Cu-al-(ni)-mn Shape Memory Alloy Preparation And Performance Study

The processing technological parameters for preparing Cu-Al-(Ni)-Mn-based shape memory alloys by mechanical alloying(MA) and powder metallurgy(PM)and casting have been studied.The structures and properties of the alloys has been studied by means ofρ-T curve,shape memory effect measure,mechanical properties measurement and X-ray diffraction,TEM,SEM and optical observation.Cu-11.9Al-5Ni-2.2Mn(wt%)shape memory alloy powders have been fabricated by MA and powder metallurgy.Faster the rotation speed was,more quickly the diffusion speed of atoms were,however,severaler the degree of agglomerate of the elemental powders were.A laminated structure was formed during MA,and the layer becomes thin with milling time.A single phase of fcc structure was produced after milling for 25h at 300rpm with a ball-to-powder weight ratio 8:1;the average crystallizes size of Cu powder was to 10nm.An amorphous phase was obtained after milling at 300rpm for 100h.The pre-alloyed powders of Cu-11.9Al-5Ni-2.2Mn(wt%)MAed at 300rpm for 100h were compacted at 950℃in vaccum of 10^-2pa under pressure of 30MPa for 2h.The green compact(a relative density over 97.2%)in the evacuation Cu-capsule was hot extruded at 900℃with a extrusion-ratio of 40:1.The metallurgical bonding among the matrix particles has been replaced the mechanical bonding or engagement.The marstensite structure of the alloy after quenched at 850℃for 10min was M18R.The shape memory recovery,η,was measure to be 100%for the as-quenched alloy after 4%deformation.Theηremained 100%as it was subjected to deformation and recovering for 100 times cycling.Theηof the sample has remained 98%as it was subjecting to aging at 40℃for 120 days.The high-plasticity Cu-8.0Al-9.6Mn-0.33Ti-0.17B(wt%)alloy has been prepared by casting.After solution-treaded at 900℃for 10min, furnace-cooled to 620℃,and insulation for 1h,a great deal ofαphases precipicated on the grain;with the increase of insulation time,αphases increased,and the cold-work capability increased,furthermore,after insulation at 380℃for 1h,the cold-working rate could reach 81%,and the elongation modulus could reach 33%.Theηwas measure to be 90% after solution-treaded at 900℃for 10min;and aged at 150℃for 15min, the M_s point was 100℃higher than that of quenched,while theηremained 95%;the martensite structure was M18R.