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The study has compared the effect of gas metal arc welding techniques on some mechanical properties of duplex stainless steel. The samples after welded were given post weld heat treatment (quenching in engine and neem oil). After the analyses, it was established that duplex stainless steel can be weld successfully using gas metal arc welding process (GMAW). Both Lubricating oil and neem oil can serve as quenching medium for post welding heat treatment of duplex stainless steel. The results of the studies also show that welding and heat treatment really affect the mechanical properties of the alloy; the control strength was 811.47 MN/m 2 while that of the welded samples ranged from 177.07 to 257.32 MN/m 2 . The control impact energy was 162.70 J, while that of the welded samples ranged from 38.64 J to 56.20 J. The research also shows that the stress relief heat treatment gives better strength (A 3 = 331 MN/m 2 ) compared to those that were quenched in lubricating oil (A 2 = 329 MN/m 2 ) and neem oil (A 1 = 222 MN/m 2 ), but the reverse is the case in terms of toughness.

In this paper, the mechanical properties and microstructure of die cast aluminium A380 alloy casts produced under varying pressure was investigated experimentally and compared. The results obtained show better mechanical properties i.e. hardness, tensile strengths and impact strengths in the die cast A380 alloy sample that solidified at high pressure when pressure was regulated across five samples of the castings. The hardness of the die cast A380 samples that solidified under different applied pressures varied from 76 to 85 HRN. Also tensile strength, yield strength and elongation of the samples showed an increase with increased pressure. Also the results of SEM and metallography show that at high pressure, structural changes occurred as a fine microstructure was obtained with increase of pressure.