Abstract
Beta (β) Ti-alloys are promising class of Ti-alloys for high performance structural applications, thanks to their high strength to weight ratios and outstanding corrosion resistance. In the current work, Ti-4.5Fe-7Cr low cost beta Ti-alloy was produced by investment casting. DSC test was carried out to determine the transformation temperatures. The influence of solution treatment and aging temperatures on microstructure and mechanical properties were studied. Six heat treatment cycles were carried out, two solution treatment cycles in β- and α+β-range at 900 °C and 750 °C, respectively, and four precipitation hardening cycles, i.e. α+β-aging at 450 °C and 650 °C after solution treating at both 900 °C and 750 °C. Microstructure examination, XRD analysis and compression test had been conducted to investigate the influence of the different heat treatment regimes on the proposed alloy. Solution treatment at 900 °C results in coarser β-grain size than at 750 °C; hence lower strength. Strengthening by α-phase precipitation and grain refinement was achieved during aging. Aging at 650 °C results in higher strength than at 450 °C although coarser grain size, this is attributed to stronger effect of precipitation hardening of α-phase at 650 °C as a result of its higher amount than at 450 °C. The designed alloy shows high strength and excellent malleability, i.e. the alloy reveals superior plastic deformability, where specimens did not reveal any fracture; and the compression tests were interrupted at a compressive strain of 33%; therefore, this alloy may find applications as a healthcare, automotive or aerospace material.
Highlights
In spite of the outstanding properties of titanium alloys, its high cost limits the widespread utilization in industry [1,2,3,4]
The transformation ends on heating at 870 °C. These three temperatures are indicated on the heating curve (Fig. 3) by BH, PH and EH for beginning, peak and end of α to βtransformation on heating, respectively
The current results reveal that average grain size after aging is finer than after solution treatment
Summary
In spite of the outstanding properties of titanium alloys, its high cost limits the widespread utilization in industry [1,2,3,4]. This high cost of titanium alloys includes the high price of the raw materials plus the cost of production. Titanium requires vacuum casting followed by deformation using any metal forming technique aiming at enhancing the alloy properties as possible to promote its performance in the application. Investment casting may be followed by heat treatment for more enhancement of the properties. Short holding time heat treatment can be conducted to reduce the total production cost
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