Effect of heat treatment and mandrel material on precision tube drawing of Ni-Ti shape memory alloy

Review on Advances in Metal Micro-Tube Forming

“…Recent developments in the fabrication of micro-tubes aim in particular to provide improved semi-finished products, with more economic manufacturing processes, for use in microsystem-based applications of medical engineering and microfluidics for heat exchangers. When primarily considering the fabrication of seamless metallic tubes, the investigated technologies can be divided into (a) dieless drawing techniques [5,[21][22][23][24][25][26][27][28][29][30][31][32][33][34][35], (b) process chains, applying scaled-down and partly modified tube drawing [36][37][38][39][40][41][42][43][44][45][46][47], and (c) manufacturing techniques of grooved micro-tubes for applications in heat exchange [43,[48][49][50][51][52][53][54]. Apart from this research into tube manufacturing processes, notable progress was also achieved in the design of the process and tools for the profile extrusion of tubular micro-profiles with a number of channels [55][56][57][58][59].…”

“…3.0 180 BS [39] Multi-pass fluid mandrel cold drawing Magnesium alloy (AZ31) 3.6 610 ME [45] Single-pass mandrel cold drawing Shape memory alloy (Ni(56 wt %)-Ti) 4.0 400 - [37] Hot extrusion, cold-rolling Magnesium alloy (AZ31) <7.71 <900 BS [41] Multi-pass cold drawing (SI, FP) Shape memory alloy (Ti (49.3%)-Ni) <8.0 -ME [47] BS, biodegradable stents; CA, catheters; FP, fixed plug; IN, injection needles (painless, hypodermic); MD, mandrel drawing; ME, medical technology; SI, sinking; ST, stents. a all processes conduced at room temperature.…”

“…The drawing of tubes from Ni-Ti alloys with fixed plugs turned out to be limited to outer diameters of the tubes above 4 mm due to difficulties in joining the plug to the supporting rod, and the forming with floating plugs led to unstable processes, caused by breaks of the drawn material [46]. Investigations based on numerical simulations using hyperelastic and the Mullins effect model, in conjunction with experiments, have shown that the dimensional accuracy of micro-tubes made from Ni-Ti alloys could be improved using brass, instead of copper, for the mandrel material, but that drawing stresses slightly increase [37]. However, the drawbacks of the mandrel drawing of micro-tubes consist in difficulties relating to the removal of the mandrel from the drawn tube and a lower surface quality, compared to that of drawing with fixed plugs [46].…”

Influence of amorphous phase on crack initiation and propagation behaviours in NiTi shape memory alloy based on extended finite element simulation

“…NiTi-based shape memory alloys (SMAs) are widely used in aerospace, ships, ground weapons and equipment due to its shape memory effect and super-elastic effect, which is mainly embodied in aircraft engines, wings, intelligent structures and active controllers [1], vibration and noise reduction stealth components [2] and impact resistant intelligent components [3]. Plastic forming is an essential method to manufacture tube [4,5], film [6], wire [7], rod [8,9], and plate [10] NiTi-based SMAs, and it has significant influence on shape memory effect, superelasticity and mechanical properties of NiTibased SMAs. The research findings have shown that high density of dislocations and even the local nanocrystallization and amorphous are caused by the large degree of cold plastic deformation [11,12], which significantly improves the mechanical properties of the NiTi-based SMAs [13,14].…”