Metal forming is the process that is expected to provide the highest strength of the product with a T-shaped cross-section.

Explanation:
Metal forming is a manufacturing process that involves shaping metal into desired geometries using mechanical forces. It is commonly used to create complex shapes and structures with high strength and dimensional accuracy.

In the given scenario, a rectangular aluminum block needs to be transformed into a product with a T-shaped cross-section. Let's analyze how each process option can affect the strength of the final product:

a) Welding:
Welding involves joining two or more pieces of metal together by melting and fusing them. While welding can be used to create T-shaped structures, it may introduce potential weak points due to the heat-affected zone, which can lead to reduced strength. Welding is not the ideal process for increasing the strength of the product.

b) Casting:
Casting is a process where molten metal is poured into a mold and allowed to solidify. While casting can produce complex shapes, the strength of the cast product is generally lower than that of a formed product. Casting involves the formation of grain boundaries that can result in reduced strength compared to a metal formed product.

c) Metal forming:
Metal forming processes, such as forging, rolling, or extrusion, involve shaping metal by applying compressive forces. These processes work the metal and align the grain structure, resulting in improved mechanical properties, including increased strength. Metal forming is particularly suitable for creating complex shapes with high strength, making it the most appropriate option in this scenario.

d) Machining:
Machining involves removing material from a workpiece using cutting tools. While machining can be used to shape metal, it does not typically enhance the strength of the product. Machining processes can introduce residual stress and may result in reduced strength compared to metal forming.

In conclusion, metal forming is the process that is expected to provide the highest strength of the product with a T-shaped cross-section. It allows for the shaping of the aluminum block while improving its mechanical properties, including strength.