α′ Type Ti–Nb–Zr alloys with ultra-low Young's modulus and high strength

Abstractα′ phase based Ti–Nb–Zr alloys with low Young's modulus and high strength were prepared, and their microstructure and mechanical properties were characterized. It was revealed that the lattice expansion by Nb and Zr addition as well as the presence of a few of α″ martensite might be responsible for the low modulus achieved. Ti–15Nb–9Zr alloy, with ultralow modulus of 39GPa and high strength of 850MPa, could be a potential candidate for biomedical applications

Assisting in Auditing of Buffer Overflow Vulnerabilities via Machine Learning

Buffer overflow vulnerability is a kind of consequence in which programmers’ intentions are not implemented correctly. In this paper, a static analysis method based on machine learning is proposed to assist in auditing buffer overflow vulnerabilities. First, an extended code property graph is constructed from the source code to extract seven kinds of static attributes, which are used to describe buffer properties. After embedding these attributes into a vector space, five frequently used machine learning algorithms are employed to classify the functions into suspicious vulnerable functions and secure ones. The five classifiers reached an average recall of 83.5%, average true negative rate of 85.9%, a best recall of 96.6%, and a best true negative rate of 91.4%. Due to the imbalance of the training samples, the average precision of the classifiers is 68.9% and the average F1 score is 75.2%. When the classifiers were applied to a new program, our method could reduce the false positive to 1/12 compared to Flawfinder

Microstructural evolution and mechanical behavior of metastable β-type Ti–30Nb–1Mo–4Sn alloy with low modulus and high strength

A metastable β-type Ti–30Nb–1Mo–4Sn alloy with ultralow elastic modulus and high strength was fabricated. Under the solution treatment state, the Ti–30Nb–1Mo–4Sn alloy possesses low yield strength of about 130 MPa owing to the presence of the coarse α′′ martensitic laths. Upon a cold rolling and annealing process, the martensitic transformation from β to α′′ is significantly retarded due to the inhibitory effect of grain boundaries and dislocations. As a result, the metastable β phase with low total amount of β-stabilizers is retained to room temperature, giving rise to a low modulus of 45 GPa. Meanwhile, nano-sized α precipitates and dislocation tangles play a key role in strengthening the Ti–30Nb–1Mo–4Sn alloy, resulting in a high tensile strength of ~1000 MPa. With low elastic modulus and high strength, the metastable β-type Ti–30Nb–1Mo–4Sn alloy could be a potential candidate for biomedical materials

A β-type TiNbZr alloy with low modulus and high strength for biomedical applications

The effect of thermo-mechanical treatment on the mechanical properties of a novel β-type Ti–36Nb–5Zr (wt%) alloy has been investigated. The solution treated alloy consists of β and α″ phases and exhibits a two-stage yielding with a low yield stress (around 100 MPa). After cold rolling at a reduction of 87.5% and subsequent annealing treatment at 698 K for 25 min, a fine microstructure with nanosized α precipitates distributed in small β grains as well as high density of dislocations was obtained to achieve a yield strength of 720 MPa and a ultimate tensile strength of 860 MPa. In spite of the formation of α precipitates, the β-stabilizers are not enriched in the parent β matrix due to the short duration and low temperature of the thermal treatment, resulting in a low chemical stability of β phase. The low stability of β phase and the small volume fraction of α precipitates produce a low Young׳s modulus of 48 GPa. Such an excellent combination of low elastic modulus and high strength in mechanical properties indicates great potential for biomedical applications

Effect of thermo-mechanical treatment on mechanical and elastic properties of Ti–36Nb–5Zr alloy

The evolutions of phase constitutions and mechanical properties of a β-phaseTi–36Nb–5Zr (wt%) alloy during thermo-mechanical treatment were investigated. The alloy consisted of dual (β+α″) phase and exhibited a double yielding phenomenon in solution treated state. After cold rolling and subsequent annealing at 698 K for 20 min, an excellent combination of high strength (833 MPa) and low modulus (46 GPa) was obtained. The high strength can be attributed to high density of dislocations, nanosized α phase and grain refinement. On the other hand, the low Young׳s modulus originates from the suppression of chemical stabilization of β phase during annealing, which guarantees the low β-phase stability. Furthermore, the single-crystal elastic constants of the annealed Ti–36Nb–5Zr alloy were extracted from polycrystalline alloy using an in-situ synchrotron X-ray technique. The results indicated that the low shear modulus C44 contributes to the low Young׳s modulus for the Ti–36Nb–5Zr alloy, suggesting that reducing C44 through thermo-mechanical treatment might be an efficient approach to realize low Young׳s modulus in β-phase Ti alloys. The results achieved in this study could be helpful to elucidate the origin of low modulus and sheds light on developing novel biomedical Ti alloys with both low modulus and high strength

Effect of Silicon on the Microstructure and Performance of the New Binary Deep Eutectic Ti–Cu–Zr–Ni-Based Filler Metal

This study designed (Ti0.55Cu0.20Zr0.15Ni0.10)1−xSix amorphous alloys based on binary deep eutectics and examined the effect of silicon (Si) on the amorphous forming ability of the filler alloys. The results show that a certain amount of Si added to the filler metals could improve the amorphous forming ability of the alloys. Under the same experimental conditions, the Ti0.55Cu0.20Zr0.15Ni0.10 filler metal with 0.5 wt % Si had the strongest amorphous forming ability compared to the other filler alloys containing different amounts of Si; its reduced glass transition temperature (Trg) was 0.5554, and its supercooled liquid phase region width (∆Tx) reached 60 °C. The (Ti0.55Cu0.20Zr0.15Ni0.10)99.5%Si0.5% filler metal designed in these experiments presented good amorphous forming ability and wettability. The brazed joint of SiC and TC4 obtained with this amorphous filler metal showed a shear strength of 102 MPa, indicating an increase of 122% compared to the brazed joint obtained with the filler metal without Si

The relationship between protocol states and program paths program paths.

<p>The relationship between protocol states and program paths program paths.</p

An example of crossover operator.

<p>An example of crossover operator.</p

A model-guided symbolic execution approach for network protocol implementations and vulnerability detection

<div><p>Formal techniques have been devoted to analyzing whether network protocol specifications violate security policies; however, these methods cannot detect vulnerabilities in the implementations of the network protocols themselves. Symbolic execution can be used to analyze the paths of the network protocol implementations, but for stateful network protocols, it is difficult to reach the deep states of the protocol. This paper proposes a novel model-guided approach to detect vulnerabilities in network protocol implementations. Our method first abstracts a finite state machine (FSM) model, then utilizes the model to guide the symbolic execution. This approach achieves high coverage of both the code and the protocol states. The proposed method is implemented and applied to test numerous real-world network protocol implementations. The experimental results indicate that the proposed method is more effective than traditional fuzzing methods such as SPIKE at detecting vulnerabilities in the deep states of network protocol implementations.</p></div