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The alloying effect of Zr on β (body-centred cubic)-phase stability was investigated in α (hexagonal close packed)-type Ti–Al alloys. According to calculations and experiments, adding Zr significantly modified the β-phase stability, because Zr was identified as a β-stabilising element in these Ti–Zr–Al alloys under the solution treatment. However, the water-quenched β-phase did not continue to be preserved after aging. In addition, stress-induced α″ (orthorhombic)-phase martensite transformation would occur during deformation. [ABSTRACT FROM AUTHOR]

A series of Zr 50 –Ti 50 (at%) alloy specimens with different treatments was prepared. Tensile test, X-ray diffraction (XRD), optical microstructure, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses were performed to investigate alloy tensile properties and microstructure. Hot-rolling process was found to have a remarkable strengthening effect. The tensile strength of hot-rolled specimens had an increase of 37% compared with solution-treated specimen (undeformed). All specimens exhibited α ′-Zr structures and similar microstructures. However, a significant plasticity difference was observed in the Zr 50 –Ti 50 hot-rolled specimens with different cooling rates. Detailed TEM microstructural analysis showed that the morphology of twins in the hot-rolled specimens was different. Most of the twins were nano-twins. It was found that the twins had effective on Zr 50 –Ti 50 alloy plasticity, in the meantime significant effects on tensile properties due to the complicated interactions between twin boundaries and dislocations. All these findings in this work may provide a new strengthening mechanism for Zirconium-based alloys. [ABSTRACT FROM AUTHOR]

The effects of beryllium (Be) addition on the microstructure and mechanical properties of hot-rolled Zr–3Al– χ Be alloys ( χ =0, 0.4, 0.6, and 0.8 wt%) were characterized experimentally. X-ray diffraction and optical microscopic results indicated that the complete α phase was replaced by α phase+Be 2 Zr compound in the alloys after Be addition. Meanwhile, with an increase of Be content from 0.4 wt% to 0.8 wt%, the content of Be 2 Zr particles increased in the examined Zr–3Al– χ Be alloys. Moreover, partial α recrystallization was observed in the hot-rolled Zr–3Al alloy. The degree of α recrystallization tended to increase in the alloys with Be addition. Adding Be is beneficial to the improvement of the tensile properties. The Zr–3Al–0.8Be alloy exhibited maximum ultimate tensile strength of 1103 MPa, which increased by 27% compared with that of the hot-rolled Zr–3Al alloy and the elongation remained at 6.07%. Fractography results indicated that the fracture modes of the Zr–3Al– χ Be alloys transformed from ductile to a combination of ductile and brittle with the gradual addition of Be. [ABSTRACT FROM AUTHOR]

Novel ZrB 2 -reinforced zirconium (Zr) alloys with different boron (B) and aluminum (Al) contents were produced by arc-melting technique. Microstructural observation indicated that both the α-lath and the prior-β grain size were significantly refined with increased B content. The thickness of α lath gradually increased with increased solute atom Al content. Compressive test results showed that the modulus and strengths of the alloys improved with increased ZrB 2 and Al contents. The presence of abundant ZrB 2 whiskers and solid solution atom Al were responsible for the increased Young׳s modulus. The strengthening mechanisms can be attributed to strengthening through load transfer between the ZrB 2 whiskers and Zr matrix, morphological changes in alloys resulting from the formation of ZrB 2 whiskers, and solid-solution strengthening caused by Al addition. Fractography confirmed that ZrB 2 whiskers undertook the load transferred from Zr matrix and that crack sources were primarily generated at ZrB 2 whiskers. [ABSTRACT FROM AUTHOR]

In the present study, the effects of Be content on the microstructure and mechanical properties of hot rolled ZrBe binary alloys were investigated. Microstructures, i.e. the phases present in the alloys, were characterized using X-ray diffraction (XRD), optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). At the same processing temperature, the volume fraction of α׳ martensite and Be 2 Zr compound gradually increases but the volume fraction of α phase decreases with increasing Be content. This can be attributed to the low solubility of Be in Zr alloys and the decrease of α to β phase transition temperature. Simultaneously, the average Be 2 Zr particles size shows an increasing trend with adding Be content. With increasing Be content, the tensile strength increases but ductility decreases. The alloy with 1.0 wt% Be possessed highest ultimate tensile strength (892 MPa) with an elongation of 7.06%. The strengthening and toughening mechanisms of hot-rolled ZrBe alloys were also discussed. [ABSTRACT FROM AUTHOR]

The microstructure, mechanical property behavior, and fracture characteristics of Zr– χ B alloys ( χ =0, 0.05, 0.3, 0.8 wt%) obtained by casting and hot-rolling were investigated. Microstructural observation indicated that the dendritic equiaxed prior-β grain morphology was slightly elongated after hot-rolling treatment. The widths of the α lath of all the hot-rolled Zr– χ B alloys were similar, and the length of the α lath decreased with increasing boron concentration. Tensile test results showed that the improved strength of the Zr– χ B alloys can be primarily attributed to grain refinement. Strengthening the Zr– χ B alloys could also be achieved by a shear-lag model mechanism because of the high strength and modulus of the ZrB 2 whiskers. The refinement of the α lath and the presence of the ZrB 2 whiskers were responsible for the reduced elongation-to-failure. Fractography indicated that fracture behavior strongly depends on the orientation of the ZrB 2 whiskers. The effect of this orientation on the fracture mechanisms of the ZrB 2 whiskers and the Zr– χ B alloys was also discussed. [ABSTRACT FROM AUTHOR]

The Zr345Ti35Al33V alloy having good mechanical properties is a potential structural material to apply in the aerospace industry. The microstructure and mechanical properties of Zr345Ti35Al33V alloy during annealing heat treatment were investigated. The specimens annealed from 500 to 800°C are composed of α and β two phases. No compound is detected in specimens annealed in that temperature range. The microstructure of annealed specimens is characterized as a typical basketweave microstructure. Two microstructural parameters, thickness of plate α phase and relative fraction of β phase, were measured in specimens annealed at various temperatures. The thickness of plate α phase and the relative fraction of β phase increase with the increasing annealing temperature while the specimens anneal from 500 to 700°C. However, a decreased phenomenon of those microstructural parameters occurs while the specimen anneals at 800°C. The strength of examined alloy increases from 1306 to 1370MPa for tensile strength and from 1116 to 1277MPa for yield strength, inversely, the elongation decreases from 9.5% to 5.8% with the increasing thickness of plate α phase and fraction of β phase in specimens annealed in the range from 500 to 800°C. [ABSTRACT FROM AUTHOR]

Abstract: The 30Zr–62Ti–5Al–3V (wt%) alloy with ultra-high strength and good ductility was prepared via consumable electro-arc melting, forging, and heat treatment. The phase transition and structure evolution of the alloy during heat treatment were also investigated. X-ray diffraction (XRD) results show an orthorhombic martensite α′′ phase in the specimen solution-treated at 825°C. The orthorhombic martensite α′′ phase decomposed into α and β phases during the subsequent ageing treatment. No intermetallic compound peak was found in the XRD patterns of the specimens under different conditions. Microstructural analysis shows that the fine short-bar-shaped α phase precipitated along the original β grain boundary together with the ultrafine dot-shaped α phase that presented inside the original β grain when the ageing temperature was lower than 550°C. As the ageing temperature increased, the dot-shaped α phase inside the original β grain gradually grew into the short-bar shape. The different microstructures resulted in varied mechanical properties. After ageing at 500°C, the tensile strength reached 1622MPa; at the same time, the 2.1% ductility in terms of elongation was retained. As the ageing temperature increased to 650°C, the ductility (in terms of elongation) increased to 9.3% and the strength remained above 1400MPa. The ultra-high strength and good ductility of the studied alloy make it a good candidate for a wide range of applications. [Copyright &y& Elsevier]