رفتار خزشی آلیاژ آلومینیوم - تیتانیوم

Creep behavior of Ti-6Al-4V from 450°C to 600°C

رفتار خزشی Ti-6Al-4V از 450  تا 600 درجه سانتیگراد

ABSTRACT

We present in this paper the creep behavior of Ti-6Al-4V from 450°C to 600°C under applied stress from 100 MPa to 500 MPa. Creep behavior is studied analyzing creep damage after tests and calculating stress exponent (n) and activation energy (Q). Operating creep deformation mechanisms characterization is possible by analyzing crept microstructure by TEM. A comparison of n and Q values with values from literature and a correlation with TEM micrographs will lead us to a discussion about operating creep deformation mechanisms.

 

ریزساختار و خواص مکانیکی آلیاژ تیتانیوم پس از عملیات حرارتی

Microstructure and mechanical properties of 

TC21 titanium alloy after heat treatment 

ریزساختار و خواص مکانیکی آلیاژ تیتانیوم TC21 پس از عملیات حرارتی

ABSTRACT

Microstructure evolutions during different heat treatments and influence of microstructure on mechanical properties of TC21 titanium alloy were investigated. The results indicate that the excellent mechanical properties can be obtained by adopting air cooling after forging followed by heat treatment of (900 °C, 1 h, AC)+(590 °C, 4 h, AC). Deformation in single β field produces pan-like prior β grains, while annealing in single β field produces equiaxed prior β grains. Cooling rate after forging or annealing in single β field and the subsequent annealing on the top of α+β field determine the content and morphology of coarse α plates. During aging or the third annealing, fine secondary α plates precipitate. Both ultimate strength and yield strength decrease with the content increase of coarse α plates. Decreasing effective slip length and high crack propagation resistance increase the plasticity. The crisscross coarse α plates with large thickness are helpful to enhance the fracture toughness.

 

رفتار قالب پرکنندگی مذاب های تیتانیوم Mold-filling behavior of titanium melts in vertically rotating molds

Effect of centrifugal and Coriolis forces on

the mold-filling behavior of titanium melts in vertically rotating molds

اثرات نیروهای گریز از مرکز و نیروهای کوریولیس بر رفتار قالب پرکنندگی مذاب های تیتانیوم

در قالب هایی که به صورت عمودی می چرخند

ABSTRACT

The vertical centrifugal-casting technique is widely used in the manufacture of various irregularly-shaped castings of advanced structural alloys with thin walls, complex shapes and/or large sizes. These castings are used in the increasing applications in aero-space/aviation industries, human teeth/bone repairs with near-net shaped components, etc. In a vertically rotating casting system, the mold-filling processes of alloy melts, coupled with solidification-heat transfer, may be much more complicated, because they are driven simultaneously by gravity, centrifugal and Coriolis forces. In the present work, an N-S/VOF-equations-based model, solved using a SOLA-VOF algorithm, under a rotating coordinate system was applied to numerically investigate the impacts of centrifugal and Coriolis forces on metallic melt mold-filling processes in different vertical centrifugal-casting configurations with different mold-rotation rates using an authors' computer-codes system. The computational results show that the Coriolis force may cause remarkable variations in the flow patterns in the casting-part-cavities of a large horizontal-section area and directly connected to the sprue via a short ingate in a vertical centrifugal-casting process. A "turn-back" mold-filling technique, which only takes advantage of the centrifugal force in a transient rotating melt system, has been confirmed to be a rational centrifugal-casting process in order to achieve smooth and layer-by-layer casting-cavities-filling control. The simulated mold-filling processes of Ti-6AI-4V alloy melt, in a vertical centrifugal-casting system with horizontally-connected plate-casting cavities, show reasonable agreement with experimental results from the literature.

 

آلیاژهای Ti-25Nb-xSn ریختگی برای کاربردهای بیوپزشکی

The structure and mechanical properties of

as-cast Ti–25Nb–xSn alloys for biomedical applications

ساختار و خواص مکانیکی آلیاژهای Ti-25Nb-xSn ریختگی برای کاربردهای پزشکی زیستی

ABSTRACT

The effects of tin on the structure and mechanical properties of a Ti–25Nb-based system were studied with an emphasis on improving the strength/modulus ratio. Commercially pure titanium (c.p. Ti) was used as a control. As-cast Ti–25Nb and a series of Ti–25Nb–xSn (x=1, 3, 5, 7, 8, 9, 10, 11, 13, and 15 wt%) alloys prepared using a commercial arc-melting vacuum pressure casting system were investigated. The experimental results showed that the as-cast Ti–25Nb has an α″ phase, and when 1–5 wt% Sn was introduced into the Ti–25Nb alloy, the structure remained essentially unchanged. However, with 7–15 wt% Sn, retention of the metastable β phase began. Among the developed Ti–25Nb–xSn alloys, all the alloys had good ductility, and Ti–25Nb–8Sn and Ti–25Nb–9Sn alloys had lower bending moduli (52 and 53 GPa, respectively) than c.p. Ti (99 GPa) and the other Ti–25Nb-based alloys (61–133 GPa). Moreover, Ti–25Nb–9Sn and Ti–25Nb–11Sn alloys exhibited higher bending strength/modulus ratios, as large as 20.5 and 20.6, respectively, higher than those of c.p. Ti (8.5) and the Ti–25Nb alloys (19.8). The Ti–25Nb–10Sn (41°) and Ti–25Nb–11Sn (46°) alloys had superior elastically recoverable angles, about 17.0 and 15.2 times greater than that of c.p. Ti, respectively. In the current search for a better implant material, β-phase Ti–25Nb-(8–11)Sn alloys show considerable promise due to their low moduli, ductile properties, excellent elastic recovery capability, reasonably high strength (or high strength/modulus ratio), and better shape memory effect

 

ورق های تیتانیوم EBW به عنوان ماده ای برای قطعات کشیده شده

EBW  titanium  sheets  as  material  for  drawn  parts

ورق های تیتانیوم EBW به عنوان ماده ای برای قطعات کشیده شده

ABSTRACT

The growing demand for high strength, lightweight and corrosion-resistant drawn parts has created increasing interest in the use of titanium and its alloys. Additional benefits may result from the use of tailor-welded blanks, allowing for significant savings in material, and the possibility of applying higher strength sheets exactly where needed. When forming welded blanks, it is necessary to overcome many technological barriers which are not reflected in technical literature. Therefore, some prior experience in numerical simulations is needed before embarking on further studies of welded blanks formability. For this purpose, it is necessary to determine the mechanical parameters of the base materials, as well as the fusion and heat-affected zones.

 

آنالیز اشعه ایکس Ti-Nb-Ta-Zr در آلیاژهای تیتانیوم

In situ X-ray analysis of mechanism of nonlinear

super elastic behavior of Ti–Nb–Ta–Zr system beta-type titanium alloy

for biomedical applications

آنالیز اشعه X در جای مکانیسم‌ رفتار سوپرالاستیک غیر‌خطی سیستم Ti-Nb-Ta-Zr

در آلیاژهای تیتانیوم نوع بتا برای کاربردهای زیست‌پزشکی

ABSTRACT

Ti–XNb–10Ta–5Zr (mass %) alloys based on nominal compositions of Ti–35Nb–10Ta–5Zr, Ti–30Nb–10Ta–5Zr, and Ti–25Nb–10Ta–5Zr were fabricated through powder metallurgy and forging and swaging processes for biomedical applications. The tensile deformation mechanisms of the Ti–25Nb–10Ta–5Zr, Ti–30Nb–10Ta–5Zr, and Ti–35Nb–10Ta–5Zr alloys were investigated in situ by X-ray diffraction analysis under several loading conditions.

Under the loading conditions, the X-ray diffraction peaks of all the specimens shifted to higher angles than those obtained under the unloading conditions. For the Ti–30Nb–10Ta–5Zr alloy, the elastic deformation is considered to progress continuously in a different crystal direction although after the elastic strain reaches elastic limit in the crystal direction where the elastic limit is the smallest, slip deformation occurs in that crystal direction. The elastic modulus of this alloy appears to decrease in terms of strain over the proportional limit. Thus, the elastic deformation behavior of the Ti–30Nb–10Ta–5Zr alloy does not obey Hooke's law.

 جهت دانلود رایگان نسخه لاتین این مقاله اینجا کلیک کنید .

 

اثر میکروساختار ماده بر فرسایش ابزار هنگام ماشینکاری آلیاژهای Ti

 Experimental investigation on the effect of the material microstructure on tool wear when machining hard titanium alloys: Ti–6Al–4V and Ti-555

بررسی اثر میکروساختار ماده بر فرسایش ابزار هنگام ماشینکاری آلیاژهای سخت تیتانیوم :  Ti-555; Ti – 6Al – 4V

ABSTRACT

An experimental investigation was conducted in this work to analyze the effect of the workpiece microstructure on tool wear behavior and stability of the cutting process during marching difficult to cut titanium alloys: Ti–6Al–4V and Ti-555. The analysis of tool–chip interface parameters such as friction, temperature rise, tool wear and workpiece microstructure evolution under different cutting conditions have been investigated. As the cutting speed increases, mean cutting forces and temperature show different progressions depending on the considered microstructure. Results show that wear modes of cutting tools used for machining the Ti-555 alloy exhibit contrast from those obtained for machining the Ti–6Al–4V alloy. Because of the fine-sized microstructure of the near-β titanium Ti-555, abrasion mode was often found to be the dominate wear mode for cemented cutting tools. However, adhesion and diffusion modes followed by coating delamination process were found as the main wear modes when machining the usual Ti–6Al–4V alloy by the same cutting tools. Moreover, a deformed layer was detected using SEM–EDS analysis from the sub-surface of the chip with β-grains orientation along the chip flow direction. The analysis of the microstructure confirms the intense deformation of the machined surface and shows a texture modification.