium and then form the TiB phase. The needle-like TiB phase tends to transform into dot-like particles with the decrease in energy density. Additionally, with the increase in TiB 2 content, the TiB phase is coarsened due to the increased nucleation rate and more reactions. The grain morphology is found to largely depend on the translational speed of solid-fluid interface determined by the temperature gradient and cooling rate. Also, the microhardness of the as-built TiB/Ti6Al4V composites is obviously improved. More interestingly, as the energy density increases, the microhardness of the as-built TiB/Ti6Al4V composites firstly increases and then decreases due to the synergy of grain size and different morphologies and distribution of TiB phases. The wear resistance of TiB/Ti6Al4V composites is far superior to that of Ti6Al4V alloy owing to the increased microhardness resulted from the uniform distribution of the hard TiB phase in the matrix.

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“…Similar cracking mechanism has also been illustrated in Ref. [25]. Figure 3d shows a short length of the crack near the end.…”

Section: Formability and Crackssupporting

confidence: 79%

Selective Laser Melting of In Situ TiB/Ti6Al4V Composites: Formability, Microstructure Evolution and Mechanical Performance

Luo

Liu

et al. 2020

Acta Metall. Sin. (Engl. Lett.)

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“…Among them, the most widely applied and potentially valuable is sheet metal processing, which has to be handled through rolling engineering [6]. Currently, there are two kinds of thermal deformation of molybdenum sheet: an unidirectional hot rolling (UHR) and a cross hot rolling (CHR), but a variety of defects are often accompanied by them, such as surface edge cracks and delamination [7][8][9]. Essentially, this is due to the serious genetic effect of passes and unreasonable control of processing parameters, the technical requirements are badly-needed.…”

Section: Introductionmentioning

confidence: 99%

Finite Element Analysis of Large Plastic Deformation Process of Pure Molybdenum Plate During Hot Rolling

Peng

Cheng

Xing

et al. 2021

Preprint

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Rare molybdenum resources have been increasingly involved in heavy industries. In this paper, the common unidirectional and cross hot rolling operations, for pure molybdenum plate, are numerically simulated by using MSC. Marc software. An elastic-plastic finite element model is employed together with updated Lagrange method to predict stress and strain fields in the work-piece. The results showed that there was a typical three-dimensional additional compressive stress ( σy > σx > σz ) in deformation zone, while strain could be divided into uniaxial compressive strain and biaxial tensile strain ( Ey > Ex > Ez ). Tensile stress σx increased with the accumulation of reduction and the decrease of friction coefficient at the edge of width spread. More importantly, the interlaced deformation caused by cross commutation was helpful to repair the severe anisotropy created by unidirectional hot rolling. By comparing the theoretical verification of rolling forces and the measured temperatures with the simulated values, eventually, it is demonstrated that the model is aligning well with the actual engineering.

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“…Generally, rolling is considered to be the preferred method of fabricating molybdenum and most of the sheet products [ 4 ] are completed in this way; however, this method can result in a variety of defects in the finished product. For example, a passive crack [ 5,6 ] is often initiated during rolling engineering, which is dependent on the adjustment and control of the processing parameters in the hot working conditions. The hot formation of pure molybdenum can be regarded as a multifactor function of deformation temperature ( T ), strain rate (

\overset{ε}{true}

), and strain ( ε ).…”

Section: Introductionmentioning

confidence: 99%

Rheological Behavior of Pure Molybdenum at High Temperature Considering Strain Compensation

Cheng

et al. 2020

Adv Eng Mater

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The rheological behavior of pure molybdenum at a temperature range of 1150–1300 °C at an interval of 50 °C with strain rates ranging from 0.01 to 10 s−1 is studied by means of an isothermal compression experiment. The obtained true stress–strain curves reflect the strong dependence of the flow stress on the deformation temperatures and strain rates. To accurately describe the rheological behavior, a classic Arrhenius‐type equation is utilized for verification, which has been developed to consider the strain compensation. The results show that the modified constitutive equation has the ability to accurately predict performance. Meanwhile, processing maps of pure molybdenum under strains of 0.3, 0.4, 0.5, and 0.6 are also constructed and the deformation safety in different domains is discussed in conjunction with the metallographic structure. The deformation conditions at a temperature range of 1250–1300 °C and a strain rate of 0.01–0.23 s−1 are the optimal hot working parameters under a strain of 0.6, which creates a foundation for the effective hot forming of molybdenum.

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Crack initiation mechanism in lanthanum-doped titanium-zirconium-molybdenum alloy during sintering and rolling

Cited by 26 publications

References 11 publications

Selective Laser Melting of In Situ TiB/Ti6Al4V Composites: Formability, Microstructure Evolution and Mechanical Performance

Selective Laser Melting of In Situ TiB/Ti6Al4V Composites: Formability, Microstructure Evolution and Mechanical Performance

Finite Element Analysis of Large Plastic Deformation Process of Pure Molybdenum Plate During Hot Rolling

Rheological Behavior of Pure Molybdenum at High Temperature Considering Strain Compensation

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