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The effects of Mo and Ni on the microstructure and properties of compacted graphite iron were investigated experimentally, especially with regard to the thermal conductivity at elevated temperature. It was found that the ferrite fraction is weakly affected by Mo content but significantly reduced by Ni addition. Moderate content of Mo is beneficial to the tensile strength and the elongation, but it is detrimental for the thermal conductivity, which is more obvious than Ni. The phenomenon that thermal conductivity increases and then decreases at elevated temperature, which is named temperature dependence, could be connected with the lattice distortion of the matrix caused by solute atoms. With the addition of Mo or Ni, the rising amplitude of thermal conductivity increases as well as the temperature corresponding to the maximal of thermal conductivity. Besides, the effects of Mo on the temperature dependence of thermal conductivity are higher when compared with Ni. [ABSTRACT FROM AUTHOR]

The V and W modified Cr19 series duplex stainless steels with transformation induced plasticity (TRIP) have been newly developed and the effects of microstructures on room temperature mechanical properties have been investigated. The addition of ferrite forming elements V and W slightly increases the volume fraction of ferrite phase from about 55% to 57–60%, however, the cold rolling process hardly influence the fraction. When the duplex phases exhibit a coarse banding morphology before cold rolling, the ultimate tensile strength and elongation are improved significantly with the addition of V and W elements mainly due to the occurrence of TRIP effect. The ultimate tensile strength and yield strength of Cr19+V increase very slightly, but the elongation increases to about 61% after cold rolling. Both the ultimate tensile strength and elongation of Cr19+W significantly increase to about 800 MPa and 67%, respectively. The improvement is attributed to TRIP effect and refinement of banded ferrite and austenite phases. After aging heat treatment, the precipitate of VN and Cr 23 C 6 particles contributes to the further increase of ultimate tensile strength to about 1000 and 920 MPa of Cr19+V and Cr19+W DSSs, respectively. Strain induced αʹ-martensite is transformed from austenite directly with an orientation relationship. The strengthening behaviors have been discussed based on the microstructural evolutions. [ABSTRACT FROM AUTHOR]

(1 − x)(0.1BiYbO-0.9PbTiO)- xPb(YbNb)O (PYN-BYPT) ceramics were prepared by the conventional solid state reaction. The effect of Pb(YbNb)O content on the microstructure and electrical properties of ceramics was investigated. The results show that there are two phases, perovskite phase and pyrochlore phase (YbTiO), coexisting in PYN-BYPT ceramics when the content of Pb(YbNb)O increases from 0.1 to 0.3 mol. With increasing Pb(YbNb)O content, the pyrochlore phase YbTiO increases, T decreases and d increases firstly and then decreases. When the content of Pb(YbNb)O increases from 0.4 to 0.9 mol, perovskite phase and pyrochlore phase (PbNbO) coexists in the ceramics. The contents of PbNbO and the T decrease. PYN-BYPT ceramics with 0.2 mol Pb(YbNb)O show the optimal piezoelectric properties, with ε of 231.4, tan δ of 0.015, d of 20 pC/N, and T of 523.2 °C, which makes it a promising material for high-temperature (up to 500 °C) piezoelectric applications. [ABSTRACT FROM AUTHOR]

The previous studies have revealed that addition of different elements in TbDyFe alloys have different influences on its microstructure, mechanical and magnetic properties. According to the effects, one can classify elements into different groups. This paper aims to explain the differences by the enthalpy of mixing between the atomic pairs. Various alloys of the type Tb 0.3 Dy 0.7 Fe 2 , (Tb 0.3 Dy 0.7 ) 0.3 Fe 0.6 Co 0.1 , (Tb 0.3 Dy 0.7 ) 0.3 Fe 0.6 Cu 0.1 , (Tb 0.3 Dy 0.7 ) 0.3 Fe 0.6 Nb 0.1 , (Tb 0.3 Dy 0.7 ) 0.3 Fe 0.6 Ti 0.1 , (Tb 0.3 Dy 0.7 ) 0.3 Fe 0.6 V 0.1 were prepared by an arc melting under a high-purity argon atmosphere. The effects of Co, Cu, Nb, Ti, V addition on the microstructure, mechanical properties and magnetic properties of TbDyFe alloys were studied systematically. The results showed that according to the different mixing enthalpy between different atom-pairs, the elements added in TbDyFe alloy could be classified into two different groups. One had a more negative mixing enthalpy with the rare earth element Tb(Dy), such as Co, Cu, which were prone to form phases with rare earth elements; the others possessed a more negative enthalpy of mixing with Fe, such as Nb, Ti, V, which were conducive to react with Fe. With Co, Cu element addition, the alloys exhibited dendritic morphology. While the alloys demonstrated the second phase precipitation morphology with addition of Nb/Ti/V elements. Compared to the Tb 0.3 Dy 0.7 Fe 2 alloy, the REFe 3 phase appeared in the alloys with addition of Co/Cu element. The NbFe 2 /Fe 2 Ti/FeV phase precipitated in the alloys with Nb/Ti/V addition, respectively. But the formation of REFe 3 phase was effectively suppressed due to the addition of Nb/Ti/V elements. The presence of both REFe 3 phases and NbFe 2 /Fe 2 Ti/FeV paramagnetic phases all reduced the magnetostriction of (Tb 0.3 Dy 0.7 ) 0.3 Fe 0.6 M 0.1 (M = Co, Cu, Nb, Ti, V) alloys compared to the Tb 0.3 Dy 0.7 Fe 2 alloys. [ABSTRACT FROM AUTHOR]

The intrinsic brittleness in giant magnetostrictive material TbDyFe alloy has devastating influence on the machinability and properties of the alloy, thus affecting its applications. The purpose of this paper is to study the mechanical properties of the TbDyFe alloy by alloying with Nb element. The samples (Tb 0.3 Dy 0.7 ) x Fe 2x Nb y (y = 0, 0.01, 0.04, 0.07, 0.1; 3x + y = 1) were melted in an arc melting furnace under high purity argon atmosphere. The microstructure, magnetostrictive properties and mechanical performance of the alloys were studied systematically. The results showed that NbFe 2 phases were observed in the alloys with the addition of Nb. Moreover, both the NbFe 2 phases and rare earth (RE)-rich phases were increased with the increasing of Nb element. The mechanical properties results revealed that the fracture toughness of the alloy with the addition of Nb enhanced 1.5–5 times of the Nb-free alloy. Both the NbFe 2 phase and the RE-rich phase had the ability to prevent crack propagation, so that they can strengthen the REFe 2 body. However, NbFe 2 phase is a paramagnetic phase, which can reduce the magnetostrictive properties of the alloy by excessive precipitation. [ABSTRACT FROM AUTHOR]

The pore straightness of Gasar ingots was investigated through experiments and numerical simulation. The pore growth direction changes from diverging to convergent as the withdrawing speed increases, and straight pores are obtained when the solid/liquid interfaces are almost planar. The optimum withdrawing speed to obtain straight pores increases as the sample size decreases. Under optimum conditions, the average pore diameter of the small ingot is smaller than that of the large ingot, while the penetrative porosity of the large ingot is superior. The shape of the solid/liquid interfaces at the bottom of the ingot can be improved effectively by modifying the structure of the mold. Bridgman method is applicable for the fabrication of Gasar ingots with large size and high quality, and suitable sample size should be considered for different structural requirements. [ABSTRACT FROM AUTHOR]

0.83Pb(Zr 0.5 Ti 0.5 )O 3 − 0.11Pb(Zn 1/3 Nb 2/3 )O 3 − 0.06Pb(Ni 1/3 Nb 2/3 )O 3 (PZNNT) ceramics with different content of plate-like Sr 3 Ti 2 O 7 compound was prepared. Effect of Sr 3 Ti 2 O 7 amount and sintering temperature on the microstructures and piezoelectric properties of PZNNT ceramics were investigated. The results revealed that the content of tetragonal phase at morphotropic phase boundary (MPB) and grain size decreased significantly by increasing Sr 3 Ti 2 O 7 content. In addition, with further increase of sintering temperature for better density, the content of tetragonal phase and electric properties of PZNNT-5 wt%Sr 3 Ti 2 O 7 ceramics gradually increased. The optimal piezoelectric and dielectric properties of PZNNT-5 wt%Sr 3 Ti 2 O 7 ceramics sintered at 1040 °C for 2 h was d 33 = 572 pC/N, d 33 × g 33 = 17,630 × 10 –15 m 2 /N and k p = 0.57, which is potential candidate materials used for piezoelectric energy harvesting. [ABSTRACT FROM AUTHOR]

This paper describes a new method for optimizing the cellular structure of AlMg4Si8 alloy foams manufactured via powder metallurgy. The cellular structure was improved by pretreating TiH 2 with a layer of Sn powder, which was then remixed with an AlMg4Si8 alloy used as the raw material for the preparation of the precursor. TiH 2 was completely encapsulated in the molten Sn at an early stage of foaming when the matrix alloy was still solid, so that liberated H 2 was fully captured when TiH 2 began to decompose. The interpore flow of H 2 along the cracks in the solid matrix was avoided, improving the utilization ratio of TiH 2 as a blowing agent. After determining that 4.0 wt% Sn cladding was capable of almost completely encapsulating 0.5 wt% TiH 2 , the final cellular structure was optimized and regular circular pores were obtained. [ABSTRACT FROM AUTHOR]

HfMo 0.5 NbTiV 0.5 Si x (x = 0, 0.3, 0.5, 0.7) high-entropy alloys are synthesized by induction levitation melting with the aim of achieving a balanced combination of excellent strength at elevated temperature and reasonable ductility at room temperature (RT). The microstructure, phase evolution and compression mechanical properties of the alloys from 20 °C to 1200 °C are reported in this paper. It is found that the HfMo 0.5 NbTiV 0.5 matrix forms a simple disordered body-centered cubic (BCC) phase. After adding the Si element, multi-component silicide (Hf, Nb, Ti) 5 Si 3 is generated inside the alloys and exhibits a transition from hypoeutectic structure to eutectic structure and then to hypereutectic structure as the Si content increases. The addition of Si significantly improves the hardness and strength but reduces the ductility. At room temperature, The HfMo 0.5 NbTiV 0.5 and HfMo 0.5 NbTiV 0·5 Si 0.7 alloys show yield strengths of 1260 MPa and 2134 MPa, respectively, and the compressive mechanism transitions from ductile deformation to brittle fracture from x = 0 to x = 0.7. Strain softening and silicide segmentation are found to be typical during compression deformation of these alloys at elevated temperatures. In these conditions, the alloys survive at least 35% of engineering compression strain without fracture. During deformation at 1200 °C, the yield strengths of HfMo 0.5 NbTiV 0.5 and HfMo 0.5 NbTiV 0·5 Si 0.7 alloys are 60 MPa and 235 MPa, respectively. The attractive strength of the Si-containing alloys at elevated temperatures is strongly dependent on the strengthening effect caused by the silicides. [ABSTRACT FROM AUTHOR]

In this study, we investigated the effects of varied process parameters on the defect, molten pool morphologies, microstructures, and hardness of HX, and established the correlation based on the Hall-Petch relationship. The formation mechanism of different types of defects, which are formed by increasing energy density, is systematically explained. The dendritic/cellular structure analysis via detailed Scanning electron microscope (SEM) examination found that the size of dendritic arm spacing was affected significantly by varied energy densities. Higher energy input reduces the temperature gradient and solidification rate, which results in the increase of primary dendritic arm spacing (PDAS). In addition, the grain boundaries of dendrite can improve the mechanical properties, especially the hardness. The hardness test results show that the hardness value increased with the decrease of PDAS, which exhibited this linear relationship illustrated by the Hall-Petch relationship. [ABSTRACT FROM AUTHOR]

A refractory high-entropy alloy of HfNbTiVSi 0.5 was synthesized by induction levitation melting. The alloy is a composite composed mainly of a body centered cubic (BCC) solid solution and a multi-component silicide ((Hf, Nb, Ti)-Si). This alloy displays a balanced combination of strength at high temperature and ductility at room temperature. The studied results show that the compressive yield strength (YS) is as high as 1399 MPa, with a fracture strain of 10.9% at room temperature. At 800 °C and 1000 °C, the YS is still preserved at 875 MPa and 240 MPa, respectively, due to the higher load-carrying capacity of the silicide at elevated temperatures. Comparison to similar refractory HEAs shows that, the composite microstructure is beneficial for better room temperature strength and ductility as well as the elevated temperature properties. [ABSTRACT FROM AUTHOR]