Abstract
Nickel–Titanium (NiTi)-based shape-memory alloys (SMA) are utilized in automotive, biomedical, microsystem applications because of their excellent shape memory effect, biocompatibility and super elastic properties. These alloys are considered difficult to cut—especially with conventional technologies because of the work hardening and residual stresses. Laser-machining is one of the most effective tools for processing of these alloys especially for microsystem applications. In this work, a thorough investigation of effect of process parameters on machining of microchannels in NiTi SMA is presented. In addition, a multi-objective optimization is carried out in order to find the optimal input parameter settings for the desired output performances. The results show that the quality of microchannels is significantly affected by input parameters. Layer thickness was found to have a significant effect on taper angle of the microchannel. Scan speed, layer thickness and scan strategy were found to have significant effects on both spatter thickness and top-width error, but in opposite directions. The multi-objective optimization-minimizing taper angle and spatter thickness revealed an optimal solution that was characterized by high frequency, moderate speed and low layer-thickness and track displacement.
Highlights
Shape-memory alloys have the distinctive ability to withstand large recoverable strains and regain their original shape after deformation either instantaneously or upon heating [1]
The measurement of top width, taper angle and spatter spatter around the periphery of the channel is done as shown in Figure 4c,d, respectively
The microhardness of the base material interval 319 ± 8 HV, whereas near the laser machined surface was found in the interval 310 ± 11. These was found to be in the interval 319 ± 8 HV, whereas near the laser machined surface was found in the results suggest the These absence of anysuggest detrimental effect ofofthe processing on the microhardness of the interval the absence anylaser detrimental effect of the laser processing
Summary
Shape-memory alloys have the distinctive ability to withstand large recoverable strains and regain their original shape after deformation either instantaneously or upon heating [1]. SMAs, NiTi alloys are most popular because of their better workability and commercial viability These alloys find applications in biomedical implants [2], MEMS (Micro-Electro-Mechanical-Systems), sensors, actuators and antennae [3] because of their high specific strength, toughness, biocompatibility, superior shape memory effect (SME), high wear and corrosion resistance properties [4]. These alloys have poor thermal conductivity and low effective elastic modulus which makes its machinability challenging especially with conventional technologies due to work hardening and residual stresses. Research has been done investigating the influence of cutting tool material on the quality of machining, the means of improving the material removal rate (MRR) during turning and drilling of NiTi alloys [6]
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