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To enhance the mechanical properties (i.e. strength and elongation) of the face-centered cubic (fcc) α-phase in the Au-Cu-Al system, this study focused on the introduction of the martensite phase (doubled B19 (DB19) crystal structure of Au2CuAl) via the manipulation of alloy compositions. Fundamental evaluations, such as microstructure observations, phase identifications, thermal analysis, tensile behavior examinations, and reflectance analysis have been conducted. The presence of fcc annealing twins was both observed in the optical microscope (OM) and the scanning electron microscope (SEM) images. Both the strength and elongation of the alloys were greatly promoted while the DB19 martensite phase was introduced into the alloys. Amongst all the prepared specimens, the 47Au41Cu12Al and the 44Au44Cu12Al alloys performed the optimized mechanical properties. The enhancement of strength and ductility in these 2 alloys was achieved while the stress plateau was observed during the tensile deformation. A plot of the ultimate tensile strength (UTS) against fracture strain was constructed to illustrate the effects of the introduction of the DB19 martensite phase on the mechanical properties of the alloys. Regardless of the manipulation of the alloy compositions and the introduction of the DB19 martensite phase, the reflectance stayed almost identical to pure Au.

In view of the exponential rate of advancement in robotics technology, a composite material, which is promising for high-speed and large-strain actuation and sensing applications, has been developed in this study. Single-crystalline Ni49.9Mn28.5Ga21.6 (SC Ni-Mn-Ga) ferromagnetic shape memory alloy particles were fabricated from the polycrystalline Ni-Mn-Ga alloy by a well-controlled mechanical crushing. X-ray diffractions revealed a mixture of 5M- and 7M-martensitic phases in the SC Ni-Mn-Ga particles. A composite consisting of the silicone rubber and 20 vol.% of the crystallographically and spatially oriented SC Ni-Mn-Ga particles was fabricated by curing under a magnetic field and the chain-oriented structure was confirmed by a micro-computed tomography. This composite, which exhibited a magnetic field induced rubber-like behavior with a magnetostrain as high as 4.0% despite reduced filling factor, was attributed to the co-existence of the 5M- and 7M-martensitic phases.

The Au–Cu–Al biocompatible shape memory alloys (SMAs) have attracted much attention due to the requirements of biomedical applications. However, brittleness remains a critical issue in the intermetallics of Au–Cu–Al alloys. In this study, to solve the dilemma of embrittlement, Ag was introduced into the Au–Cu–Al alloy to realize the ductile phase toughening (DPT) since the ductile disordered–fcc phase was predicted to precipitate in the brittle parent β phase based on the Ag–Au–Cu phase diagram. Microstructure observations, chemical composition analysis, crystal structure identifications, and thermal analysis revealed that the Au–28Cu–16Al–28Ag (mol.%) alloy was mainly composed of the Ag–rich α1 primary solidification phase with disordered–fcc structure and the eutectic structure of the α1 phase and the β phase with L21 structure. The ductile phase was successfully inserted into the brittle Au–Cu–Al intermetallic while the martensitic transformation temperature and crystal structures remained almost uninterrupted. In the cyclic loading–unloading tensile tests, the alloy mainly composed of the β phase failed in the early elastic region due to its embrittlement; while the alloy mainly composed of the α1 phase performed 29% in the total strain deformation. The Au–28Cu–16Al–28Ag alloy, which is composed of the β phase and the α1 phase, solve the issue of embrittlement; in addition, shape recovery was also found in this alloy during unloading. According to the microstructure observations, cyclic tensile tests, and fracture surface observations, the aforementioned improvement of strengthening and enhancement of ductility were brought from the insertion of the ductile α1 phase into the brittle β/β grain boundaries.

Owing to the world population aging, biomedical materials, such as shape memory alloys (SMAs) have attracted much attention. The biocompatible Ti–Au–Ta SMAs, which also possess high X–ray contrast for the applications like guidewire utilized in surgery, were studied in this work. The alloys were successfully prepared by physical metallurgy techniques and the phase constituents, microstructures, chemical compositions, shape memory effect (SME), and superelasticity (SE) of the Ti–Au–Ta SMAs were also examined. The functionalities, such as SME, were revealed by the introduction of the third element Ta, in addition, obvious improvements of the alloy performances of the ternary Ti–Au–Ta alloys were confirmed while compared with that of the binary Ti–Au alloy. The Ti3Au intermetallic compound was both found crystallographically and metallographically in the Ti–4 at.% Au–30 at.% Ta alloy. The strength of the alloy was promoted by the precipitates of the Ti3Au intermetallic compound. The effects of the Ti3Au precipitates on the mechanical properties, SME, and SE were also investigated in this work. Slight shape recovery was found in the Ti–4 at.% Au–20 at.% Ta alloy during unloading of an externally applied stress.

The effects of the Cr and Sn addition concentrations on the cold–workability, phase constituents, mechanical properties, shape memory effect (SME), and superelasticity were investigated. A systematic screening of the β–Ti alloy, which was slight–alloyed by Cr and Sn, was executed in this work. Cold–workability of the Ti–Cr–Sn alloys was greatly promoted along with the increasing concentration of Cr and Sn. The parent β–phase was successfully stabilized at room temperature merely by the slight introduction of Cr and Sn β–stabilizers. Perfect SME of 100% recovery rate was realized in the Ti–5.5Cr–3Sn alloy and the shape recovery rate performed a good inclination with the overall Cr + Sn addition concentration in the bending tests. Obvious two–stage yielding, which inferred the stress–induced martensitic transformation (SIMT) and/or martensite variant reorientation (MVR) before yielding, was observed in the tensile tests. The two–stage yielding also explained the SME well. The excellent elongation of 40% and 45%, which were found in the Ti–6.0Cr–3Sn and the Ti–6.0Cr–2Sn alloys, was explained by the {332} mechanical twinning. Slight pseudoelasticity was also found in most of the specimens. Functional mappings of the Ti–Cr–Sn alloys, which could be powerful tools for future investigations, have been constructed in this study. The Ti–6.0Cr–3Sn alloy, which possessed high ultimate tensile strength, excellent ductility of 40%, outstanding SME of 91.0%, and good shape recovery after removing the external stress, could be a promising material for the applications in biomedical materials.

The effects of Cr and Sn additives on the phase constitution, lattice deformation strain, transformation temperature, and deformation behavior of Ti-Cr-Sn alloys were systematically investigated to inform the development of a superelastic alloy with high lattice deformation strain. The addition of Cr and Sn changes the reverse martensitic transformation temperature by −190 K/mol% Cr and −141 K/mol% Sn, respectively. The lattice deformation strains (η1, η2, and η3) were evaluated in terms of the lattice parameters of the parent β phase to the martensite α″ phases. In addition, the composition range of the alloys that are expected to exhibit superelasticity and high deformation strain near the human body temperature was established based on the composition dependence of lattice deformation strain and transformation temperature. The deformation behavior of Ti-Cr-Sn alloys at room temperature changes from the shape memory effect to superelasticity with increasing Cr and Sn contents. In particular, Ti-2.5Cr-8.5Sn, Ti-3.0Cr-7.5Sn, Ti-3.0Cr-8.0Sn, Ti-3.5Cr-7.0Sn, and Ti-4.0Cr-6.5Sn alloys exhibit superelasticity at room temperature and a high lattice deformation strain (η2) that exceeds 6.32%. It is concluded that Cr and Sn are more effective than other β-stabilizing elements at lowering the martensitic transformation temperature of β-Ti shape memory alloys without reducing the lattice deformation strain.

A series study of the ternary near–eutectoid Ti–Au–Cr shape memory alloys (SMA) at the Ti–rich corner was explored in this work towards the applications of biomedical materials. Fundamental analysis, such as microstructures, phase constitutions, lattice parameters, and mechanical properties of the specimens, were examined along with their functional properties, such as shape memory effect (SME) and superelasticity (SE). Most of the alloys possess good cold–workability except for those with great amounts of precipitates of the brittle Ti3Au at the high Au addition specimens. The Ti–4Au–8Cr alloy excelled in strength while the Ti–2Au–8Cr alloy surpassed other alloys in ductility. Most of the specimens possess SME as well as pseudoelasticity and/or superelasticity indicating the functionality of the Ti–Au–Cr alloys towards biomedical applications. The discrimination between the α′–martensite phase and the α′′–martensite phase was conducted by the TEM observation. The α′–martensite phase, which unexpectedly performed SME in this study was determined to locate exactly at the boundary of the α′–martensite regime and the α′′–martensite regime. The SME of the alloys, which were composed of the α′–martensite phase, were thus deduced to originate from the similarity of the α′–martensite and the α′′–martensite.

Influences of the Fe addition in various concentrations on the near–eutectoid Ti–4Au alloys were systematically investigated in this study in consideration of the great number of requirements for the biomedical materials. The Ti–4Au–xFe (x = 1, 3, 4, 5, 6, and 7 at.%) alloys were synthesized by physical metallurgy and their microstructures, crystal structures, lattice parameters, phases, and mechanical properties were analyzed. In addition, the investigations for the shape memory effect (SME) and superelasticity (SE) were also conducted to examine their performances of functionality. The β–phase was stabilized at room temperature by the 3 at.% addition of Fe into the binary Ti–4Au alloy. The specimen with optimized mechanical properties by trading–off its strength and ductility was found in the Ti–4Au–4Fe alloy. SME was revealed clearly in the Ti–4Au–3Fe alloy and slightly in the Ti–4Au–4Fe alloy; while SE was observed in the Ti–4Au–4Fe alloy. It was observed that there was a growing trend of the Ti3Au precipitate amount with the raised concentration of Fe addition. The precipitates of the Ti3Au were fine–tuned by the Fe addition for tailoring the various mechanical properties of the ternary Ti–4Au–xFe alloys, and the balanced performance was achieved by the 4 at.% Fe addition.

In this paper, a feedrate scheduling algorithm based on master axis is proposed to generate smooth five-axis tool center point (TCP) trajectory. The method first plans corner feedrate while respecting jerk continuity of three linear axes at block corner. The axis with the maximum movement among TCP and rotary axes is selected to be a master, and the ratios among the movements of the master and other axes are obtained. Five-axis feedrate regulation formulation (FFRF) is utilized to evaluate the velocity of the master axis. Feedrate command on TCP is adjusted with the constraints of jerks and movements of TCP and rotary axes. S-shape acceleration/ deceleration (ACC/DE C) method is us ed to achieve velocity smoothing and generate five-axis interpolation commands. Finally, the cutting experiments are performed to verify the efficiency of the proposed technology on a five-axis engraving machine.

In this paper, a novel tool center point (TCP) interpolation method is proposed to generate smooth feedrate and tool trajectory for five-axis machining. TCP interpolator consists of two processes: block and look-ahead process. The block process determines the maximum feedrate of each block based on five-axis velocity equations, the movements of TCP and rotary axes. It detects sharp corners among NC blocks, and inserts arc segments into blocks with sharp corners to avoid tangential discontinuities. Corner feedrate is determined based on contour tolerance and kinematic constraints where velocity, acceleration and jerk on TCP and five-axis are all taken into consideration. The velocity profile of the TCP on each block is planned in the look-ahead process by means of TCP movement, corner velocity, velocity commands and jerk limits. Finally, simulations and experiments are carried out to validate the efficiency of the proposed method in improvement of the contour accuracy for five-axis machining.