Forming operations are those in which the shape of a metal piece is changed by（）deformation. A.elasticB.plasticC.severeD.slight 正确答案：plastic

A wax or plastic die is appropriate for（） A.sand castingB.die castingC.continuous castingD.investment casting 正确答案：investment casting

A vacancy, caused by an atom missing from a lattice site, is a type of（）defects A.lineB.pointC.spaceD.area 正确答案：point

（）is also called tensile strength, which is obtained at the plastic　deformation region from the stress-strain diagram. A.Ultimate strengthB.Yield strengthC.Fracture strengthD.Compressive strength 正确答案：Ultimate strength

For most cast irons the carbon exists as（） A.cementiteB.graphiteC.martensiticD.austenitic 正确答案：graphite

The（）steels are hardest, strongest, and yet least ductile of the carbon steels， and wear resistant and capable of holding a sharp cutting edge. A.low-carbonB.medium-CarbonC.high-carbonD.mild 正确答案：high-carbon

The noble or precious metals are a group of（）elements that have some physical characteristics in common. A.sixB.sevenC.eightD.nine 正确答案：eight

（）is a homogeneous part or aggregation of material that differs from another part due to difference in structure. A.LiquidusB.SolutionC.PhaseD.Solidus 正确答案：Phase

The cause of cracks in concrete are: stress due to applied（）and stress due to temperature or（）change when concrete is restrained。 正确答案：loads moisture

Concrete used in water-retaining structures or exposed to weather or other severe exposure condition must be virtually（）or（）. 正确答案：impermeable watertight

Workability of（）concrete has a direct effect on the（）and constructibility. 正确答案：fresh pumpability

Concrete is basically a mixture of two components:（）and a（）. 正确答案：aggregates paste