Dalam praktik biasa teknik tuangan kacau, komposit matriks logam dihasilkan dengan cara meleburkan bahan matriks dalam suatu bekas kemudiannya leburan logam ini dikacau dengan kuat untuk membentuk vorteks dan bahan tetulang partikel dimasukkan melalui bahagian tepi vorteks yang telah terbentuk. Daripada satu sudut pandangan pendekatan ini mempunyai kekurangan, yang timbul daripada kaedah memasukkan partikel dan kaedah pengacuan. Semasa penambahan partikel ini dilakukan akan berlaku pemejalan setempat dalam leburan tersebut yang teraruh oleh partikel, dan ini akan meningkatkan kelikatan buburan tersebut. Kaedah penambahan partikel melalui bahagian atas ini juga akan memasukkan udara ke dalam buburan yang muncul sebagai poket udara di antara partikel tersebut. Kadar penambahan partikel ini juga perlu diperlahankan terutamanya apabila terdapat peningkatan pecahan isipadu partikel yang digunakan. Proses ini akan memakan masa yang lama terutamanya untuk produk yang lebih besar. Kajian ini mencadangkan satu pendekatan baru untuk menghasilkan tuangan MMC. Apabila semua bahan dimasukkan ke dalam mengkok grafit dan dipanaskan dalam atmosfera lengai sehingga aloi matriks menjadi lebur dan kemudiannya diikuti dengan tindakan kacauan dua-langkap sebelum penuangan ke dalam acuan, mempunyai kelebihan daripada segi menggalakkan kebolehbasahan di antara partikel silikon karbida dengan aloi A359 aloi matriks. Kejayaan penambahan partikel silikon karbida ke dalam aloi matriks telah menunjukkan bahawa kebolehbasahan di antara partikel silikon karbida, dan sifat mekanikal seperti kekerasan dan kekuatan tegangan adalah setanding dengan data sebelumnya yang dihasilkan oleh penyelidik lain. Kata kunci: Komposit matriks logam; tuangan kacau; kebolehbasahan; kekerasan; kekuatan; penyebaran partikel In a normal practice of stir casting technique, cast metal matrix composites (MMC) is produced by melting the matrix material in a vessel, then the molten metal is stirred thoroughly to from a vortex and the reinforcement particles are introduced through the side of the vortex formed. From some point of view this approach has disadvantages, mainly arising from the particle addition and the stirring methods. During particle addition there is undoubtedly local solidification of the melt induced by the particles, and this increase the viscosity of the slurry. A top addition method also will introduced air into the slurry which appears as air pockets between the particles. The rate of particle addition also needs to be slowed down especially when the volume fraction of the particles to be used increases. This is time consuming for a bigger product. This study propose a new approach of producing cast MMC. When all substances are placed in a graphite crucible and heated in an inert atmosphere until the matrix alloy is melted and then followed by a two–step stirring action before pouring into a mould has advantages in terms of promoting wettability between the silicon carbide particle and the A359 matrix alloy. The success of the incorporation of silicon carbide particles into the matrix alloy showed that the wettability between silicon carbide particles and mechanical properties such as hardness and tensile strength are comparable with previous data produced by other researchers. Keywords: Metal matrix composite; stir casting; wettability; hardness; tensile strength; particle distribution.

In this study a plate form of Ti-50.7at.%Ni was subjected to solution annealing at 800°C and 900°C for one hour followed by ageing at 300°C and 400°C for 4 hours respectively in order to investigate the effect of solution annealing and low temperature ageing on the microstructures and superelastic behaviour. It was found that the formation of Ti3Ni4 precipitates on the samples aged at 300°C and 400°C influences superelasticity differently. Increasing the testing temperature up to 38°C generally increases the superelasticity of samples for all heat treatment conditions compared to those tested at 22°C, however the sample solution annealed at 900°C give better superelasticity at 22°C due to excessive plastic deformation at higher temperature.

In this paper Ti-50.7at.%Ni as a commercial material was examined to analyse the effect of annealing temperature on the microstructure and deformation behaviour. It was found that the microstructure and deformation behaviour of asreceived material was affected by the existence of dislocations that was introduced during manufacturing process. The presence of martensite variant and the B2 austenite broadening in XRD spectra of as-received material verified this conclusion. However, annealing treatment has gradually eliminated this effect. The plateau region on stress-strain curve which was absent in the as-received material started to appear and get longer with increasing annealing temperature. Maximum tensile strength was observed in the sample annealed at 400 C for 1 h. Annealing treatment above 500 C transformed the B19 0 martensite to B2 austenite, which leads to a decrease in the tensile strength of the material. Nearly perfect superelasticity was found in the as-received material and sample annealed at 300 C.

Ti-50.7at.%Ni as one of Ni-rich TiNi shape memory alloy is very responsive to precipitation ageing treatment due to the formation of Ti3Ni4 precipitates. This study indicates that this alloy exhibits different transformation sequences under different ageing temperatures. Precipitation of Ti3Ni4 has introduced the formation of intermediate R-phase prior to martensitic transformation. The lack of 2-step R-phase transformation, B2→R1 and B2→R2 transformation in this alloy, suggested that Ti3Ni4 precipitation occurs homogeneously.

Tujuan penelitian ini adalah untuk mengetahui pengaruh temperatur aging terhadap temperatur transformasi paduan Ti-50.7at%Ni. Temperatur transformasi menjadi sangat penting pada material paduan shape memory karena sifat superelastisdan shape memory hanya akan dihasilkan pada temperatur tertentu sehingga membatasi penggunaan material ini. Padapenelitian ini, material diberi perlakuan panas dengan cara solution treatment pada 900oC selama satu jam diikuti denganpendinginan dalam air. Selanjutnya aging pada empat temperature yang berbeda yaitu 300oC, 400oC, 500oC dan 600oC.Temperature transformasi diamati dengan menggunakan Differential Scanning Calorimetry (DSC). Hasil penelitianmenunjukkan kehadiran B19′ martensit dalam struktur mikro material as-received tidak dapat dijelaskan dengan hasil grafikDSC. Hal ini dimungkinkan karena masih adanya pengaruh rolling dingin pada saat proses pembuatan plat yangmenyisakan kehadiran dislokasi di dalam material. Dislokasi ini menyebabkan martensit hadir pada temperature yang lebihtinggi dari seharusnya. Aging pada temperature yang bervariasi yaitu 300oC, 400oC, 500oC dan 600oC menyebabkantransformasi fasa dalam material Ti-50.7at.%Ni terjadi dalam dua tahap, yaitu B2 austenit bertransformasi menjadi fasaintermediate R, selanjutnya fasa ini akan bertransformasi menjadi B19′ martensit.