In the exploration of fusion power, zirconium alloy has been viewed as a potential deuterium storage material to store and deliver deuterium fuel into fusion reactors, due to its large deuterium storage capacity, low deuterium desorption pressure and fast deuterium absorption kinetics. But it often cracks after deuterium absorption. In this study, the microstructure and deuterium absorption kinetic of β-Zr in various deuteriding conditions (pressure, time and temperature) were investigated. The results showed that, with the increase of deuteriding pressures from 1 bar to 3 bar at 1173 K, the deuteride content and the deuteride morphology changed significantly. During deuterium absorption at 3 bar, the surface deuteride layer was formed first, and then the inner deuteride network was gradually developed with the time. There existed an apparent deuterium concentration gradient from surface to center. With the increase of deuteriding temperatures from 973 K to 1173 K, the deuteride content decreased. The kinetic of deuterium absorption at 1173 K was found to be affected by the deuteriding pressures. Transmission electron microscopy (TEM) results showed that ε deuterides nucleated and grew at the interface of δ deuterides, and small bands with different crystal orientation were found within the ε deuterides. The γ deuterides were found at 3 bar, within which twins and tweed structure were observed. An orientation relationship of <011>δ//<011>ε, {111}δ//{111}ε between δ and ε deuterides was also determined by TEM analysis.

•Deuterium absorption properties and cracking behaviors in Zr–xCu (x = 0 wt.%, 5 wt.%, 10 wt.%) are studied.•Deuterium absorption–desorption cyclic properties in Zr–xCu alloys are investigated.•Deuterium absorption mechanisms in Zr–xCu alloys are determined.•The PCT curves of Zr–xCu alloys are obtained at 900 °C and 800 °C.Zirconium is a kind of deuterium absorption materials and can be used as a candidate deuterium carrier in the nuclear fusion industry. However, it usually cracks after deuterium absorption and fails in its application. For the prevention of cracks, copper particles with good ductility were added into the zirconium by spark plasma sintering (SPS) synthesis method. The results showed that the addition of the Cu element affected the cracking behavior of Zr–xCu alloys significantly. With the addition of the 5%Cu no cracking was observed, and an addition of the 10%Cu lead to an observation of a few large cracks within the second phase, compared in size to the small cracks that appeared in Zr. Moreover, the addition of the Cu element decreased the deuterium absorption capacity of the Zr–xCu alloys and changed the deuterium absorption mechanism from three-dimension diffusion in the Zr alloy to chemical reaction in the Zr–10%Cu alloy. The pressure–composition–temperature (PCT) curves showed that all the Zr alloys had two plateau pressures at 900 °C, and the addition of Cu had an effect on the plateau pressure. After 10 cycles of deuterium absorption–desorption, Zr–5%Cu sample kept a integrity morphology with no cracking at low magnification, on the contrary Zr–10%Cu sample broken into pieces, though both of them kept a higher relative deuterium absorption capacity than that of Zr.

•Decreasing deuterium absorption temperature will increase cracking in Zircaloy-4.•Increasing of deuterium absorption pressure will increase cracking in Zircaloy-4.•Increasing interrupted temperature will increase cracking in Zircaloy-4.•The mechanism on cracking in deuterium absorption Zircaloy-4 is discussed.Zirconium is a kind of deuterium absorption material and can be used as a deuterium carrier in the nuclear industry. However, zirconium usually cracks after deuterium absorption and therefore fails in its application. In this paper, the effects of deuterium absorption temperature, deuterium absorption pressure and interrupted cooling on the cracking of deuterium absorption Zircaloy-4 alloys have been investigated. The results show that as the deuterium absorption temperature decreases from 900 °C to 800 °C or 700 °C, the deuterium absorption amounts and their tendency to crack increase. And with the increase of deuterium absorption pressure, the deuteride types change from δ-ZrD1.66 to ε-ZrD1.8, which is believed to be the key factor in the cracking. Furthermore, the interrupted cooling also has a significant effect on the deuterium absorption cracking. Based on the experimental results, an explanation of why Zircaloy-4 alloy cracks after deuterium absorption is proposed.

The hydrogen absorption cracking behavior of Zr-4 has been investigated based on the microstructure, hydrogen absorption amount as well as residual stress. The results show that the grain size has a pronounced effect on the hydrogen absorption cracking, with the increase of grain size from 30 μm to 500 μm, the cracks vary from small cracks of independence to large cracks that connect with each other along the radial direction. The unsaturated hydrogen absorption samples which consist of γ- and δ-hydrides present a crack-free surface while the saturated hydrogen absorption samples which consist of ɛ-hydride exhibit not only large cracks but also bulges on the surface. The hydride decomposition temperatures of ɛ → δ and δ → α during dehydriding are determined to be about 600 °C and 700 °C respectively. In the unsaturated hydrogen absorption samples, both the thickness expansion and radial residual stress present a positive liner correlation with the hydrogen absorption amount. Based on the experimental results a mechanism of hydrogen absorption cracking is proposed in zirconium alloys.Highlights► The grain size has a pronounced effect on hydrogen absorption cracking. ► Hydrogen absorption amount has a decisive effect on hydrogen absorption cracking. ► Hydrides in saturated/unsaturated hydrogen samples were analyzed by TEM/HRTEM. ► The decomposition temperatures of ɛ → δ and δ → α are about 600 °C and 700 °C respectively. ► The expansions of δ- and ɛ-hydrides during hydrogen absorption were evaluated.

The purpose of this paper is to estimate the fatigue crack growth threshold of a high-Nb TiAl alloy at the different temperatures based on scanning electron microscopy (SEM) in-situ observation. The results indicated that the fatigue crack growth threshold ΔKth of a nearly lamellar high-Nb TiAl alloy with 8% Nb content at room temperature and 750°C was determined as 12.89 MPa·m1/2 and 8.69 MPa·m1/2, respectively. The effect of the elevated temperature on the fatigue crack growth threshold cannot be ignored. At the same time, the early stage of fatigue crack propagation exhibited multicrack initiation and bridge-link behavior.

The microstructures and hydrogen storage properties of as-cast and rapidly solidified V35Ti25Cr40 alloys have been investigated in this paper. The results showed that the rapid solidification refined the dendritic microstructure and altered the element distribution of the alloy. And through the positron annihilation measurements of the vacancy trapping rate (Kd1) and vacancy-trapped positron annihilation lifetime (τ2), it was found that the rapid solidification increased the vacancy concentration and at the same time decreased the vacancy size in the alloy. The XRD results showed that the rapid solidification also significantly enlarged the alloy's lattice parameter. As a result of the microstructure change, the hydrogen absorption capacity and hydrogen absorption rate were increased; and the kinetic mechanism of hydrogen absorption was changed from 3-D diffusion control in the as-cast alloy to chemical reaction control in the rapidly solidified alloy; but the activation property was to some extent weakened after the rapid solidification.

Spark plasma sintering (SPS) is a newly developed technique for multiple-phase material preparation. In this article, a Laves phase related BCC solid solution V–Ti–Cr alloy was prepared by SPS method, and its microstructure and hydrogen storage properties were investigated and compared with those of the alloy prepared by arc melting method. The results indicated that the alloy prepared by SPS method possessed not only excellent activation and kinetics properties, but also a much larger hydrogen storage capacity. The maximum hydrogen storage capacity was determined to be 2.89 mass%, which is about 24% higher than that of the arc melting alloy, and the hydrogen desorption ratio was improved from 35% for the arc melting alloy to 60% for the SPS alloy. This was due to the absence of Laves formation elements in the BCC solid solution and the formation of the interface phase between the Laves phase and the BCC solid solution during the SPS process, which fully optimized the hydrogen storage property of the Laves phase related BCC solid solution alloy.

•Magnesium nanowires are successfully prepared by the physical vapor deposition method.•A distribution map of magnesium nanowires is set up based on our experimental results.•A criterion of the supersaturation of magnesium vapors is proposed to explain formation of magnesium nanowires.•The influence factors on the formation of Mg nanowires have been systematically investigated.Magnesium nanowires were successfully prepared by a physical vapor deposition method, and influence factors on the formation of magnesium nanowires were discussed based on the evaporation/deposition temperature, vacuum level, magnesium vapor concentration and deposition time. The results show that the formation of magnesium nanowires occurs within a specific evaporation/deposition temperature range. Magnesium nanowires become thicker and longer and finally convert into magnesium micronparticles with the increase of evaporation temperature or decrease of deposition temperature. The vacuum level also plays a decisive role in the formation of magnesium nanowires that magnesium nanowires can only be prepared in a high vacuum level. The magnesium vapor concentration and deposition time also have significant influences on the formation of magnesium nanowires. A distribution map of magnesium nanowire is set up based on our experimental results and a criterion of supersaturation of magnesium vapors is proposed in the explanation of the formation of magnesium nanowires.